Chapter 8 – Debate with experts andgeneral discussion
p. 183-215
Texte intégral
1Moderator : José Delgado Rodrigues
2Experts : Robert G. Bednarik, Johannes (Jannie) Loubser, Luiz Oosterbeek, Yves Perrette, Stefan Simon, Randall White
3[ The interventions in italic were translated from French to English. ]
4Mr. José Delgado Rodrigues
5We are going to start the last part of our session. I would like to ask the contributors of this afternoon to join me at this table: Roland Lastennet, Philippe Malaurent, Delphine Lacanette, Carmen de las Heras and the discussion participants, Robert Bednarik, Jannie Loubser, Luiz Oosterbeek, Yves Perrette, Stefan Simon and Randall White.
6We can now begin the discussion. All of the subjects can be discussed; questions can be addressed directly to the experts intervening this afternoon and to the persons that intervened this morning in the introduction to this symposium. Perhaps it’s best to start with our invited contributors; if they have something to say in a couple of minutes, a brief introduction to the theme, their thoughts, just to trigger the discussion, which we would like to be lively and open with the audience. I do not think there is a particular order; may I start with you?
7Mr. Robert G. Bednarik
8To begin, I would like to state that I was greatly impressed by the caliber of the presentations today and I would like to look at the problems of Lascaux in an international context, perhaps even in a global context. I would like to remind you that there are many hundreds of decorated caves throughout the world, not just here. In fact, more than half of them are outside of France. For instance, the second largest concentration of cave art—rock art in limestone caves—exists in Australia, and dozens of countries have cave art. This is all the more relevant since all of the cave art conservators of the world are looking for leadership and guidance from the team at Lascaux. As we saw in the last presentation, on Altamira, the team from Altamira have benefited considerably from the experience of Lascaux. We should also remember that conservation practices, applied to rock art in general, throughout the world, have been influenced much more than we may think by the particular developments achieved at Lascaux. Take Chauvet Cave, for instance; would we be as protective as we are of Chauvet Cave if Lascaux had never been discovered and if we had never had the problems we have at Lascaux? I think that these are very important points to consider.
9I think that one important point to make is that rock art conservation throughout the world, not only in caves, has been significantly affected by the developments at Lascaux.
10Mr. José Delgado Rodrigues
11Ok, thank you. Let us listen to the next speaker please.
12Mr. Johannes Loubser
13My name is Jannie Loubser, I am from Atlanta (GA) in the United States, and I thank the organizers for inviting me, even though I do not really have any experience with caves. I have visited many, but I have never really done any systematic studies in caves. I have, however, seen a lot of open-air shelters and the standard practice there is to fill in condition reports. That allows you to look really closely at the site; you also look at the landscape aspects, as was discussed today, but after that you work differently. You then look at the level of the site and then at the level of the decorated panel. This is the kind of question that I want to try to get to. Perhaps someone will address these questions tomorrow, but when you look at the rock itself, the surface, the panel that is usually delineated as a surface by cracks and by bedding planes and things like that—natural features in the rock—those things have their own characteristics: why? Because when you look at things like that, you sometimes see clay formations developing just near the panel, but right on that panel, there is nothing.
14And another thing that I have found when working with people who do chemical analysis in the field is that if you look at any rock surface, vertical surface, you find bands, strips of water flow coming down. And sometimes the strips form little rivulets, but the important thing, I think, is that they transport different salts, because if you do tests vertically or horizontally in the different vertical bands, you will find there are different kinds of salts: chloride, sulfates, calcium oxalates, often barely a meter from each other, and this really affects on the surface of the rock. So this brings me to the question and perhaps people will answer this tomorrow: do the chemical characteristics, the types of salts that you find on the rocks, influence the fungal growth and the bacterial activity? Have these researchers come to together to discuss this, and if this is the case—which I am sure it is—have they synthesized things such as water sources, bedding planes, cracks right above those particular areas?
15Also, the limestone is porous, and it has a smooth hardened layer; is that the case there? I also think that the inclination or the angle of the panel is important. I mean the vertical or horizontal angle, you know, the 45 degree angle, because I feel that could be important. Sometimes dust settles on surfaces that face upward, and at the same time, you find that ceilings are well preserved because there is very little foothold for deposits that can act as nutrients for plant growth. So these are the kinds of variables that I am sure people have investigated at this level but perhaps tomorrow people can give some answers as to that. Because if you do find that natural conditions mitigate against the growth of these things, then instead of using fungicides and stuff like that, one could perhaps try to emulate the natural surface.
16In 1989, I studied in Australia, and I was present at a lot of lectures by French people, conservation specialists that came over and taught us and they hammered it in to us that minimal intervention is preferable, to have interventions that you can repeat and to carry out interventions that are distinguishable from the original stuff. Well, reversible intervention of course is not possible, but there are other solutions, I think. For instance it seems that they followed that at Altamira, which might be the favorable way to go. Thank you.
17Mr. Luiz Oosterbeek
18I would like to thank the organizers for their invitation and welcome Mr. Jean Clottes in particular, as the president of the IFRAO. I am not an expert in the area of prehistoric art preservation either; I deal above all with open-air art.
19I would like to ask two or three questions. To summarize, can we affirm that a strategic part of the problems at Lascaux is due to anthropogenic action? If I have understood correctly, it began with the opening of the entrance and was extended with other actions, including the mechanical system built some years ago.
20Of course, this raises a certain number of issues that go beyond the strict subject of this session. Lascaux is seen as a focal point, for the importance of its art, not only by society, but also by researchers. When you follow the discussions and studies on preservation methods, you realize that society has made a considerable economic investment. Elsewhere we see a tendency to follow in the footsteps of Lascaux, and I wonder to what extent this can be done, both from the financial and social accessibility viewpoints. It is one thing to close one cave, but closing all the others is something else. There are examples. The poor management of Foz Coa created terrible social problems in Portugal. The common opinion was that the archeologists wanted to classify and protect the site by restricting it to about twenty people only, as that was the average number of people who visit it every day. Here we are talking about a 17 km-long site, in the open air.
21The question may not be scientific, but I think there is a relationship between the two in this type of conference. In my view, the conclusion drawn by this symposium could be to continue to ask the French State to keep a close watch over prehistoric art and protect it better, and also to recommend this to foreign authorities. Within the framework of your scientific research, do you also consider the social impacts of your work?
22Mr. José Delgado Rodrigues
23Thank you. And now to you sir.
24Mr. Yves Perrette
25Thank you for inviting me to this round table. I would like to congratulate the speakers for the scientific and educational quality of their papers. I am a geographer and I am therefore going talk about scales. Two aspects of the previous papers interested me in particular, the first of which is the question of monitoring, which has changed between the measurements made in the 1950’s and 60’s and those made today. Is there any continuity between the two? What will the impact of this monitoring be on the scale of our understanding of the cave’s climatological phenomena? This brings me to what, in my view is the most important question, that of observation scales. When an occasional measurement is made, it is very often highly variable in spatial terms. If the measurement is shifted by one meter, you will have chemical changes in the infiltration waters. This is thus a first problem involving the transition from monitoring data to a generalized knowledge of the cave. How can this problem be solved? Modeling allows this.
26The second level concerns large scales. We realize that the cave is in a much larger massif. In the cave, the conditions at the limits are composed of a heat gradient in depth—and we know that in the natural environment the gradient is not homogeneous. It is thus necessary to integrate in these conditions at the limits, the up and downstream effects and of course the vertical heterogeneity of the flows. Is it possible to integrate this in the model?
27As for very small scales, the presentations referred to the cave as a whole. However, the preservation problems are posed at microbial level, at the level of bacteria and fungi. Are we not branching off here towards small scales, where we will no longer observe the same phenomena? For exemple, the equations that govern the thermal and chemical diffusions of CO2 between the air in the cave and the air in the rock are different.
28These break levels seem very interesting to me, particularly to complete thereally rich work that has been done in modeling and to make the best use of your work from the perspective of an integration or continuity between microbiological modeling and dynamic modeling.
29Mr. José Delgado Rodrigues
30Thank you.
31Stefan Simon?
32Mr. Stefan Simon I would also like to thank the Ministry of Culture and Communication for its invitation to this round table. I will now continue in English; that will be easier for me.
33I am very impressed by the presentations given this morning. I want to say something about preventive conservation, from my perspective of working with a large museum collection, and about the challenge that you are facing at Lascaux. I think we can generally divide this preventive conservation into three stages; three phases. The first one is the study of the reaction of objects, sites and monuments to the variable parameters in the environment and to find out whether this reaction or interaction is reversible or irreversible. In the second phase, we try to determine the optimum conditions and in the third phase we try to establish this regime and control it. Unfortunately, and this is my experience in my country, Germany, we devote much more emphasis to phase 2 and 3, and unfortunately we do not devote a lot of emphasis to phase 1, the study of the reactions of the objects. As I said already, I am impressed by how intensively the site of Lascaux has been studied. I think it is not an exaggeration to say that no object or site on this planet has been studied better than Lascaux, for which you have a high density of data. I think the site has no equal on the world scale. You can go back many years, you have climatic data, you are looking at all this information very carefully and I would like to know whether there is any other place on earth where something has been achieved like here at Lascaux. I think that is very important to state.
34I also would like to make a brief comment on the relationship between science and archaeology. I think that it is something that goes back a long time and I would like to give you an example from the early 19th century when a British colleague, Humphry Davy, was sent by the King to Naples to treat burned and calcined scrolls with his new conservation procedure. In 1818, his work culminated in the total destruction of the entire manuscript collection, even before an attempt could be made to read them. I think that was one of the first examples of the interaction between science and archaeology, which was not very fruitful and which was maybe one of the reasons that we have to deal with a great reluctance from archaeologists as regards science. However, at least from my point of view, it became quite visible in your presentations today that there is the need for these fundamental and core sciences, just by mentioning—I think, it was the last speaker— that our knowledge of the situation at Lascaux should be supported by digital methods. She also made a statement that, if I have understood her opinion, “the current configuration is incompatible with the climatic system in place”. And I think that should be taken into account because sometimes also in conservation, we must make decisions and we must intervene and we must realized treatments and I know that there is a certain suspicion of science especially from the archaeological side, but we have to look for valid options. Unfortunately I think that beyond studying, sometimes interventions imply disruptions, and of course mistakes and errors can happen, but I will still leave here with the impression that nothing has been studied as intensively as Lascaux. And I will try to learn from that and go back to Germany and talk a bit about how we could deal with our monuments. Thank you.
35Mr. Randall White
36I would like to carry on in the same vein by admitting that it is true that Lascaux is very well studied. Nevertheless, if I have understood this correctly, the UNESCO list includes several tens of sites in the Vézère Valley, including Combarelles and Font de Gaume, which we are not discussing today. It would be inappropriate for me to pass judgment on their state of preservation, but I do think that they must not be forgotten when we consider what is referred to as the Lascaux catastrophe.
37I would be happy to take up the idea proposed by Robert G. Bednarik concerning the preservation of decorated caves. Having lived in Montignac for seven years, I am pleased to see the town of Montignac and the Dordogne Council being congratulated. Nonetheless, I think that this awareness is only quite recent, and that since the discovery— despite André Malraux’s generous sentiments—Lascaux and the town of Montignac have been seen as cash cows. There was, for example, the idea of destroying the historic buildings in Montignac to provide access to Lascaux. That would be quite inconceivable today.
38If there is one lesson to be learned from Lascaux, I think that this is it. A fair balance must be found between the public interest and keeping the public informed about culture and tourism. This is an issue that the authorities in Dordogne are currently concerned with. One of the very promising solutions for Lascaux remains the construction of a new facsimile of the cave, as a way of preserving the original cave.
39Besides these two relatively general remarks, I have two questions that I would like to ask. I imagine that we will talk about microbes tomorrow. It would seem to me that we have really not talked very much about the question of the current state of the Hall of the Bulls and the Axial Gallery. When you visit the cave, you can easily see the microbes and black spots, even if the areas are not well lit. What is their current state with respect to these flows and the changes of humidity?
40I was nonetheless very impressed by these papers and I would like to thank you for the quality of the research that is taking us in the direction that we want to go.
41I also have a question for Miss Lacanette. You showed us data concerning the state of the cave over the period from 1981 to the present day. What would we see if we did these same studies for the 1996-2000 period? What disturbs me is the coincidence between the situation in 2000, the changes made to the air circulation system and everything that you have shown us this morning. I would like to know exactly when the imbalance first occurred.
42Mr. José Delgado Rodrigues
43Thank you. We already have questions for this afternoon’s speakers. We can start with the questions that were addressed directly to the people that presented. So if some of you, Miss Lacanette, if you have a direct question, maybe if the others think that they have been asked something, please go ahead.
44Ms. Delphine Lacanette
45Concerning the simulation on a larger scale, that is effectively something that we are thinking about and that it should be possible to include, which would mean that we would have to work more with the geologists and hydrogeologists to obtain the data needed to achieve what you have spoken about. I must insist on the fact that we see the simulator as a tool that brings together the different disciplines.
46As for taking a greater interest in smaller scales, either we have to achieve much finer grids—I forgot to say in the paper that at present we have a pitch of 35 cm, and that if we want to consider the cave in its entirety and arrive at a space scale allowing us to introduce microbiological models, that would be rather utopian given the calculation means currently available—or we focus on a more restricted part of the cavity and do it there. Lastly, and this is what I consider to be most worthwhile, we could include models of the walls, that is to say keep our current pitch of 35 cm, and include models that represent what is happening in each 35 cm zone, in terms of what we want to observe, that is to say either microbiological data or more precise thermal data.
47Mr. Yves Perrette
48Insofar as it is a model essentially based on flows, will it remain relevant on the gradient that exists between the airflow zone and the air-rock interface? Or, from a few millimeters to a few centimeters, is there something that does not flow? With a gradient that is generally quite regular, are these the same equations? Can this be integrated?
49Ms. Delphine Lacanette
50They are in fact the same equations. Everything then depends on the precision that we use. At present, what we show by simulation is correct for a pitch of 35 cm and will remain so if we refine it. Then we just have to decide on the next stage: work on calculating powers or work on the introduction of models. In any case, the equations will be the same.
51Mr. José Delgado Rodrigues
52Are there any other questions?
53Ms. Delphine Lacanette
54I’m sorry, I’ve forgotten what Mr. White’s question was.
55Mr. Randall White
56I would like to know if, instead of comparing what happened in 1981 with what is happening at the present time, would it be possible to create slightly smaller periods around the events of 2000.
57Ms. Delphine Lacanette
58Ah yes, that’s it, I’m sorry. In fact, the two types that were chosen— 1981 and 1999-2008—were chosen in light of what Philippe Malaurent showed you earlier on. He has shown that we were observing a change in the cave starting from 1983 or 1984, from the thermal gradient viewpoint. That is why we selected earlier and later dates. In 1994 or 1995, we would have this 1999-2008 type. Perhaps it is true that the choice of terminology was not quite appropriate. It was simply a question of marking the ideas with years.
59Furthermore, we thought it would be interesting in the end to have two configurations: the positive slope or the negative slope. In doing so, we manage to cover everything that may have existed over more than 18,000 years because sometimes the gradients were positive and sometimes they were negative. We gave them type names, with a view to showing that, in the end, there were two configurations and that we were processing them with both those types.
60Mr. José Delgado Rodrigues
61Thank you. Mr. Malaurent?
62Mr. Philippe Malaurent
63I would like to add to what you have said as to whether, finally, the change of machinery was the trigger or not, a hypothesis that was only thinly veiled in other questions. I am going to explain to you the choice of the two dates. Delphine Lacanette has just explained why the year 1981 was chosen; I insisted on the choice of the year 1989 earlier on, that is just before the works. We chose that date because we could not simulate everything. Once again, the time chosen to change the machinery was certainly not the right moment. But, it was only with hindsight that we realized this. To put things rather simplistically, we can say that at that moment, the work served as a catalyst, destroying a balance that was already extremely unstable. We are currently having great difficulties recovering a balance, because nature is not helping us.
64Mr. José Delgado Rodrigues
65Thank you. Does anyone else want to add anything? Otherwise, we can open up the discussion to the audience. Any questions?
66Mr. Jean-Michel Geneste
67Thank you. I would like answer Randall White who asked me what exactly was happening in the entrance areas to the Hall of the Bulls and the Axial Gallery.
68When I spoke this morning I used an expression that was perhaps simplistic to say that, currently, the situation is not as worrying as the black spots or, in any case, that it is no longer our number one priority. In 2001 and especially in 2002 and 2003, the cave was overrun by fungal growth. When we entered the cavity—you asked about the lighting—the cave floor was completely white, covered with Fusarium, and the fungi were beginning to attack the ledges. This is why we spread lime, which will be explained later on.
69Today, that is no longer the situation at all. That is why we look at it differently. This means that, in practice, even if there are some new very isolated growths in the Hall of the Bulls, consisting of what we call “small spots”—points where there are elements that are regularly treated by the restorers—this is becoming increasingly rare.
70In the Axial Gallery, on the other hand, the space is more confined and inaccessible to thermal improvement. This is a space in which, for the last few years, the situation was extremely worrying because there was a combination of white and other molds. There was glair present on the lower parts of the walls, on the calcifications and on the floor. This was a bacterial mucus that we had to scrape off with trowels. We also observed water exudation.
71This part of the cave was in a climatic and biological condition that was quite different from its current state, even if we regularly and seasonally have recurrent concerns, as is the case at the moment. The white mold is not there but, with particular types of lighting that we have learned to use, we observe shiny spots on the wall that warn us of the need for vigilance.
72I hope that answers your question. It is true that the visits, including the one you made some months ago, are made in a dimness that corresponds to the old lighting. The intention is not to dissimulate but rather to limit the amount of light.
73Mr. José Delgado Rodrigues
74Thank you. Sir?
75Mr. Paul-Marie Guyon
76Thank you. This discussion has been very interesting and I greatly appreciated the increasingly clear papers. My question concerns the notion of climatic balance that arises as a paradigm. It seems to me that this must be discussed. As it happens, historically, after the first crisis in the sixties, we had—by chance perhaps—a situation that was climatically balanced and that we have been able to monitor systematically throughout the cave, thanks to the data provided by Jacques Marsal and the temperature and humidity recording protocols. This continued until 1993, I believe. Jacques Marsal noted that the paintings were stable.
77It so happens that at that time, the famous machine that I designed and Mr. Pierre Vidal and my successors at Lascaux developed, was running and operating on demand to maintain the humidity just below the condensation limit in the Hall of the Bulls, where small stainless steel mirrors placed on the wall misted up if condensation was present. As requested by our first commission, we sought to stabilize the parameters so that they would be as close as possible to the initial conditions. The humidity was therefore somewhere between 98% and 100%, and the air and wall temperatures were always constant, to within one or two tenths of a degree. This worked, but in 2000 things changed.
78And now, it seems—both in Mr. Malaurent’s paper and in Miss Lacanette’s work—that we will somehow have to install a new machine that can introduce a slight, favorable imbalance. There may be humidity saturation in the right-hand part of the cave and the temperature is perfectly stable. It is possible that knowledgeable people may decide that these conditions must be changed and the atmosphere dried slightly. This is the solution that will put an end to the spread of fungi. If the committee is convinced that this is what must be done, then let’s do it, let us take the risk and see what happens. No one has discussed this. I therefore cannot see the great problem concerning the two cold spots.
79Given that we do not really know what to do, it seems to me that we should just, for the moment, let the new machine function as it is, improve it and get it to run correctly, rather than trying immediately to create new cold spots elsewhere in the cave, without being convinced that this is what must be done for microbiological reasons. Thank you.
80Mr. José Delgado Rodrigues
81Thank you. Yes, please?
82Mr. Philippe Malaurent
83I am not going to give a real answer. If you present things in this way, the solution obviously seems inappropriate. But that is not the case. We have already given the problem a lot of thought. In her paper, Delphine Lacanette effectively showed that these were pre-existing situations. When groundwater was present, there were drying conditions that caused terrible damage to the cavity, incomparable with what we are proposing.
84Today, when we envisage cold spots, we are referring to a simulation and not a physical reality. We are therefore continuing to look for other solutions that are less invasive for the cavity. However, we are not seeking to create an imbalance, quite the contrary.
85The simulator shows that if someone enters now, it will lead to an imbalance. We are working on eliminating it as quickly as possible, but not too much so, so as not to dry out the cavity in fits and starts. In any case, we are trying to return very quickly to a state of “equilibrium”, a term that I do not like.
86It is therefore not a question of creating an imbalance, but rather of eliminating as quickly as possible the one created by the presence of someone who has entered the cavity, and that is necessary.
87Mr. Paul-Marie Guyon
88I like your answer. Here we are touching on a second aspect of the problem. What happens in this cave when the caretaker, a minister or an engineer comes in, even if it is only to observe and report on the condition of the walls? There is therefore a human presence. This is a specific point, with a specific disturbance, which was already studied 40 years ago. You are bringing it under control—and you are quite right to do so.
89Is this a serious disturbance? I was talking with François Bourges, who is working on Chauvet Cave. This very deep cave has a climate and temperatures that are perfectly stable, not to within a few tenths of a degree like here, but to within one or two hundredths of a degree. It is possible to have some visits to this cave. In Lascaux, if five visitors enter the cavity each day, there is probably no need to do anything at all, because the rock assimilates it in two days. Now you’ll ask yourselves whether this must be compensated for immediately or not. There’s no obvious answer.
90Mr. Philippe Malaurent
91Once again, I am going to propose some answers. You say that in the passage we are talking about, the measurements that I know about, and which have been recorded for some time, show that it takes at least one week, or even two or more, to restore a balance. You have mentioned Chauvet, but that cave’s volumes and depth are totally different. Any disturbance there is spread over a considerable area that does not bear any comparison with Lascaux. Furthermore, the simulator has shown that the humidity disturbance remains trapped.
92Mr. Paul-Marie Guyon
93I maintain that this equilibrium is permanent. If there is any human disturbance, the equilibrium remains. This cave follows the disturbances adiabatically. A slight temperature change does not, in my view, have the slightest effect on the preservation of the paintings and on the microbiology. All this seems rather meaningless. Major changes have an impact, but not these small ones that the cave has integrated. Focusing on the idea of providing climatic assistance seems dangerous to me.
94Mr. José Delgado Rodrigues
95Thank you, I think that your question has now received a clear answer. Any other questions?
96Mr. Yves Perrette
97To complete the answer concerning Chauvet, having seen François Bourges’s measurements and worked with him, I can tell you that the fact there is stability in the cave is due both to the volume and to a turbulent flow. There is stability in major turbulence. There is no turbulence at Lascaux, everything is stratified. That is no doubt what makes the difference between the two caves. You cannot therefore model the way one cave functions on the way another one functions, just as you probably cannot model the way a cave functions today on the way it did twenty years ago.
98Mr. José Delgado Rodrigues
99Thank you. And now you, please.
100Ms. Adriana Bernardi
101I am on the committee, and I am the physicist in charge of measuring the microclimate as close as possible to the rock. The question that you asked earlier on is a fair remark, but a project is currently underway to show whether or not there is a correlation between small and large scales, degrees, tenths and hundredths. We are in the process of measuring all that. It is still a bit early to say, but that could provide an answer to your doubts and your question.
102Mr. José Delgado Rodrigues
103Thank you. And now over to you, please.
104Mr. Jean-Jacques Delannoy
105I am also on the Lascaux Cave Scientific Committee. It seems to me that certain presentations and questions bias the discussions. It is simplistic to focus only on the “famous” new machine, as if it was responsible for everything. We could focus on the machine if the cave’s environment and the environment outside had stayed the same. However, we know perfectly well that the cave’s environment has changed, just like the external environment, in terms of both plant cover and climate. In my view, this climate change factor is important. From the 1980’s onwards, we have observed a thermal spiraling. To my knowledge, there is no microclimate specific to the Dordogne that would allow the cave cannot escape the spiraling that we observe all over Western Europe.
106It therefore seems to me that seeking to restore the initial equilibrium is not the issue, given that the environment has changed. However, we could work on other paradigms around the cavity’s current dynamics, taking into account its condition, the way it functions and the changing external conditions. From there, let’s try to establish a link between conditions that would make it possible to preserve the artworks, as that is effectively the issue.
107It seems to me that the work that has already been done on monitoring, from a hydrogeological viewpoint and from a climatic viewpoint, and by means of modeling, move in that direction.
108Ms. Adriana Bernardi
109I would like to add something to what Ms. Lacanette said about the modeling scale. It seems to me that the data I am in the process of collecting would be useful for validating their work on a smaller scale. I think that many of the questions will be answered over time.
110Mr. José Delgado Rodrigues
111Thank you. Any other questions?
112Mr. Michel Bakalowicz
113I specialize in subterranean waters in karst and I was a member of the committee until 2004. I would like to put back into perspective the work that has been presented to us this afternoon, with respect to what is known generally about what happens in limestone.
114It is a medium that we now know is very complicated. We also know that it had not been studied very extensively until the second half of the 1970’s. The first measurements for Lascaux were made when the knowledge of the medium was really very limited. The choices that were made concerning the measuring and monitoring procedures were made, not at random, but at least in a very intuitive and not necessarily very orderly way.
115We now have a general framework of knowledge, concerning both karst and Lascaux, thanks to the studies that have just been presented. It is going to be much easier to replace irregular observations, but it is essential to continue the observations in the long term, because we can see that there is a certain inertia in the system, as there is for all these limestone massifs. If we do not have any long-term measurements we will not be able to understand the small local variations in space, nor the short-term variations over time.
116This is a long-term job. And it is true that Lascaux is not a laboratory. Nevertheless, it is a place where we are trying to put into application knowledge that was developed elsewhere and we are implementing new analysis methods. We are not simply undertaking research into the preservation of cave art.
117There is therefore an interaction between applied research and the social and economic problems mentioned earlier on with which we, as water specialists, are constantly confronted.
118Mr. José Delgado Rodrigues
119Thank you. And over to you now, please.
120Mr. Michael Petzet
121We have talked a lot about simulation models, but in my view we must also preserve our heritage. It is fantastic that we should have this type of model but, in the end, action is required. We must restore this equilibrium and even undertake reconstruction, in order to return to the situation we had before the disaster in 2000.
122Mr. José Delgado Rodrigues
123Thank you. You now please.
124Mr. Michel Goldberg
125Seen from the outside, it would seem urgent to me to restore the climatic equilibrium rather than worrying about the perturbations to this equilibrium that has not yet been restored. In my view, it is a question of priority.
126I would like to go back to the problem of simulations and address Ms. Lacanette, firstly to thank her for her paper, which was remarkably clear and instructive. I have some technical questions to ask you concerning this simulation. Even though I’m from the Institut Pasteur, I am not really a microbiologist by training. My original training was in physics and I can still remember how to use the Ostrogradski formula to study the airflow around an aircraft wing. The question that I would like to ask you—at the time when I studied this we did not have all the tools that are available today—is the following: within what limits of viscosity, compressibility and diffusion coefficients has the Aquilon code that you use for fluids been validated?
127You showed us images of fast-flowing liquids. The calculations that I did in the past concerned fast-flowing air. For air that is flowing this slowly, where the movements are so slight, the problems of gas diffusion and compressibility are obviously critical. I would therefore like to know on what model, with such low dynamics, the codes were validated.
128Ms. Delphine Lacanette
129I will answer you regarding certain aspects before handing over to the Director of the TREFLE Laboratory whom we have the good fortune to have with us here today and who will be able to answer you much better than I can on this point.
130The calculations are done as incompressible. Air compressibility under these conditions is not necessarily very great. With regard to the diffusion coefficients, the validations were done, whatever the coefficient, for speeds of that order. At least, they were done in similar conditions. The code processes very low speeds up to very high speeds. We also have turbulence models. We do not confine ourselves to precise domains.
131Mr. Michel Goldberg
132You model the temperatures of the air in the cave, is that right?
133Ms. Delphine Lacanette
134Of the rock and the air.
135Mr. Michel Goldberg
136Just for my information, could you explain to me, starting from this temperature scale as a function of the depth from the surface, how you use this temperature to introduce this rock wall temperature into your model and then remodify it? As a function of exchanges with the air?
137Ms. Delphine Lacanette
138You remember the block that we are examining? We plunge the cave into the hill. This block is gridded in a Cartesian way. The grids are small cubes stuck to each other. Of course, given that the geometry of the cave is complex, it does not follow this gridding. To allow us to precisely give the temperature boundary conditions on the cave walls, we thought it would be better to give the initial volume conditions.
139Initially we impose the temperatures as a function of the depth, which is both theoretical and verified by the measurements. At the initial time, we have the temperatures in the rock and the air as a function of the depth only; then, by natural convection, by resolving the energy equation and the Navier-Stokes equation at every point, with the natural convection flows forming, we have the temperatures of the air at each time step and they change over time. In the rock, they of course change much more slowly, because there is not the same degree of conductivity.
140Mr. Michel Goldberg
141But you allow the equilibration of the temperature between the rock and the air on the surface?
142Ms. Delphine Lacanette
143Yes, of course, because the equations are resolved at each point, in the rock, in the air and also at the interface. I am now going to hand over to Éric Arquis so he can complete my answer.
144Mr. José Delgado Rodrigues
145Yes, please do.
146Mr. Éric Arquis
147At Lascaux, we have flow conditions that are just about as user-friendly as you can get for a fluid mechanics specialist. We have a fluid that is a gas, that is to say air. You must not confuse compressibility and the variation of the density with temperature. Compressibility only comes into play when there are highly dynamic flows. You referred to experiments on aerodynamic flows. Indeed, that is hyper-compressible and turbulent.
148Here, it is more laminar—we saw earlier that the order of magnitude of the speeds announced is 0.1 cm to 10 cm; we are quite at ease here despite the length scales. This is the best-case scenario with respect to what we are capable of calculating.
149The complexity is due to the geometry and the way it has to be rendered. There are also questions of a relationship with leakage problems, for example. The karstic massif above is cracked and it is therefore possible that there may be stray flows, but in certain cases, these flows may be of the same order of magnitude as the internal natural convection flows. This morning we mentioned the over-pressure that could generate the movements that were observed in the past. The model available to Lascaux makes it possible to take this into account. For example, the massif can be seen as being permeable, provided we know its approximate characteristics. It is clear that we are not going to reduce this down to the scale of a crack.
150We therefore have everything we need to make increasingly complicated simulations.
151I am going to answer the second question in a slightly manner than Delphine Lacanette. The coupling occurs naturally. There is equilibrium, and conservation of heat flows between the solid and the fluid— this is resolved by the same digital methodology. Implicitly, we express the continuity of the temperature and of the flows, whether they are convective and conductive on the fluid side. This is of course very convenient because, for example, we can modify the nature of the solid massif, make it heterogeneous, and obtain exchanges that are slightly more sophisticated and radiative on the surface, but this time with the atmosphere. All this can be done naturally.
152That being said, here as in any experiment, it is then necessary to provide input, use the right parameters and have correct knowledge of the characteristics of massifs.
153Mr. José Delgado Rodrigues
154Thank you. Any other questions?
155Ms. Laurence Léauté-Beasley
156As I understand it, the simulator is a research tool. However, you also say—and this is what I want to focus on—that it is a decision-aid tool. This simulator is not yet perfect, because you have not yet entered all the data to make a model that is absolutely identical to the cave. Nevertheless, you construct scenarios based on this simulator and you draw conclusions from a set of data. How are you going to apply these scenarios, which may be approximate, to a very fragile cave inside which an approximation could be hazardous?
157Ms. Delphine Lacanette
158I must have expressed myself poorly, because that’s not exactly what I meant. Of course, there will never be a model that reproduces the real situation down to the last detail. The model is useful because it allows us to prioritize the problems so that we are convinced that the effect seen in the cavity is linked to such and such a parameter.
159We are not seeking to model everything in one go. When we consider the temperature gradient alone and when we observe the convective flows inside, we know—to put things simply—that they are linked to the temperature.
160Furthermore, the results are established. Obviously, the hypotheses that we have put forward were the result of consultation; they were not chosen at random. We do not leave aside any parameters that could have a significant impact.
161When we say, for example, that the air circulates today at speeds ten times lower than in 1981, we are sure of what we are saying, because that is only linked to natural convection. Obviously, we set aside the hydrogeological and microbiological phenomena; of course, they do not enter into the framework of the model, but they do not have a direct influence on convection.
162The simulator is far from being a magic tool offering a solution for everything—and I don’t think that is what I said. We know what we put in and we know what we get out of it. We obtain information that is commensurate with what we put in. We do not imagine drawing any conclusions on elements that have not been introduced.
163Ms. Laurence Léauté-Beasley
164It reassures me to hear you say it. Nevertheless, my question was relative to the application of the simulator to the cave. What conclusions can be drawn from that and how can these conclusions be applied to the cave? That was my question and you have only answered it partially. You have said you only draw conclusions in relation to the information you enter, but you haven’t said anything about the relation between the conclusions and their application to the cave.
165Ms. Delphine Lacanette
166I am going to try to reformulate my answer by taking a precise example. The committee informed us that the climatic equilibrium in the cavity was apparently not the same in the 1980’s as it is now. We therefore examined the question and used the simulator from the thermal viewpoint, with the consequences for the speeds, resolving only the energy and Navier-Stokes equations to obtain the temperature, speed and pressure. We then answered the committee, saying that, in our opinion, the speeds had been divided by 10. The tool’s work stops there, and this is what makes it a decision-aid tool, a tool that we consider to be useful as a preventive preservation tool.
167Of course, it is not us who draw the conclusions and make the decisions. Perhaps the biologists will then tell us that, in view of their knowledge of a given event, the fact of having divided the speeds by 10 could have an impact; perhaps the hydrogeologists will give us other information. This might also help the conservators to make other decisions. The simulator is simply—and I insist on this point—a decisionaid tool, because all it does is propose results with respect to the different scenarios. And that is where it then helps application.
168Ms. Laurence Léauté-Beasley
169May I ask one last question: to what extent does this simulator contribute to the decision concerning the design of the new machine?
170Miss Delphine Lacanette
171That is what I was trying to show in the last part. The results concerning the control of humidity and heat in the cavity are relatively recent and we are carrying on with our research. In concrete terms, we were asked to find alternatives. In that respect, it’s even simpler. It is really a question of scenarios. We are working with a design consulting firm that proposes ideas to us, and we test the positioning of the hot and cold spots, and different surfaces and positions, then we observe the way the cave reacts.
172That was done after having verified, unfortunately, that the current climatic regulation system was no longer suited to the climatic configuration as it is now. Philippe Malaurent has demonstrated this to you in theoretical terms and by simulation.
173Mr. José Delgado Rodrigues
174Thank you. I think Philippe Malaurent would like to say something.
175Mr. Philippe Malaurent
176I am going to exaggerate slightly and be a bit provocative. Let’s imagine that we manage to know all the parameters contributing to the climatic and biological system of Lascaux. Let us also imagine that I am capable of setting out equations on all those parameters, and that I have a computer that is sufficiently powerful. I run all this and I am very pleased to obtain a result that is going to imitate nature perfectly. If I looked for a model at the outset, it was because I did not know how nature reacted. It would therefore be highly likely that I wouldn’t understand the results given by the model.
177One of the advantages of simulation is precisely that it can be used to isolate each parameter and determine their significance, to realize that what is important in the question posed is one or other of the parameters. We put the others aside temporarily, but that does not mean that we do not keep them.
178Furthermore, we try to give expert opinions among the other opinions, which may be completely contradictory, and we accept that perfectly. We then have to reach a joint decision. As experts, we are only in a position to express ourselves on the thermal issue. Tomorrow, we will examine the biological aspect and it is clear that the imperatives will not be the same. We must then somehow combine all these demands.
179Mr. José Delgado Rodrigues
180Thank you. I think that is clear now. Mr. Bouchenaki?
181Mr. Mounir Bouchenaki
182First of all I would like to thank this afternoon’s contributors who have presented to those of us who are not perfectly familiar with the cave’s situation the hydrogeological context, its climatological problems and the problems of simulation. We have also listened to an extremely interesting paper from Ms. Carmen de las Heras. Has a comparative study also been made between the situations of these two caves, to define how we could draw inspiration from the lessons that have been learned from the work accomplished at Altamira?
183Ms. Carmen de las Heras
184I must say that it is difficult to carry out a comparative study, because this cave is a whole different world. The Lascaux experiment has been extremely important for us. Our work is directly inspired by the work carried out here. Perhaps the method is different, because our action is currently one of prevention and not of direct intervention. This is a preventive action involving scientific analysis and knowledge of the microbiological parameters. We have adopted a position of passive resistance in the face of the microorganisms. We are currently taking measures to beseige the enemy. This is a strategy-based war.
185Mr. Mounir Bouchenaki
186Thank you for your answer. What I meant to say was that it would be particularly interesting to carry out this comparative study with regard to the methodological issues. May I remind you that when I was Director of the Heritage Directorate in Algeria, in charge of the protection of the Tassili rock paintings and engravings, I called on the experts from Altamira, as well as those from Lascaux. Of course, the situation was totally different, as we were in a rock shelters in a dry semi-tropical climate. Nevertheless, it was important to discuss the methodology of the approach to the various parameters, as demonstrated by this afternoon’s papers.
187Mr. José Delgado Rodrigues
188Thank you. Mr. Vidal, please.
189Mr. Pierre Vidal
190I am a former Ingénieur de Recherche at the LRMH and I worked at Lascaux over more than half a century. My question is for Mr. Malaurent and Ms. Lacanette. Since a laboratory cave without any paintings is at last going to be placed at our disposal, have you considered conducting the cold spot experiment in this laboratory cave, and therefore away from the painted areas?
191Mr. Philippe Malaurent
192For the moment, anything is possible. The cave that has just been chosen is intended to be a test location so it could be used to undertake cold spot tests. The economic problems involved in putting the system in place, in reply to what I heard earlier on, are not under our competence or control.
193Mr. Pierre Vidal
194You would just need to find a refrigeration unit—like an electricity generator—that could be placed in the cave. Once installed, the price of the convectors would be the same whether they were placed in Lascaux or in any other cave.
195Mr. Philippe Malaurent
196I am perfectly confident as far as the technical aspects are concerned, especially as we have the backing of a design consulting office. Everything is possible and conceivable. Nevertheless, it will be necessary to set limits, but it is not for us to do that.
197Mr. Pierre Vidal
198Okay, thank you.
199Mr. Thomas Warscheid
200I am also a member of the Scientific Committee. I permit myself not only to ask your opinions, but also to ask you about facts. As a microbiologist and ecologist, we have seen in our studies during the last two years that there is very clear proof of a shift in the microflora from fungi, which prefer a high humidity level on surface, to organisms which prefer a lower level of humidity. This is very clear when we look at the taxonomy of these fungi. As Mr. Loubser said, there is an influence from the materials; we know that is the case with stone, we know that it is the case with all kinds of materials, they present a different porosity, different pore system distribution, and we have seen that. At Lascaux we see it the most in fractures, we see it close to clayey fissures and we see it on crumbling surfaces. So much for the introduction.
201I know that moisture and nutrients are important but, since we have seen that nutrients are present, we can discuss biocide treatment. However, I do not think that this is a real subject for discussion. We should discuss moisture. What is the aim of this explanation? I wish to have a clear answer to the following question: are there data, are there indications, that we have a slight desiccation happening on the surface? I’m not talking about the humidity in the air. I’m talking about the surface moisture, because the organism, the melanin producing fungi, prefer conditions with a reduced moisture contact in comparison to ferzyme, which likes to swim in water.
202We have an indication in terms of microbioecology that there is a shift and I would like to know whether these data exist. And before you answer this question, let me give two clarifications that I would like you to consider when you answer. We did a biocide treatment after extensive discussion in January 2008. And shortly after this treatment, we found 150 liters of water near the machinery. I call that very effective machinery. It was pretty quick and I do not know whether the machinery really knows when to stop in order not to desiccate the surface much more than we can accept for the microflora.
203The second point is what happened to the Bauer airlock? I know that the Bauer airlock was installed at the time to separate the Hall of the Bulls from the Gallery to avoid spreading algae and bacteria to the other parts of the cave. It was an airlock, it had two doors, and these two doors were removed; in 1996, the first and in 2006 the second one. I know it had the function of separating these two rooms but on the other hand, it was made of plastic. And you can imagine that a cold plastic surface functions like a cold front, like a condensation point, so it was removed. I would like to know whether you have any elements indicating that you could do that so easily, without considering the later development of fungi. I ask this considering that after the second door was removed in December 2006, the spread of black fungi was really accelerated.
204The last point is that some climatic hydrological data were presented today, and that is the exterior conditions probably also have an impact: rainfall levels are decreasing, and so the tampon, as the speaker called it, has prevented the cave from getting more moisture, not forgetting the machinery itself that extracted too much so that these organisms could spread on the surface. In conclusion, after having spent two years studying this cave, having been there practically every four weeks for the last six months, I have the impression that the cave is suffering from desiccation. It is a slow desiccation but of course favorable to the spread of melanizing fungi. I would like to know whether you have any indications, whether you can have been able to obtain from the simulations or from measurements, any kind of data that might give us proof of this, or whether this is only a hypothesis from microbiologists who have seen the various shifts in the microflora.
205Mr. José Delgado Rodrigues
206Does anyone want to answer?
207Mr. Philippe Malaurent
208I will be able to answer only partially because, once again, I do not have any exact answer to give. When we removed the second partition—the first one had been removed, as you reminded us, some time ago—it was essentially at the request of the restorers, because the connecting joints were contaminated. We were asked to determine with the simulator whether the partition could be removed or not. We answered, from a strictly thermal viewpoint that as the cavity was confined and the air stratified, its presence or removal wouldn’t change anything. We did nevertheless take the trouble to point out that care would have to be taken to ensure that there was some sort of compartment. However, it was a theoretical warning because the airlock already did not fulfill its functions, as the second partition had already been removed.
209Furthermore, the condensation surface also revealed what was happening inside the cavity. You just have to read the reports to see that, at that moment, the Passageway was damp for a large part of the year, in particular, what we call the “Hippopotamus’ Head”, which was dripping wet.
210But, it is true that since the airlock has been removed, it no longer trickles with water. That’s where we need the biologists, and that brings us back to Mr. Guyon’s question: what is the impact at biological level of what we are observing? As I said earlier on, we can only propose our expertise, but it is not the only one to be taken into account.
211Mr. Thomas Warscheid
212As I have already said, the Bauer airlock had been installed, but it had absolutely no purpose. What we saw when we looked at the plastic surfaces, was water dripping from the surface in large quantities. I imagine that it was like a trap, or like a barrier, retaining the moisture. Some moisture managed to escape regularly because the door was very often open. But the door frame occupied about 70% of the section of the entry to the gallery. The wall of the airlock must thus have functioned by sending some of the moisture back into the gallery and maintained a stable humidity level in this area. I only wanted to raise this question before the installing of a new condensation point. I would like us to consider the possibility of obtaining confirmation from the microbiological data that we have a shift to low humidity level fungi. And I would like to know from the climatologists, before we carry out any other kind of intervention again, whether we are able to achieve equilibrium. We talked about the equilibrium but we do not know where we define it, whether it is 99%, 98%, 97%. It seems to me that the level of humidity that we now have on the surface is too low because it favors the melanin producing fungi.
213I would like to emphasize that we will never get rid of microorganisms in the cave. We will only have a chance—I hope--of eliminating melanin producing fungi because they are deteriorating the paintings. We will never get rid of the organisms. And we know that in the situation we are now in, that it is very difficult to clean melanin off a surface. We know this from the project we did last year and the conservators are even divided as to whether we will be able to succeed with cleaning. I raise this question therefore because we need to clarify the situation and to act in order to limit the growth of melanin producing fungi as quickly as possible, because the melanin cannot be removed easily.
214Mr. José Delgado Rodrigues
215I think that the position is clear.
216Mr. Philippe Malaurent
217We have been talking about humidity for quite some time now, and we must be precise when we use this term. Are we talking about absolute humidity or relative humidity? It has been said that the relative humidity remains, in all cases, somewhere between 98% and 100%, and I suppose that Adriana Bernardi arrives at the same conclusions as I do using different measuring processes. It is therefore absolute humidity that we are discussing.
218Given that, on average, the temperature has risen, the humidity is much greater than in the past. Unfortunately, we cannot do much about that and must put up with it.
219That being said, when we propose to extract the humidity we mean the humidity introduced in excess by exceptional visits, and not the humidity in equilibrium. It is then up to you to tell us whether this humidity is of use to you or, on the contrary, unwanted. This is a biological problem.
220Mr. Thomas Warscheid
221We are in a specific situation in Lascaux. Normally, when we work in museums, in archives and so on, we try to lower the humidity down to the level of 65 or 60%. This is not possible in Lascaux. Now, we have to determine how we reach an upper level that is appropriate for bacteria and some other fungi that do not damage the surface and whether it is possible at this level to eliminate the melanin producing fungi. I think this is an important issue, and we must find a solution and get this melanin problem under control. Another point I would like to mention is natural ventilation: including when we say we are able to lower the humidity, natural ventilation is my first recommendation in the case of archive depositories. But I am careful in the case of Lascaux; I want to have very slow ventilation because otherwise we risk surface desiccation. This is exactly what I do not want after having now observed this cave in great detail over two years.
222Mr. José Delgado Rodrigues
223Okay, thank you. Yes, please.
224Mr. Michel Goldberg
225What I am hearing about the humidity bothers me a bit. Is the humidity you are talking about measured or simulated, or is it simply water that runs off the head of the rhinoceros paintings, as you said?
226Mr. Philippe Malaurent
227This humidity has been measured—as well as possible, because when the relative humidity is situated between 98% and 100%, it is very difficult to obtain very reliable measurements, especially in such environments. Mr. Guyon certainly did everything that had to be done to make that possible; in any case we are trying to get as close as possible and that’s no easy matter.
228We continued to measure it until 2006 or 2007. At present, it is only measured from time to time, because we use psychrometers fitted with small fans that are liable to disturb the muslin sleeves, for example, and create biological problems. We decided not to take any risks and stop the continuous measurements—especially as the humidity does not vary in the minutes just after it was measured. We now only do verification measurements from time to time.
229The simulator does, however, calculate them and we then make comparisons. Part of the measurement is made and, which validates each time the small retained model that we enter into the simulator, because the simulator requires continuous measurements in space that we are not able to obtain. Therefore, the only way left involves making interpolations around the point that we can obtain. There is therefore a controlled aspect and a theoretical aspect to the measurements.
230Mr. Michel Golberg
231Are these points at least close to the areas in danger?
232Mr. Philippe Malaurent
233When the network was complete, there were about ten humidity measurement points in the cavity.
234Mr. José Delgado Rodrigues
235Thank you. Max?
236Mr. Max Schvoerer
237I am a physicist and Professor at the University of Bordeaux, where I have had the opportunity to set up a research center working on cultural heritage materials. But I am here in a different capacity, as observer for the Council of Europe’s intergovernmental major hazards EUR-OPA agreement. This illustrates the extent to which the international community is beginning to take an interest in this type of problem.
238I wonder whether we are not encroaching on tomorrow’s meeting. Indeed, we have talked a lot about the victim but, besides naming them, the guilty parties have hardly been mentioned. There is a keyword that I would like to have heard: what is the metabolism of these fungi? Is the current situation in the cave favorable to them or not? This will be discussed tomorrow, if I am not mistaken.
239Furthermore, the European Commission currently attaches a great deal of importance to the fact that our cultural heritage, in the broad sense, could be a marker of the climate change that has taken place between the 1940’s and the present time. Butt—and this has been said several times this morning—perhaps the changes in the climate outside the cave have an impact on the cave’s parameters. I feel that that this is an area that should not be ignored.
240Mr. José Delgado Rodrigues
241Thank you. That would appear to be more a remark than a question.
242Ms. Valérie Plagnes
243I was wondering, with respect to the contribution on Altamira, whose approach I found to be courageous, whether studies had been conducted on the outside climate. Have you observed the same thing as at Lascaux, that is to say rising temperatures, with a possible impact on the climatic configuration inside the cave?
244Ms. Carmen de las Heras
245We are currently in the process of collecting the data from 1940 to the present day from the weather station in place at Altamira. We have observed a reduction in rainfall and an increase in the outdoor temperatures. Nevertheless, it is not possible for the moment to identify the impact of the outside climatic variations on the inside of the cave. Although we know that the external temperature has risen by half a degree, this rise is imperceptible inside. Altamira does not have a large number of connections with the exterior. Perhaps the cave has not absorbed this additional half degree from the outside?
246Mr. José Delgado Rodrigues
247You would like to ask a question?
248Mr. Paul-Marie Guyon
249My question concerns the cave’s ventilation. Philippe, you have not mentioned the so-called natural ventilation. In the 1960’s, we observed convection currents. When the barometric pressure fell, air came out of the cave with the CO2 through the Shaft. That completely renewed the air in the cave, because when the pressure rose again, it was the outside air that entered.
250Has this ventilation been blocked since the Shaft was blocked? In any case, there remains at least one source of ventilation. The cave has contacts with the exterior and cannot be placed in an under- or overpressure situation. If there is a pressure drop of 10 mbar in a volume of 3,000 l, that means there is 300 m3 of fresh air entering from the outside through all the interstices. In the winter this fresh air would be at 0°. It would go down the stairwell, down to the bottom of the Axial Gallery. That’s what we would expect. Do you take this into account? Lastly, isn’t there any other natural ventilation besides that, via the Chamber of the Felines or elsewhere?
251Mr. José Delgado Rodrigues
252Thank you.
253Mr. Philippe Malaurent
254At present, the model does not take this into account, but we did wonder about this at an earlier stage. We have, ourselves, measured these exchanges, thanks to the runners that you are aware of in the walls of the Hall of the Bulls. When you close them, there is a 5 cm circular hole that makes it possible to measure the exchanges perfectly. We have been able to measure these exchanges at the time of large decreases in atmospheric pressure. We have calculated them and Henri Schoeller, who had already done this, showed that the speeds were absolutely ridiculous compared with the convections that took place at the time.
255Furthermore, this concerns a change of volume, so much so that to begin with, the volume of the space dilates or retracts. There is therefore no reason why the center of gravity should move. I do not really believe in the argument that the outdoor air renews the air inside the cave, but I may be wrong.
256Mr. Randall White
257The decision to remove what remained of the Bauer airlock was, I hope, made by the committee.
258Mr. Philippe Malaurent
259Yes, that was the case.
260Mr. José Delgado Rodrigues
261Any other questions?
262Mr. Pierre Vidal
263I would like to make it clear that I was still working when the first Bauer airlock partition was removed. It was done to make it easier to introduce future probes for the system that Mr. Malaurent subsequently put in place.
264Mr. Philippe Malaurent
265May I react immediately, Mr. Vidal. That’s impossible. And why remove a partition to pass a wire hardly 5 mm wide?
266Mr. Pierre Vidal
267I will tell you why. At the time, there were several wires and the hatch providing access to the sheaths was situated between the two partitions.
268Ms. Laurence Léauté-Beasley
269I appreciated the discussion between Mr. Malaurent and Mr. Warscheid, which is the reflection of a very useful dialogue between two very important areas of activity in the cave; hydrology and the microbiological ecosystem. You depend on each other to find a solution and make a decision. What is the decision-making process in the scientific committee? How are the decisions reached?
270Mr. José Delgado Rodrigues
271Over to you, as Chairman of the Committee…
272Mr. Marc Gauthier
273This process is a bit like what you are seeing at this very moment. The dialogue that you appreciated between Mr. Malaurent and Mr. Warscheid is the usual dialogue that takes place in the committee. When a decision has to be made, the difference lies in the fact that, starting from the presentation of the various aspects of a dossier, or of an item of data, the discussion is then opened up to all the committee members, so that all specialist areas can state their point of view. It is on the basis of the summary that is then made that the committee— or more precisely its Chairman—comes to a decision. The Chairman then puts forward the proposal and it is the Minister of Culture, or his representative, who makes the decision. However, this is done more quickly than in the past, as I explained this morning. There you have the decision-making process in a nutshell.
274Mr. José Delgado Rodrigues
275Thank you.
276Ms. Laurence Léauté-Beasley
277There is therefore a discussion, but it is you, the Chairman, who makes the decision, right?
278I have a second question I would like to ask you. This morning you spoke of the advantage of having a large committee like we have here today. You said that the fusion between the administrative and scientific sides made it possible to reach decisions quickly, that in 48 hours a decision could be reached. How can you carry out an impact study in 48 hours before making a decision leading to an intervention, which is what UNESCO asks for in its requests?
279Mr. Marc Gauthier
280Naturally, what I have described as being the operating mode is the joint decision-making mode. The impact study is another thing. That is a task that is carried out on-site. Gradually, as things progress, there comes a moment when the conclusions are presented to the committee. It discusses them and this leads to a decision being made. There is, of course, no question of carrying out an impact study in 48 hours; that would be a farce. That is absolutely out of the question. An impact study takes months to complete.
281Ms. Claire Gervais
282I belong to the Smithsonian Institution in Washington. If I have understood this correctly, there was equilibrium in 1981. It may have been metastable but it was an equilibrium all the same. We are currently in a situation of imbalance, or at least of a different balance. I would like to go back to the three different causes that can be suggested to explain this: the change of climate system in 2000, the removal of the Bauer airlock partition in 2006 and the impact of the climate outside the cave. I would like to know whether a distinct weight could be attributed to each of these three causes, to see whether it would be possible and wise to return to the pre-2000 equilibrium.
283Mr. José Delgado Rodrigues
284Does anyone consider they are well-placed to review this issue? Mr. Geneste?
285Mr. Jean-Michel Geneste
286I am not necessarily well-placed to review the situation and provide the right answer. However, to answer all the same, concerning the hierarchy of the three parameters mentioned, it seems to me that they took place at three different moments in the same process. The first one to occur played a predominant role from the chronological viewpoint with respect to the others. At the present time, it is clear—and I think that is the view I conveyed this morning—that it was the machinery installation work that was a triggering factor and that in itself was multi-factorial. After that, we had put a process in motion. From then on, all we did was to intervene in that process. It would be true to say I would not place these three parameters on the same level. Let’s be clear on this, the triggering factors played an initiating role. Since then, we have worked for a very long time to recover an equilibrium in Lascaux that was already artificial.
287The logic of our approach and the philosophy of what is being undertaken at the present time in the cave—Including what is highlighted by the climatic studies and the utilization of the simulator—are based on one principle: trying to keep only one logic. We have a system that allows us to manage or assist, at certain moments, the climatic equilibrium in the cave. We are trying to keep the same principle, the same logic of cold spots and of arrivals of cold water. Our principles have not changed much and our coherence is moving more or less in that direction. We are trying, moreover, to stay within a range of interventions that do not deviate from what we have managed to do for such a long time.
288Mr. José Delgado Rodrigues
289Is this answer sufficiently clear for you?
290Mr. Michael Petzet
291Thank you. I only wanted to say that humidity in conservation in general is the main parameter. The simulation of the temperature is only in relation to the question of humidity. So I am a bit shocked to hear that there is danger of dryness. This is as dangerous as too much humidity. I had to work with our Chinese colleagues on the Emperor’s army; there were terrible problems from humidity coming down from 100% to 85% to 87%. Then at 87% all the polychrome ensemble fell to pieces. Humidity is the unavoidable subject of discussion if we are talking about conservation; humidity is important. If you intend to make another model simulation of humidity, I hope that references on the humidity from the last 100 years will be furnished.
292Mr. Philippe Malaurent
293Apparently, something has not been made clear. The simulator takes the humidity into account. Indeed, that is one of the essential results that have been shown. For example, in the 1980’s, the condensation tended to occur at the ceiling level whereas today it is more common at floor level. That is a known fact. You just have to read the daily reports of the technicians to know that at present, when you enter the cavity, you can see that the water tends to run slightly on the floor, whereas in Jacques Marsal’s day, they looked for condensation on the ceilings. The simulator therefore takes the humidity into account, and that is why earlier on we had a relatively interesting debate. We are fully aware that we cannot lower the level of humidity and that is our essential problem. It must be maintained between 98% and 100%. There is no ambiguity on that point.
294Mr. José Delgado Rodrigues
295It is therefore clear that humidity is included in the model.
296Mr. Michel Bakalowicz
297We are talking about humidity, but we must reach agreement on what this term means. There are two types of humidity: the humidity in the air and the humidity on the walls. The wall humidity depends on the humidity in the air and on what is contained in the rock. It appears to me that you are not for the moment capable of taking it into account in your simulator, just as the hydrogeologist is probably not capable…
298Nevertheless, we are sure that part of the humidity comes through the rock. There is everything that comes out of the little spring at the entrance, and also everything that passes through the micro-porosity, and we are not able to control this important factor for the moment.
299Mr. José Delgado Rodrigues
300Jean-Didier, please? Can you complete this answer?
301Mr. Jean-Didier Mertz
302I work at LRMH. The question you are asking is indeed one of the goals of the current “Microclimate-Microbiology” research program. It seems to me that Roland Lastennet has already given some information on certain parts of the project. In the places where we have been able to obtain a tiny sample, we observe that the pore threshold in this type of material is of the order of 0.03 micron. That means that, at 97% relative humidity, it is virtually saturated.
303On extremely compact materials such as Coniacian limestone, we can practically consider that there is a film of water covering the whole wall. That said, I imagine that it is completely different in the Passageway, because there we have structures that are much rougher and contain more sandstone. There are also pore structures that, unfortunately, have not yet been determined, due to lack of samples.
304Mr. José Delgado Rodrigues
305Are there any other questions?
306Ms. Adriana Bernardi
307In the “Microclimate-Microbiology” program that Mr. Mertz mentioned, we are effectively in the process of measuring all the questions that you are raising on humidity. Perhaps, sometimes, you are focusing a bit too much on the large scale of this simulator because that’s what you have heard about.
308We are in the process of taking these measurements as close as possible to the rock, with very fine, purposefully built instruments. These measurements are therefore in line with a whole series of other pieces of information that fit into a larger scale. We are working on two scales, one that is very small, and the other very large, where the simulator serves no purpose.
309All these issues are being examined and unfolded, as are the points raised by Thomas Warscheid, such as the drying out which, as we have seen, changes the microclimate. We are therefore trying to see whether there is any correlation with microbiology.
310Mr. José Delgado Rodrigues
311Thank you.
312Mr. David Summers
313Thank you Mr. Chairman, I am the president of the International Show Caves Association. I can assure you that the world of show caves is watching you closely. The problem you have in Lascaux is not prevalent in the other show caves in the world. So the notion that was put forward earlier this afternoon, that maybe your caves should be closed down is not valid. What we have here though is a question I would like to ask because in dealing with show caves, one of the first things you look at is the topography above the ground, and Altamira has given us a wonderful example and I applaud them for their work in this regard. I would like to ask the first question: what studies have been made of the topography above and beyond the cave itself? That is the first.
314Then Mr. Chairman, I can direct a question across the hall, Jean- Michel told us that different types of lighting have been used and again when you are dealing with lamps and flora, there are set parameters that you follow in a show cave with lighting. Could you tell us Jean‑Michel, what type of lighting you have now installed? So there are two questions, thank you.
315Mr. José Delgado Rodrigues
316Thank you. Jean-Michel?
317Mr. Jean-Michel Geneste
318During the work phase, besides the flashes for taking photographs, we used batteries of neon lights of the order of 60 W to provide the lighting.
319At present, since we know and are wary of using any energy inside the cave, we are in the process of obtaining batteries of LED lights, which are really are cold.
320Mr. Jean-Jacques Delannoy
321May I come back to the discussion of the international scientific committee? I understand perfectly the highly exacting level demanded at Lascaux Cave for studies and decision-making. But can we expect the impossible from a scientific or interdisciplinary perspective? There are research fields concerning the conservation of decorated caves that are poorly, or not at all, covered from a scientific point of view.
322It is important to emphasize that the community of researchers who are working today in subterranean environments is very small, whatever the countries. In the past, this very tiny community was split into disciplinary fields, so that each one approached the cave accordingly as an expert in his or her own discipline, which divided the community even more.
323Today, we are seeing a paradigm shift and a different way of functioning that is relatively significant. We are increasingly developing a comprehensive approach to cavities, at the disciplinary crossroads between archeology, hydrogeology, climatology, etc. In this way, the work accomplished in the scientific committee on the Lascaux, Chauvet or Altamira caves are precursors for the development of this new interdisciplinary scientific community. Interdisciplinarity takes time; it cannot be established by decree, and this can clearly be seen in all the fields of research that exist today. Perhaps it will take five, ten or twenty years to construct and the discussions of Lascaux Cave Scientific Committee are creating this community.
324I hope that this symposium will also be a strong signal for the development of this interdisciplinary approach, which is today something that must be put in place if we are to work on decorated caves, with modern modeling and measuring tools, to make it possible to verify the hypotheses that have been put forward over time, by means of environmental monitoring, etc.
325To achieve that, incentives will of course be needed, but the researchers will also have to dare to work in a different way on cavities. It appears to me that we are in this dynamic and I do not think it is possible to compare the before and the after, because we have changed the way we work.
326Mr. José Delgado Rodrigues
327Thank you. Over to you, please.
328Mr. Michel Clément
329I am the Director of Architecture and Heritage Directorate at the Ministry of Culture. I would like to say a few words on how the scientific committee functions, on how it is evolving, and also on the budgetary aspects.
330Concerning the decision-making process, the way the committee works at present is very typical of heritage disciplines in general. The committee deliberates in an extremely free way. The role of the Chairman is, of course, to organize the debates, encourage synthesis, try to reach agreement or obtain a majority—when there are confrontations that are not only necessary, but also indispensable for furthering knowledge. In the end, the Chairman proposes solutions to the Ministry of Culture and it is the Ministry that makes the final decisions and assumes full responsibility for them. This is a very conventional way of working in the Civil Service.
331It is true that today the committee calls on the services of the Ministry of Culture and of scientists and experts. It seems to me that this was necessary, because when it was set up, it was a matter of urgency and very important decisions had to be made in a relatively short time.
332For the future, as announced by Ms. Albanel, we will make this committee even more independent and broaden recruitment to the international level. It will be able to hold effective discussions with the Ministry of Culture. Of course, the Ministry expects us not only to pursue but also increase this interdisciplinary research. It is absolutely essential for Lascaux, as it is for many caves around the world.
333Earlier on, Philippe Malaurent indirectly raised the issue of resources. I would like to state that, for the Ministry of Culture, there are no budgetary problems as far as Lascaux is concerned. This is a national and global issue, and the Ministry will of course provide the resources required for the development of research. This is not new, but I would like to confirm to the researchers and managers that the State, fully aware of its responsibility, is not economizing on the financial resources for Lascaux.
334Mr. Max Schvoerer
335I can only say I am delighted, as a researcher, to hear such a proposition being made by the Ministry. I would like to make two remarks.
336The first is addressed to Jean-Michel Geneste. I do not think that the only thing that counts is the power of the lamps used. The wavelength, that is to say the energy transmitted by each photon, is also of importance. It is possible to have very little power and high-energy photons. You must therefore be on your guard concerning that.
337More generally speaking, I would say that, as an old professor, I less and less often attend conferences and symposia where they present ready-wrapped packets of finished work. Here we are facing an emergency. Though this term may come from the medical world, it has been justifiably used in this case. This morning another word was also used, that of humility, and I think that is extremely important.
338I am delighted with the idea of creating a laboratory but it should be a new, modern laboratory. The focal point would be, for example, in France, but it should also have exterior points, with a scientific community of representatives from other countries who are interested in this subject and working with us. That would be a move in the direction that the European Commission and its General Research Directorate would like to take. I applaud this idea, but we must act quickly.
339Mr. Gaël de Guichen
340Forty years ago, after eighteen months spent in place as an engineer in charge of the conservation of the cave, I regretted leaving this responsibility. I thus attended the committees presided at the time by Mr. Ségogne and would like to clarify, since the problem has been raised, the decision making process at the time. First of all, there were only ten people around the table. The members of the committee had a profound knowledge of the cave: the meetings took place in the building locacted 100 m from the entrance, and not in offices in Bordeaux. There were two sub-groups, one for the biological problems and the other for the physic-chemical and geological problems. The protocols of intervention were decided upon with the agreement of the two subgroups. The president did not allow anything to happen if the biological group had not given its approval since it was the microorganisms that had raised red flags. If only one point needed to be clarified or one observation verified, we went into the cave. Once a decision was made, it was executed by a team composed of an engineer, a technician and one of the discoverers of the cave, Jacques Marsal, whose major role has not been sufficiently recognized here. This team was in place day and night, seven days a week. It had the knowledge and competence to react and respond to any situation by immediately executing the instructions given by the committee. I was the last of the engineers in place. It is very unfortunate that for administrative reasons such a team was not recreated and put into place when the problems arose in 2000. We cannot take care of Lascaux from a distance.
341Finally the preceding committee and this team workrd in a less stressful manner, but times have changed and the exterior pressures are different.
342Mr. José Delgado Rodrigues
343Thank you.
344Ms. Laurence Léauté-Beasley
345I would like to ask Jean-Michel Geneste about the lighting regarding his abandoning the very rigorous preservation protocol requiring that there should be no more than 35 minutes of human presence and lighting, five people a day and five days a week. This protocol was in existence for a long time and scrupulously complied with. The importance of light in the cave is therefore a factor in the microbiological and physicochemical levels that he knew well. How did he makes the transition to go from this very rigorous protocol to abandoning it during the period of the state survey, with much longer periods of human presence in the cave and much more intense lighting? How did he changes from one protocol to the other?
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