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L'alun de Méditerranée

 | 
Philippe Borgard
, 
Jean-Pierre Brun
, 
Maurice Picon

The use of Alum in the preparation of tawed skin for book covers in the 11th – 15th centuries: advantages and disadvantages for the book structure

Cheryl Porter

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  • 1 The blind tooled Romanesque bookbindings on (tanned) leather, made mainly in France and England we (...)

1From the 11th century to the late 15th century, alum tawed skin-plain white or brightly coloured-was the preferred covering material for books. Though vegetable tanned leather was also used for book bindings from before the 11th century, its use was rare until the 16th century1 There are a number of very good reasons why, for more than four hundred years, the use of tawed skin predominated. In order to understand the advantages of the using these skins, it would be helpful to examine the way they were made and note how they differed from vegetable tanned skins.

  • 2 In ancient times the production of tawed skin was an acid process. It is suggested that this was d (...)
  • 3 See various recipes and illustrations in e. g. J. de Fontenelle and T. Malepeare, Philadelphia, 18 (...)

2The basic technology for tanning and tawing skin changed very little from Greco-Roman times until the late 18th century2. There are a number of recipes for tawing skin with alum (see Claire Chahine s article). Most recipes used a variation on a number of ingredients including lime for de-hairing, “drenching” in bran and water, and then tawing with a paste of alum, common salt, flour, eggs, butter and oil. After the final process of “staking” to further soften the skin and make it more flexible, it could be coloured, if so desired. Vegetable tanned skins were begun in the same way, with de-fleshing and washing, vatting in lime and drenching in bran and water, before being put into (oak bark) tanning pits3.

3The tawing process was quite fast-about one week for the pre-tawing, and one to two days for the actual alum process – and the finished skin could be soft and flexible enough to be used for gloves, and/or strong enough for pouches and purses. In fact, it was so strong, supple and durable that the armourers in medieval times were directed to use it for lacing plate armour together. (It had to be positioned behind the plating so as to avoid getting wet).

  • 4 This applied also to the tanned skin workers, who were obliged to be « down stream and down wind »
  • 5 The use of volcanic alum was specifically forbidden because it contained iron impurities, which af (...)

4In Venice, tawyers had their own gild with their own statutes from the early 13th century. Not only were they obliged to manufacture their skins outside of the town, since the pre-tawing bath was considered to be too evil-smelling4, but the finished product had to be accompanied by both a statement of the quality of the skin and of the nature of the alum used for its production. The use of volcano alum was specifically forbidden5.

Fig. 1-“Tawyer 1473”, from Das Hausbuch der Mendelschen Zolf Bruderstiftung zu Niirnberg, Munich, 1965.

  • 6 Singer, op. cit., p. 120-121.

5There were also special and specific regulations for the tawyer in Germany, France and England. In Germany, the « white alumed leather » was very fine and very costly and always clearly distinguished from cheaper products vegetable tanned in the normal way6.

  • 7 From the 15th century sumac-tanned Nigerian goat skins (earlier in the Arab world) was also used t (...)

6Tawed skins used for book covers have generally survived longer and in better condition than historic books bound with tanned skins. One reason for this is that tanned skins have a tendency to rot, because they rely upon tannins (often from oak bark in Northern Europe or sumac, in the Mediterranean) which have a tendency to react with acidic materials (pollution, for example). Alum, however, is a preservative that inhibits loss of strength and prevents putrification and rotting... unless it gets wet. Luckily, this is a relatively uncommon fate for books, but for shoes and saddles and other objects that need to withstand wet conditions, alum tawed skin is completely unsuitable and vegetable tanned leather must be used instead7.

  • 8 Though little work has been done on the use of tawed skin as a binding material on Continental bin (...)

7There was a traditional rivalry between the alum tawyers and the leather tanners. The tanners felt both their craftsmanship and the skins they produced to be far superior to those of the tawyer. Vegetable tanned leather was made from the finest skins – calf and sheep especially, whereas the whittawyer was known to use a variety of low-cost skins, including sheep, goat, deer, horse, dogs, squirrel, rodents and animals found dead. There are even records of the use of chicken skin. What we know from the examination of book covers is that the most commonly used tawed skins in Britain were from calf and sheep. In the Germanic world (including the Low Countries) pig was probably the norm, and goat or sheep skins most commonly used in the Southern European/Mediterranean regions. This was a reflection of the local agricultural practices8.

  • 9 See Nicholas Hadgraft and Michael Gullick article in Cam- bridgbridge History of the Book, vol. 11 (...)

8There are many who consider that around the 11th century, bookbinding in Northern Europe reached a high point, which it has never since been equalled. This may come as a shock to those of us who are familiar with (for example) the achievements of the fine tooling and gilding of later centuries, but those who hold with the 11th century, are concerned most especially with the structure of the book. As much as in the craftsmanship, the argument concerns the quality of the materials used in the construction of the 11th century book. Whereas it might be possible to replicate such a structure in vegetable tanned leather, it would certainly not have withstood the test of time in the way that the Romanesque examples have9. The Romanesque period marks the beginning of the great age of tawed skin. From this time, until the end of the 15th century, the use of alum tawed skin was the predominant book covering material.

Fig. 2-a : “Peter Lederer, 1425”, from Das Hausbuch der Mendelschen Zolf Bruderstiftung zu Nürnberg, Munich, 1965; b: “The Whittawyer”, from Eygentliche Beschreibung aller Stande auff Erden... durch Hans Sachsen beschrieben, vnd in Teutsche Reimen gefasset vnd auch mit kunstreichen Figuren in Druck verfertigt. Franckfurt am Mayn, 1568.

  • 10 From studies of English books of the period it seems that these tawed skin chemises were used for (...)

9Until the 12th century, most books were made in monasteries for monks. In the 13th century, the making of books became increasingly secular and urban-based, in response to a new market. Though the great majority of the population remained illiterate, the increase in literacy, due to better education and the growth of universities, meant that many more books were needed by the laity. However, though we now see the beginnings of private libraries and a profitable book trade, it should not be supposed that the primary business of the tawyer was supplying skins for covering books. On the contrary, this would have constituted only a small part of the trade, compared with, for example, glove making and other items of clothing. It is interesting to note too, that, from this time, coloured alum tawed skins were increasingly used for bookbindings. Again, though little work has been done on this aspect of book history, when we look at contemporary pictures of books and their covers, (especially in the 14th and 15th centuries) they are almost always depicted as having been coloured. In manuscript paintings, wall and easel paintings from Iceland to Spain, from England to Italy, Czech, Germany and France, we see these alum tawed skins in reds, greens, yellows, blues, blacks (and white). Sometimes they have brightly – coloured chemises wrapped around them to exclude the dirt and dust from the leaves10. Even more frequently, what we see depicted in these pictures, are the coloured tawed skin primary covers themselves.

  • 11 Medieval books were stored in furniture designed to hold books horizontally. See Henry Petroski, T (...)
  • 12 On the whole, tawed skins of the 11th century were much thicker than in the following centuries. F (...)

10It is strange therefore, that when we look for evidence of coloured alum tawed skins in historic collections, it is not easy to find. There are a number of reasons why this is so. It is sad fact that comparatively few books from this time have retained their original bindings. The study of book structures is a relatively new concept and book bindings were (and very often still are) considered of little value or interest compared to the text or the painting contained within the covers. By the end of the 16th century, with the advent of the modern bookshelf, heavy chemise book covers were discarded completely, or at least partially, with the skirt cut off and truncated, in order that the book could be stored vertically on the bookshelf, instead of in the medieval tradition of horizontal book storage11. Although many books do survive with only the primary cover, many more were lost for, once the protective chemise was removed, the book was far more vulnerable. This is because the primary cover tended to be rather thin12 and when no longer protected by the sturdy chemise, it was easily damaged. Without its original protection and support, the books remaining structure was at risk and the wear and tear and breakdown from handling would be more apparent, so that re-covering (doubtless in the latest fashion) would be an attractive option.

  • 13 Gold doesn’t show up well on cream-coloured skin (the same problem as with parchment).

11Later, with the invention of the printing press, the sheer numbers of books requiring storage was simply overwhelming, Very frequently too ; original bindings were discarded to meet the demands of contemporary fashion. From the 16th century, vegetable tanned leather – heavily and expensively tooled with gold – was considered far superior to plain or coloured tawed skin13. Yet another problem encountered when trying to identify these books is that even when they are in their original bindings, they are often so discoloured and dirty, that they appear to be tanned leather, rather than tawed skin. Not surprisingly, there is even less evidence of the use of colour on tawed bindings. Unlike textiles, tawed skin does not have the fibres that retain evidence of past colour. Furthermore, the method of applying the colour was a surface-only method, and after hundreds of years of use, the surface is often so abraded, and/or with such heavy accretions, that no colour can be detected. Mostly, the only evidence of the original colouring can only be seen in those areas protected both from handling and from light: areas such as the turnins and under the paste-downs, where the parchment or paper has lifted of its own accord (since neither parchment nor paper always sticks well to tawed skin).

  • 14 I am indebted to Michael Gullick for this information, which is based on his personal observations (...)
  • 15 See survey of 15th century bookbindings in Nicholas Hadgraft PhD Thesis, The Fifteenth Century Eng (...)

12The study of English book covers suggests that coloured covers in the 12th century would have been extremely rare, if they existed at all. From the 13th century the colour red seems to have been the most common, and black and green are also mentioned in inventories of this time14. Colour was used increasingly throughout the 13th and the 14th centuries, and by the 15th century, probably at least half of all tawed skin bindings were coloured15.

  • 16 Cheryl Porter, The colouring of alum-tawed skins on Late Medieval books, Dyes in History and Archa (...)
  • 17 The Plictho of Gioanventura Rosetti, Venice, 1548. Translation by Sydney M. Edelstein and Hector C (...)
  • 18 There is evidence on the 15th century Pembroke manuscripts (from the Medieval Priory of Bury St Ed (...)

13During the course of this research I have examined many manuscripts with evidence of colour on their tawed skin bindings16. In every case but one, the colour had been applied on one side only, the verso remaining white. The skin which had colour on both sides had two different colours (of the 15th century and possibly indicating re-use of the skin). Obviously therefore, the colour was not applied in a dye bath, nor in a vat. To do this, the whole skin must be immersed, and the colour would be evident on both sides of the skin. In all of the examples studied, the colour had been painted onto one side only of the skin (there seemed to be no discernable preference for flesh or hair side), using a brush or another implement. This is completely in keeping with the recipes that we have for colouring skins – parchment or alum tawed – from medieval and renaissance times17. In fact, applying colour to alum tawed skin is very simple18. The colour is extracted from the organic substance (usually by soaking the plant/animal matter in hot water) and then painted directly onto the surface of the tawed skin. The alum in the skin quickly forms a bond with the colouring matter and fixes the colouring matter onto the skin. (The alum acts as a mordant and an insoluble lake is formed). The colour is often brighter and more intense as a result of this bonding. For colouring with vat dyes, such as indigo, the colour was painted on as a pigment with some sort of binder (gum Arabic or protein “glue”) to stick the particles to the skin.

14Our analysis of colour on tawed skins has shown that many of the assumptions about the nature of these colours used for book bindings in this period are wrong. For example, it was often assumed that the prestigious and expensive books with red tawed skin covers would be coloured with the most expensive and prestigious red colour kermes... but not at all. By far the most common red was found to be brazilwood – a substance so lacking in light fast quality, and so cheap, that it was not used for precious textiles or for grand panel paintings, but instead for shop signs and other minor, non-prestigious projects.

15In the late 15th century, with the invention of printing with moveable type, the demand for books increased enormously. The printing press made books more available and more affordable (though again, it should not be assumed that there was anything approaching universal literacy, nor that any but relatively wealthy elite had the ability to pay for books). However, one result of the greater demand for books was a huge increase in the use of vegetable tanned skins, and a gradual diminishing of the use of tawed skins for bookbinding. The tawyers simply could not meet the increasing demand for covering materials. It was the tanners who were able to satisfy the new market demands, since they were already firmly established in most towns, supplying other trades such as the shoe and saddle makers, and who were therefore, very well-positioned (and incidentally, more numerous and better organised) to meet the increased demand – in a way that the poorly organised, one-man production tawyers could not. (It would be interesting to know if the alum famine in Western Europe at this time was another factor in the tawyers’virtual withdrawal from the book market).

  • 19 In the last decades of the 15th century, print runs increased in the average size of editions from (...)

16Perhaps another factor working against the tawyer was that the production of books in the age of printing was focused in Oxford, Cambridge and London, in England, and similarly in large cities on the Continent. Although centres of printing are not always centres for binding (which tend to be much more widely dispersed than printing centres), large cities tended to be the domain of the tanner, who was geared for production of large quantities of leather for saddles, shoes and so on. Hitherto, manuscript production was locally based, as was the tawyer, who traditionally provided skins for locally-produced books. The massive production of the city-based printing presses19 was simply unable to be serviced using the existing methods and technology of the tawyer.

  • 20 The great exception to this rule is the use of tawed pigskin in the Germanic world, which predomin (...)

17Though the tawing of skin did continue, for gloves especially, and even for some books – notably in the Germanic areas – by and large, the invention of printing with moveable type in the 1460’s, saw the end of large-scale production of alum tawed skins for book binding20. There are exceptions to this general decline and they are about the ability to achieve bright colours with tawed skin. In the 16th and first half of the 17th century large numbers of French books were covered in reversed, stained alum-tawed goat and sheep. Tawed skins were also used in England when bright colours were required, and for almanacs.

  • 21 They are not entirely compatible because the acid in the alum can react to the vegetable tanned le (...)
  • 22 In the 16th and 17th centuries England and France, thin tawed skin – red, black, purple, brown and (...)

18In some cases a combination of vegetable tanned leather and tawed skin was used – one material complimenting the other. Thus, one might find a vegetable tanned hide cover with tawed edge piping, or in other cases, a tawed chemise with tanned edge piping. Chemically, the two materials are not really compatible and new skins are advisedly stored separately, but in historic examples, it works well enough21. In the 16th and 17th centuries, it is not unusual to find the two materials wound together and used as sewing supports. It has been suggested that in the post-medieval period this probably signifies that scraps from other trades may have been used22. In the medieval period however, it is clear that book binding vegetable tanned leather and alum tawed skins were purpose – selected and purpose-made. Both tawed skins and leathers were highly prized and expensive and thus we find damaged skins which have been “pieced” together with beautifully-sewn original repairs, made prior to their use for covering.

19Towards the end of the 15th century, the techniques of the bookbinder modified and abbreviated, in order to be able to work at a faster pace for increased production – to bind more books in less time. Such measures, however, did not reduce the cost of a binding. The economics of the trade demanded both increased production and reduced costs and this could only be achieved by using cheaper materials as well as speeding up production. What was inevitable was that both the quality of the craftsmanship and the quality of the materials used would decline as a direct result of these market forces.

Notes

1 The blind tooled Romanesque bookbindings on (tanned) leather, made mainly in France and England were produced until about 1225. The style did not re-appear until towards end of 15th century.

2 In ancient times the production of tawed skin was an acid process. It is suggested that this was discovered in Egypt, where the women removed hair from their limbs by applying damp oatmeal and then exposed them to the sun. This same acid process was used to rot and de-hair animal skins. Probably, before the medieval period, this changed to the alkali process. The results were the same, though (it is claimed) the odours produced were not so outrageous.

3 See various recipes and illustrations in e. g. J. de Fontenelle and T. Malepeare, Philadelphia, 1852 and Das Hausbuch der Mendelshen Zolf Bruderstiftung zu Nurnberg, Munchen, 1965. Alum was not sent to England before the Conquest. It is first mentioned in the Libertas Civitatum of about 1200. See Charles Singer, The Earliest Chemical Industry, London, The Folio Society, 1948. Any tawed skin book covers on English books before this time must therefore have imported the skins already tawed. The tanning of vegetable tanned skins was said to take «a year and a day».

4 This applied also to the tanned skin workers, who were obliged to be « down stream and down wind ».

5 The use of volcanic alum was specifically forbidden because it contained iron impurities, which affected the colour and interfered with the dyeing process, and in great amounts, caused skins to crack.

6 Singer, op. cit., p. 120-121.

7 From the 15th century sumac-tanned Nigerian goat skins (earlier in the Arab world) was also used to bind books in Europe and for most purposes, especially resistance to light damage, this is as good as tawed skin.

8 Though little work has been done on the use of tawed skin as a binding material on Continental bindings before the 16th century, we suppose that the animal species used were most likely those used for parchment.

9 See Nicholas Hadgraft and Michael Gullick article in Cam- bridgbridge History of the Book, vol. 111, Cambridge University Press (forthcoming) and note the analogy of the 11th century book... Built like a Norman castle – immense, strong, heavy, robust, rugged, long-lasting, with sewing supports more than a centimetre wide and 8 mils thick. Compared to (for example) a Grollier (French 16th binding)... made like a lady’s purse – slight, beautiful.

10 From studies of English books of the period it seems that these tawed skin chemises were used for library books as well as for devotional/church books. From the late 14th century (at least) these over-covers were often made from coloured textiles. See Anthony Hobson’s introduction to Frederick A. Bearman, Nati H. Krivatsky and J. Franklin Mowery, Fine and historic bookbindings in the Folger Shakespeare Library, 1992. One sometimes sees depictions of silk or velvet over-covers on private devotional books from 14th –16th century Flemish paintings.

11 Medieval books were stored in furniture designed to hold books horizontally. See Henry Petroski, The book on the bookshelf, Alfred A. Knopf, New York, 1999.

12 On the whole, tawed skins of the 11th century were much thicker than in the following centuries. From the 12th to the 15th century, skins used for primary covers were progressively thinner.

13 Gold doesn’t show up well on cream-coloured skin (the same problem as with parchment).

14 I am indebted to Michael Gullick for this information, which is based on his personal observations of English manuscript bindings as well as his research on literary evidence.

15 See survey of 15th century bookbindings in Nicholas Hadgraft PhD Thesis, The Fifteenth Century English book structure. University of London, 1994.

16 Cheryl Porter, The colouring of alum-tawed skins on Late Medieval books, Dyes in History and Archaeology, 16/17, 1997-1998, p. 119-203.

17 The Plictho of Gioanventura Rosetti, Venice, 1548. Translation by Sydney M. Edelstein and Hector C. Borghetti, The MIT Press, 1969.

18 There is evidence on the 15th century Pembroke manuscripts (from the Medieval Priory of Bury St Edmunds) that the colour was applied after the book was covered, as the stain appears on the wooden boards as well as the skin. In all probability, the colour was applied by the binder.

19 In the last decades of the 15th century, print runs increased in the average size of editions from 200-300 to 400-500 and reaching 1000-1500 in the early 16th century. There was also a corresponding drop in the cost per volume. See Nicholas Pickwoad, Onward and downward : how binders coped with the printing press before 1800, in : A Millennium of the Book. Production, design and illustration in manuscript and print 900-1900, Robin Meyers and Michael Harris (Editors), New Castle, Delaware, Oak Knoll Press, 1994, p. 63.

20 The great exception to this rule is the use of tawed pigskin in the Germanic world, which predominated throughout the 16th century. It should be noted also, that very little is known about bookbinding at this time in the Iberian Peninsular, and it may be that tawed skins continued to be used here for longer.

21 They are not entirely compatible because the acid in the alum can react to the vegetable tanned leather and cause rotting.

22 In the 16th and 17th centuries England and France, thin tawed skin – red, black, purple, brown and yellow – were frequently used as sewing supports. These skins are coloured on the fleshside. See Nicholas Pickwoad, op. cit, p. 79. It is clear that this is not a response to what was considered fashionable by the book trade-as in earlier centuries. The skins available for sewing supports were those pre-dyed for other purposes, and these otherwise unusable scraps were then passed on to the book trade as required.

Table des illustrations

Légende Fig. 1-“Tawyer 1473”, from Das Hausbuch der Mendelschen Zolf Bruderstiftung zu Niirnberg, Munich, 1965.
URL http://books.openedition.org/pcjb/docannexe/image/608/img-1.jpg
Fichier image/jpeg, 775k
Légende Fig. 2-a : “Peter Lederer, 1425”, from Das Hausbuch der Mendelschen Zolf Bruderstiftung zu Nürnberg, Munich, 1965; b: “The Whittawyer”, from Eygentliche Beschreibung aller Stande auff Erden... durch Hans Sachsen beschrieben, vnd in Teutsche Reimen gefasset vnd auch mit kunstreichen Figuren in Druck verfertigt. Franckfurt am Mayn, 1568.
URL http://books.openedition.org/pcjb/docannexe/image/608/img-2.jpg
Fichier image/jpeg, 439k

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