In my blogpost Planning a period scribal kit, part 2 you can read about my plans on making a penner case using the cuir bouilli technique. In this post I will write about how I did and what I learned.
About cuir boilli
When starting this project I did not know much on cuir bouilli and how was made. I do not own any books about leather so I turned to Google, a very good friend of mine.
I found a conference paper written by Lieve Watteeuw & Marina von Bos. : A 15th-century Flemish enclosed garden in cuir bouilli. Production, degradation and conservation issues of a small painting on leather
Following text is from their paper:
“The technique of cuir bouilli or boiled leather was popular in Italy, Germany, Paris and Flanders in the High Middle Ages, not only for cup, bottle and relic cases, armour (including parade shields), bookbindings and bookboxes, but also for covering and decorating small, highly sophisticated coffers with chivalric love scenes and other subjects.2 Paris and Flanders were known for the production and export of these luxury goods through trade routes that reached across Europe (Didier 1978, Cherry 1982). Cuir bouilli objects were produced by specialist leather workers, associated with the guild of the cordoeaniers (Middle Dutch term derived from the French word cordouanier), and needed skilful craftsmanship.”
…..
“Cuir bouilli is a process used to change flexible, vegetable-tanned leather into rigid, moulded and often intricately shaped objects (Davies 2006). For shaping of the vegetable-tanned leather, heat and moisture were used, as indicated by the term ‘boiled leather’. No written medieval sources describing the production of decorated cuir bouilli objects survive, so knowledge of the process relies on the important studies of the Scottish leather historian John William Waterer (Waterer 1981 and 1986). More recently, Davies and Payton (2001) described at least three different ways to make cuir bouilli. Experimental reconstructions of cuir bouilli objects, using different recipes, by a group of leather conservators and craftsmen (Neno et al. 1995, Carlson 2003), found that the leather used would be half or fully tanned and that, in response to different requirements, a large range of methods, materials and techniques could be used in varying combinations”
I also found a blogpost written in french by Anne Deré about one way to do cuir bouilli with gelatine as glue. Unfortunately french is not a language I understand and the translation was a bit tricky to read. Even if Anne´s blog is written in french and the translation could be better she writes more interesting have posts about cuir bouilli, like one where she experiments with different heat- and time-exposure and how leather soaked in water behave compared to leather soaked in gelatine.
Keeped on searching and found this pdf: Cuir Bouilli Technique –An Historical Method of Hardening Leather that is written by Jean Turner. The pdf contains very good information about the term cuir bouilli, some different techniques and a english translation of Anne´s blogpost. I really recommend reading it all if you want to try this or know more about it.
In both Turners pdf and Watteeuw & von Bos;s paper one can read about the lack of medieval sources of the technique of cuir bouilli. I however wonder if Cennini actually describes some kind of this technic in his book. More about this at the end of this blogpost!
Making the penner case
I choose to use a case from the Metropolitian museum as inspiration. This case have two interior compartments designed to contain a knife and spoon. Mine is going to hold my quill pens and my brushes. I also choosed to use Anne´s method with soaking leather in gelatine water and make a seamless penner! I started the process with choping and carving out two wood cores from a log.
After this I cut out some leather pieces that was a bit to big for the wood cores since I had read that the soaking and heating would shrink the leather.
I almost followed Anne´s gelatine method. However I did not put the gelatin and water in a jar or waited for a couple of hours. Instead I put it all in a small casarole and heated it up since I know that gelatine dissolves quickly when heated. The fluid was heated to around 37C, I actually heated the fluid to a higher temperature later and it still seemed to work without damaging the leather!
Here is a video from my instagram from when a piece of leather is put down into the fluid. One can see how it bubbles and that this might have been why it was called cuir bouilli, even if the fluid is not infact boiling. After being soaked in the heated fluid for about 10 minutes I shaped the pieces around the wood cores, pressing, shaping, cutting and forming the leather after the form while I was working. If the cores have had a even shape one could probably cut out a pattern fitting the cores better from the beginning. Each layer of leather was dryed in the oven meanwhile I worked on the other form.
On this pictures you can see how the leather have joints were the leather have been fitted edge to edge.
While making new layers I made sure that the joints did not end up on the same place as the layer done before. Hoping that this would prevent the case from split up because of the lack of seams. I did two thin layers on each form so that my case would have two interior compartments. If you look at the pictures below, the left one and the middle one shows the first layer on both forms and the joints. The picture on the right shows the second layer and how the leather pieces is formed. Note that the joints is on the opposite side from the first layer.
After the two thin layers I put the cores together and with a thicker leather I formed a third layer around them both, joining them to one piece. The edges on the thicker leather did not close very good at the bottom and top of the cores. Which made me worry about the case breaking in does spots. So I decided to do some piecing and glued on small leather pieces to hold the edges in place. Insicions was cut through the third layer. These insicions was lifted and then hold in place by some grill sticks until the final drying of the leather.
After this a fourth and final layer made from the thin leather was added. The grill sticks was removed for a while when laying down the fourth layer that also got the insicions.This is how it looked when all layers were in place:
Tooling the leather
After talking to Lia I decided to write household de Thornegge´s motto on it: Secundus semper melius, that means: the second is always better refering to the second try when crafting. I also decided to add my coat of arms and acanthus leafes since both those motifes can be found on various coui bouilli finds from the 15th and 16th century.
I used a bonefolder when tooling the case. One can also use modeling tools and styluses made for this purpose ( I could not find mine), or use shape punches. Inspired by the pattern on the original piece I draw the pattern on freehand and decide how part by part would look while working on the case. When tooling leather this way I do not cut anything. I only put pressure to the leather with the bonefolder (or any other tool).
Below is some pictures of the process from making some acanthus leafes showing the first drawing in the surface to the finished relief acanthus pattern.
Taking out the wood core
This was the really scary phase, not knowing if it would work taking out the wood cores from the case. Started to cut a opening in the leather, then gently sawed apart the wood cores trying not to damage the leather. With exellent help from my partner, some patience, hard work and a lot of poking with screwdrivers and kitchen knives between the leather and the wood cores the wood cores finally came loose. It took about three hours!
After this I cut another piece of leather out to be used as a lining for the cap to keep it in place. Soaked the piece in gelatine water and glued it on the inside of the big pocket in the case.
Dyeing the case
Since I used period methods and techniques so far I did not want to use a modern alcoholic based leather dye to dye my case with. I started to read about dyeing leather and I found Guthrie Stewarts blogpost about dyeing lether black. When reading this blogpost I realized that that the described process of making the black dye was very similar to how I made my iron gall ink! The only thing missing was that my ink probably have a Ph to low to use on the leather. Guthrie however mention Ian´s page and how he suggest eggshells to neutalise the the acid. I have burned and grinded eggshells at home that I prepared last years for making and binding pigments on. So I went to Ian´s page and read about Oak gall ink – a more in depth look.
After reading this I simply put some of my iron gall ink and eggshells into a soup plate and tryed to dye leather with it. I also dyed a piece of leather with the iron gall ink without eggshells in it. The piece with eggshells in it turned out softer with the same feel to it that it had before dyeing. The one without eggshells became a bit more stiffer. But since the one with eggshell did not change the structure of the leather I decided to use the iron gall ink with eggshells to dye the leather with.
The case needed to be brushed with some layers of ink before it started to sink through the surface. After some coats and when the ink started to react with the leather the case turned into a nice black colour. When it was try I oiled it in and made a finger loop braid cord to the case.
Here is the finished case:
Did Cennini use cuir bouilli?
In the beginning of this post I talk about if Cennini actually describes some kind of cuir bouilli method in his book. This is what got me thinking that:
I just bought a swedish translation made by Karin Forsberg and Bo Ossian: Cennino Cennini, Boken om målarkonsten, Il libro dell`arte. According to Forsberg and Lindberg the translations of Cenninis book can be found in 4 different copies one made in 1437, one written in the end of the 16th century and two from the 18th century and there probably have been many more copies.
There are many questions about the copies since they all have some diffrens from each other. The copy that seems to be most in order is the one from the 16th century. The one from 1437 containing disordered chapters and texts and seems to be written by different hands. It even seems like some parts or words in the text have been skipped or not understod and some words or parts might even have been left out when being copied. Cennino Cennini, Boken om målarkonsten, Il libro dell`arte, Forsberg, K & Lindberg, B. p. 15-38.
In The craftman´s handbook, Il libro dell`arte Cennini writes about making model crests or helmets with leather and I wonder if it might have given the same result as cuir bouilli with gelatine:
How to Model Crests or Helmets
Whenever you have occasion to make a crest or helmet for a tourney, or for rulers who have to march in state, you must first get some white leather which is not dressed except with myrtle or ciefalonia, stretch it, and draw your crest the way you want it made. And draw two of them, and sew them together; but leave it open enough on one side so that you can put sand into it; and press it with a little stick until it is all quite full. When you have done this, put it in the sun for several days. When it is quite dry, take the sand out of it . Then take some of the regular size for gessoing, and size it two or three times.”Cennini, Cennino d’Andrea. The craftsman´s handbook, Il libro dell’ Arte. Translated by Daniel V, Thompson, p. 108-109
White leather meaned tanned leather and Thompson writes in his translation that ciefalonia could not be identified with certainty (p. 108). While Lindberg and Forsberg writes in their translation about “Valloner”, fruit bowls made of oak and that the leather would have been damped our wet to be able to stretch and fill with sand ( p. 156). Both myrtle and the bowls made of oak had a high contain of tannin and was used for tanning leather.
The leather was stretched and drawed on, then cut and sewn together before it was filled with sand and put in the sun to dry. He does not say anything about soaking the leather in water but when reading this and knowing the things about the copies that been used when doing the translations I start to wonder if Cennini, or the writer that copied the manuscript might have left out the soaking part of the leather since he recommend to put the leather in the sun until it is quite dry. I draw the conclusion that the leather somehow was wet since it need to dry. It might have been cuir bouilli
How Goat Glue is Made, and How it is Tempered; And How many Purposes it will Serve. Chapter CVIIII
And there is a glue which is known as leaf glue; this is made out of clippings of goats’ muzzles, feet, sinews, and many clippings of skins. This glue is made in March or January, during those strong frosts or winds; and it is boiled with clear water until it is reduced to less than a half. Then put it into certain flat dishes, like jelly molds or basins, straining it thoroughly. Let it stand overnight. Then, in the morning, cut it with a knife into slices like bread; put it on a mat to dry in the wind, out of the sunlight; and an ideal glue will result. This glue is used by painters, by saddlers, and by ever so many masters, as I shall show you later on. And it is a good glue for wood, and for many things. We shall discuss it thoroughly, showing what it may be used for, and how, for gessos, for tempering colors, making lutes, tarsias, fastening pieces of wood and foliage ornament together, tempering gessos, doing raised gessos; and it is good for many things.Cennini, Cennino d’Andrea. The craftsman´s handbook, Il libro dell’ Arte. Translated by Daniel V, Thompson, p.67
Since it was a struggle getting the wood cores out it seems like filling the leather with sand would be a good idea. When the leather have dried it should just be to cut it open and pour out the sand. I will try my thesis and see if it works.
Reference:
Cennino Cennini. Boken om målarkonsten, Il libro dell`arte, Karin Forsberg och Bo Ossian Lindberg, Lund, Sekel bokförlag och författare, 2011
Cennini, Cennino d’Andrea. The craftsman´s handbook, Il libro dell’ Arte. Translated by Daniel V. Thompson New York: Dover, Publications Inc, 1933, 1960
Conference paper written by Lieve Watteeuw & Marina von Bos
https://www.researchgate.net/publication/285833635_A_15th-century_Flemish_enclosed_garden_in_cuir_bouilli_Production_degradation_and_conservation_issues_of_a_small_painting_on_leather
Anne Derès blogpost
http://astelier-medieval-du-cuir.over-blog.com/article-21921258.html
Jean Turners pdf
https://www.jeanturner.co.uk/static-content/tutorials/CuirBouilliTechnique.pdf
Guthrie Stewarts blogpost
https://distillatio.wordpress.com/2012/11/29/dyeing-leather-black-a-bit-like-alchemy/
Ian the Greens homepage
https://sites.google.com/site/ianthegreen01/ian’sinkmakingpage/oak-gall-ink-2
Museums
https://www.metmuseum.org/art/collection/search/468350?=&imgno=10&tabname=label
Silwa goes purjo 
[…] it with. If you want to read more about how to do cuir bouilli then please visit my previous post: Cuir bouilli penner case. I did not take so many pictures when making the ink pot but here´s […]