This page was created by Marc Carlson
It was last edited 9 June 2004
Just a few words on this, if I may. This document is not intended as "the last word". To be blunt, I don't think at this time that there can be a last word on what "Cuir Bouilli" is or was. The term may have undergone change changed in meaning depending on when and where it was used. What this started out as was a compilation of a discussion by several people back in 1996, just shooting the breeze, sharing sources and experimental information. This has been expanded by more information uncovered by other people since then. If you have information that's not in here, please feel free to let me know. Yes, the name up there is mine, since I'm the guy bringing this all together - but it's not just me speaking here. If you contribute, you will be acknowledged.
Cuir-bouilli (From the Oxford English Dictionary, 2d
Ed.) Forms: 4/5 quir-, quyr- boilly, -boily, -boyly, -boile,
-boyl(l)e, quere- boly, qwyrbolle, coerbuille, -boyle, 6 Sc.
cur-, corbule. [F., lit."boiled leather."]
Leather boiled or soaked in hot water, and, when soft, moulded or pressed into any required form; on becoming dry and hard it retains the form given to it, and offers considerable resistance to cuts, blows, etc.
The word was in common English use from 14th to 16th c., after which it is not found till modern times, when it appears as borrowed from modern French.
1375 Barbour Bruce xii. 22 On his basnet hye he bar Ane hat off qwyrbolle.
1386 Chaucer Sir Thopas 164 Hise Iambeux were of quyrboilly [v.r. quereboly].
1400 Mandeville (Roxb.) xxvi. 123 ai hafe platez made of coerbuille.
1413 Lydg. Pilgr. Sowle iv. xxx. (1483) 80 A feyned hede formed of playstred clothe other of coerboyle.
1513 Douglas ?neis v. vii. 77 Thair harnes thaim semyt for to be Of curbule corvyne sevin gret oxin hydis.
1880 C. G. Leland Minor Arts i. 1 Solid or pressed work, known as cuir bouilli, in which leather after having been boiled and macerated, or rendered perfectly soft, is moulded, stamped, or otherwise worked into form.
Basically Cuir Bouilli is a means of making hardened and stiffened leather. Although there is some disagreement among some leatherworkers as to how this is accomplished, there is a significant amount of evidence to think that it was done by molding wet vegetable tanned leather. This leather can be formed into any number of forms, which, on drying, will retain that shape. The wet leather can be set more firmly by drying it under moderate heat, the degree of rigidity obtained being determined by the drying temperature. A faster method, which produces extremely hard and rigid shapes, is to dip the molded leather into boiling water for anywhere from 20 to 120 seconds. This technique causes the partial melting of the fixed tannin aggregates in the leather, making them plastic, causing them to flow and redistribute themselves throughout the fiber network of the leather. On cooling, the fibers become embedded in what can best be called a tough, three-dimensional, polymer network or resin, somewhat similar to the materials made by condensing formaldehyde with substances such as phenol, urea or melamine.
The molding of leather was known in Saxon times in England, and was widely practiced during the middle ages in both England and on the Continent.
There are a number of suggestions for how to do this, and none of the following discussions are any more authoritative than any of the others. Essentially, it seems to require the proper sort of leather, carefully applied heat, and possibly some form of liquid. The final answer, is for you to use the method that you think is more appropriate, based on your final goals.
There is a great deal of confusion about the term "cuir bouilli" in the literature about leather. Some sources seem to think that it was shaped/hardened with wax, others by wetting, shaping, and drying. The best sources seem to be R. Reed and Waterer (Leather Craftsmanship, Leather and the Warrior) who seem to agree that cuir boulli was formed by wetting and drying.
I would like to stress something that is often insufficiently stated, if stated at all, during the various descriptions of leatherwork in general, and in this case, specifically of the various ways to make Cuir Bouilli. Since we are dealing with an organic substance, and I refer to "organic" in more than its merely having once been alive, each piece is unique and will handle differently. Two otherwise similar bits of leather can react quite differently. What this means is that you can do everything described hereafter perfectly and still have your project fail, or at least come out with a finished product that is not up to what you had hoped. Don't be discouraged. Leather hardening is not always a "cut and dried" science when dealing with the levels of technology we are working with.
The first, and the easiest, is to soak the leather in cold water (as long as you want to, suggestions range from 15 minutes to 12 hours or longer) then form it and let it dry. This may not seem all that great, but if you've seen a vambrace after it's been sweated into after a summer, you know it can harden up quite a bit. If you tool the leather while it is wet, you will make it even harder.
Soaking leather to make it harder is really more appropriate for vegetable tanned leather.
Some people have suggested soaking the leather in lye or urine, but I have no idea if these actually work any differently than using normal water.
The hotter the water you soak it in, the harder it will be when it dries. However, each bit of leather has it's own point at which the water is TOO hot, and will be cooked by it. If this happens, your best bet is to keep it hot, and stretch it out on a form and let it dry. It becomes very hard and brittle, but that's the penalty for over ambition.
I tend to get it about as hot as I can stand to put my hand into, and maybe a trifle hotter, but as long as it doesn't burn me, I assume it shouldn't burn the leather.
Sue Hallock (Kendra of HollyOak)
If you decide that you want to place your leather into boiling water, and be warned that many people consider this a patently silly thing to do, you will want to be prepared to have your leather shrink and harden very quickly. I would advise actually placing the whole form you are working with and keeping it in the boiling water for not more than about 2 minutes. What this does is to cause chemicals in the leather to liquify and polymerize (see later discussion below) until it shrivels into plastic hardness.
I wish to specify this since I, at least, try to avoid having my heat treated leather shrivel up into a plastic mass because it's more difficult to manage.
Do not dip leather in to Boiling water - UNLESS you know what you are doing!.
If you take cold formed leather and while it is still on the form and pour REALLY hot water over it, letting it drain off (say fresh from a coffee maker), it will scald the surface of the leather and harden the outer layer without altering the inner layers at all. By the time the water's soaked the rest of the leather, it has been cooled (by having to heat the leather) sufficiently that the temperature's dropped back down to the 120-140F range.
You can also presoak the leather in water, then pour the boiling water on top. This either heats up the water inside the leather, so you don't have to wait for it to soak in, or the cooler water slows the soaking process, letting the outside of the leather harden more fully. I've tried it both ways and I couldn't tell you which worked better.
According to J.W. Waterer, Cuir Bouilli is made by soaking vegetable tanned leather in water until it is thoroughly water logged, then molding it to form and drying it in a constant temperature of 50C (or 122F).
Baking the wet leather can make it even harder, say in an oven, but you run the risk of steam scalding it and making it shrink (as per C, though see below).
Play with scrap pieces until you get the temperature about what you feel is just right, and then bake your pieces, tied to the forms with string, stitched, or nailed in place.
Reed goes into a bit of detail about the structural/chemical changes involved, and why it must be vegetable tanned leather. The key factor is the heating, and the presence of water may play a part. As far as I can remember, neither author mentions the use of wax or oil. Unfortunately, neither author mentions anything about the basis for these descriptions. Since cuir bouilli was still in use until fairly recent times, these descriptions may be based on methods of the recent past which they assume to be carry overs from medieval methods.
If I read this correctly, and I would love to entertain discussion that I am not, then in order to make something of "Cuir Bouilli" I can place my wet leather on or around its form when wet and either heat it until it shrinks (say in my oven: since 75C is about 167F), or immerse said form into boiling water (100C = 212F) until it shrivels into plastic hardness.
Rick Cavasin (Balderik)
NOTE: When heating the leather, do NOT touch the leather to any hot metal (Since using heated tooling materials is how book leather is embossed). Sitting it on newspaper works just fine to stop the heat though.
John Waterer's Leather and the Warrior has a complete chapter on Cuir Bouilli, and its history.
Hammering dampened veg-tanned leather will harden it up a lot. This is why sole leather is harder than belt stock. It has been compressed between rollers. The old fashioned method (in the recent past at least), was to hammer the leather you were going to use for shoe soles.
I have recently discovered that leaving leather out under the Summer Oklahoma sun will burn it hard as well. However, see the discussion under OIL.
By Other Volken (From the Crispin Coliquy, 26 May 2000)
Jackalope Also - When you say that you feel the examples you've seen of historical cuir bouili can't have been totally polymerized due to their degree of tooling - might it have been possible to actually do the tooling after the shrinkage, but while the leather is still wet?
Marc Carlson (Diarmuit) While I am fairly confident in that statement, I have some thoughts that it might be possible to place formed leather in a press to do the tooling, even if simply soaked and baked dry (since tooling takes so long). It might be possible to do this as well when "overcooking" the leather by boiling. I haven't tried it myself.
Experimentation is a good idea, since what we seem to be dealing with is a range of "hardness" imparted by the various treatments used:
Marc Carlson (Diarmuit) ...I went home and began to
experiment with a variety of things. The first batch of
experimentation was with a variety of pieces of leather, each
sewn to a shaped frame (a wooden dowel) and the dipping them into
water at a rolling boil, and holding them there for 60 seconds.
(For the precision fiends out there, while I'm not certain about
the elevation of Tulsa, Oklahoma, but I'm close enough to sea
level that my 3 minute eggs take about 3 minutes to cook).
Afterwards, I let them sit for 24 hours. The results were about
what I expected.
My second experiment was to take tooled leather (8-10 oz Cowhide) soak it down, hammer it to shape on a piece of wood and to stick it into an oven at 225 degrees. It darkened slightly, only part of it shriveled, and the rest looked like a 2-3 mm thick Bat-a-rang (However the tooling remained intact :) ).
Rick Cavasin (Balderik) Your differing results with the different weights of veg-tanned leather probably reflect the greater amount of time required to heat thicker pieces of leather....
David Friedman (Cariadoc)
1. Using leather (8 oz., Veg. Tanned) that had been soaked for several hours:
If you boil it for 20 seconds, it shrinks to about 7/8 the original size in Both directions, becoming correspondingly thicker. It also hardens a little. The result is comparable in strength to wax hardened 8 ounce leather. If you press it between two flat surfaces for ten minutes or so after boiling it ends up flat--the curling at the edges is negligible. If you boil it for 40 seconds or more the shrinkage is more substantial (to about 2/3 the original dimension) and the hardening (and associated thickening) much greater. Pressing it still gives you a flat piece.
If you boil it for 40 seconds, it shrinks to about 2/3 the original size in both directions, thickens to about the equivalent of 16 oz leather, and becomes quite hard--oddly enough, the complete hardening process seems to take several hours after cooling. The final result is comparable to 16 oz wax hardened leather.
Boiling for more than 40 seconds results in very little additional shrinkage, some additional hardening.
2. Using dry leather (8 oz., Veg. Tanned).
From these experiments, it seems clear that one could make scale or lamellar by taking your scrap, soaking it, boiling it 20-40 seconds, pressing it between two boards to make sure it hardens flat, then cutting out the individual lamellae or scales.
3. Shaping the leather (8 oz., Veg. Tanned):
In making things such as knees and elbows out of hardened leather, one problem is that it is hard to stretch the leather enough to get the piece as convex as you would like it. It occurred to me that boiling could help with this problem. The technique works as follows:
First cut out an oval piece of leather, soak it thoroughly. Then stretch it over a small bowl to give it a somewhat convex shape (more details on how you do this available if people are interested). Then stick a pin through the middle of it, with the head on the convex side. Then lower the piece slowly into boiling water, holding it by a pair of pliers gripping the pin (do you have an easier way of constructing a handle in the middle of a piece of leather?), and steadying it with a large spoon. The idea is to hold it for about 10 seconds with just the outside periphery of the piece (which is the bottom, since you have it convex side up) in the boiling water, then lower it for another 10 seconds so the area intermediate between the edge and the center is also under the boiling water, then finally submerge the whole piece for another twenty seconds. The result is that the periphery has boiled for about 40 seconds, the intermediate area for about 30, and the middle for about 20. The longer you boil it the more it shrinks, so you have just shrunk the periphery relative the center, which makes the piece more convex--also thicker and harder. Now you put it back over your bowl (or a smaller bowl if it fitted well over the old one before boiling). Let it cool. Let it dry.
I have now done this several times successfully. One piece I also successfully waxed--the others are still drying. I think waxing is necessary if you are using 8 ounce leather and the piece is supposed to be an elbow. 8 ounce leather boiled for only 20 seconds (the center of the piece) is not hard enough for me to trust it to protect the point of my elbow. Such leather both boiled and waxed is.
I've been told that I should use wax to make leather hard, is this true?
The other way to make leather hard is to take a piece that has been formed previously, place it into an oven, and dry heat it to about 200 degrees. Then take melted wax (bee's wax is traditional, but I have gotten just as good results from melted candles). Remember all the safety precautions you learned in art class as a kid for melting wax because it can be dangerous. When the wax is hot, and the leather is hot, take the leather out of the oven and paint the wax onto the leather (which will then soak it right up). Keep this up until the leather cools enough to not absorb the wax any more. Reheat the leather, and repeat until you are satisfied that the leather won't absorb any more wax (a good clue is that it's all the same color). Then let it cool. It will be extremely hard when it's done.
NOTE: When you are heating the leather for this you will be up at temperatures that will polymerize the chemicals in the leather in the presence of water. What this means is that if you get ANY water on the hot leather it will shrivel up and harden.
Ron Charlotte (Al Thaalibi)
I would have assumed that the hardening was more due to the wax infiltrating the fibre matrix (as Reed suggests that the Tannin Polymers do) and then hardening there. Also there is some concern about the weight added to the leather for the amount of strength given.
Ron Charlotte (Al Thaalibi)
Rick Cavasin (Balderik)
The reason that I suspect that it is the wax that is the prime factor, as opposed to the heat thickening of the collagen, etc. is a combination of the reports I have of wax impregnated leather re-softening to an extent in the summer heat, and the use of wax as an emollient in leather (also reported in Reed). I may be in error here, but it's just an opinion.
Rick Cavasin (Balderik)
Master Duncan Saxthorpe of Alnwick from the Kingdom of the West:
Cliff T. Wilkey
What are the relative melting points of beeswax vs paraffin etc... would it make more sense to use a higher melting point wax in favor of a lower one?
As far as I can tell, the Beeswax and Paraffin will melt at about the same temperature (and mix very well, if you want to stretch the beeswax a bit). Personally, I can't find a wax with a melting temperature hot enough to keep it from softening while worn outside in the sun (in Oklahoma), however, there is a form of crystal (styrene?) but that are available at hobby shops) that, when melted into wax raises the melting point. Good results can be had using about a 2:1 ratio of paraffin to beeswax.
Unfortunately, the hotter the melting point of the wax, the hotter the oven needs to be to get the leather hot enough to readily absorb the wax. I've had too many pieces suddenly shrivel up to be eager to risk the extremely hard waxes (although I suppose I will give in eventually).
Is there any evidence for waxed leather in period? Do we speculate that the evidence has rotted away? Or is it unlikely that hardened leather was ever used for armor?
Speculation: It is conceivable to me that, after introducing an organic waste product, such as wax to leather, it might rot away faster than ordinary leather. It is also conceivable that after more than four hundred years of burial, there is no way to distinguish the waxed forms.
It is, however, also reasonable to assume that waxed armor was not used either in period, or during any of the classical periods for armor, either because it was too expensive to waste, to difficult to get a regular temperature from an oven that was low enough not to destroy the leather, or some other reason.
I would have suspected that the Mediterranean Civilizations might have had trouble with it due to the sun's heat, but I have been informed by the people I have armored in the stuff that fighting under the Texas/Oklahoma sun hasn't posed a problem and that while the leather softens a bit after an all day thing, it rehardens very quickly.
Please Note that there is NO Evidence that I know of that Waxed Leather was used for anything other than some Elizabethan era bottles, cups, knives scabbards, etc.
By DR OBUV (From the Crispin Coliquy, 21 January - 27 January 1999)
In fact, it works better since the wax doesn't have to soak through the skin to get to the flesh. I don't know if heating it will loosen the fur at all, or do other weird things to it.
I have never used the alcohol to work oiled leather, however don't be surprised if residual alcohol doesn't mess up your wax (since that's how you strip wax off of shoes). Waxing the oiled leather may make a horrible mess, but if you are patient it will eventually even out (I have a cup that oozed oily wax for months, but is now a prime example of hard leather).
They may be chrome-tanned, essentially using mineral salts. The wax *should* harden them, but I've never tried it on pelts, and if you use too much you may get waxy fur.
Some people feel that there should be NO boiling in oil AT ALL. Oil is used to soften leather, and all boiling it has gotten me is a soft squishy mess better left undescribed and buried, not to mention this is how one deep fries meat.
Rick Cavasin (Balderik)
Now that you mention it, I have a leather bottle that I made last year that, for reasons better left unmentioned, I soaked to the brim with Neatsfoot oil, and then left in the window of my spare room to let the oil settle. I forgot about it, and after three months of the Northern Ansteorran summer sun on it, the puppy had baked hard. I had a similar experience with the front flap of a map case I left in the rear window of my conveyance. It too had been heavily oiled with Neatsfoot oil.
Ron Charlotte (Al Thaalibi)
Rick Cavasin (Balderik)
I hadn't considered it, since Linseed Oil can be (I am informed) somewhat explosively flammable. [of course, that's while it's wet. When it's dry it stabilizes, unless fire is applied directly.]
Ron Charlotte (Al Thaalibi)
I would like to point out that oilskin is made from UNboiled Linseed Oil.
After thinking about it, I can think of a number of historical applications for leather, such as shield facings, where rawhide might make more sense, but there is no indication in the texts I can find.
A number of experiments have been made using rawhide as shield facings and armor. Knives didn't even cut or pierce them, and they REALLY tried to. We talked about shooting at them with arrows but never did. Maybe next year. Rawhide could be a good material to make armor of.
Waterer suggests that in a quick examination of rawhide in a site, it is often mistaken for Cuir Bouilli, and has been found used in knife scabbards, etc.
Rick Cavasin (Balderik)
Rick Cavasin (Balderik)
Rick Cavasin (Balderik)
Finally from other information I have received, it would appear that since rawhide is more susceptible to rot than tanned leather, it might have been used for other things, like shield facings, and we wouldn't know. It would also be susceptible to rot in use, while on campaign, etc. This may have restricted it's use in damp climes. (Rotting Rawhide Stinks!)
This may seem like a naive question to some, but what happens to rawhide when it gets wet? Doesn't it get soft and pliable?
As a rule, you have to soak rawhide for some time to get it to soften at all, and quite some time to make it pliable. When you stretch it while wet, it shrinks as it dries.
On the other hand, while certainly rawhide will become "soggy and stretchy" after emersion in water for an extensive length of time, it has not been my experience that rawhide, simply exposed to moisture, will be made malleable. Granted, changes in humidity can make it not entirely suitable for things like knife scabbards, as it can swell up slightly, although this can be planned for by making the scabbard slightly larger than needed. I assume the same can be done for armor.
In Waterer's Leather Craftsmanship (1968), page 116:
Waterer's Leather and the Warrior (1981) page 5 shows a photo of the Somali shield "made from layers of untanned hide". Page 47 shows a picture labeled "Body armor (Shupenpanzer) covered with scales of untanned hide with hair remaining. "And just to give some support to David Friedman (Cariadoc)'s suggestion:
Also some sources suggest that different forms of raw, or undressed, or green, hides have different properties, although I have not been able to experiment with this yet. It is suggested that buffalo hide (parfletche) when raw is in fact softer and more pliable than cow, which is why it was used for so much more by the Native Americans.
On the other hand, this may have had a lot to do with the methods used for making the rawhide. Native American methods may have depended on bacterial action to remove the hair from the hide, although it is known that by the time of contact they generally used alkali to depilitate their skins for rawhide, especially on the Plains where the rawhide culture was strongest. Wood-ash lyes were most frequently used but lime was used by the Comanche. This is documented to the very earliest descriptions of Plains rawhide. See John D. Hunter (1823), George Catlin (1838) and Colonel Richard Irving Dodge (1883). It is arguable whether bacteriological depilation would have had more of a softening effect on the hide than the alkali depilation practiced by the Europeans and as described above, or whether the reverse would be true (I've never tried either myself, so I can't say for a certainty. However, more experienced leatherworkers have told me that hides depilitated through bacterial action may in fact be harder, since the mucopolysaccharides -- a mucus, are removed or broken up by the alkali. Alternatively, another Native American method of depilation was by scraping, which would have removed the upper or 'grain' layers of the hide, which are more tough and compact than the underlying layers. Without them, the rawhide would be softer and more pliable.
There is a difference of opinion about the differences and variations in methods used and whether they would have any impact than the species of animal in use (particularly when considering animals as closely related as the buffalo and cattle). Others, including Waterer feel that differences in age, species, and even gender of the animal can make a difference in how the leather turns out.
Is it possible that some of the period examples of leather we've dug up have some how "Self tanned" over the centuries to be harder to distinguish from mere leather? I'm not sure what you mean by 'self tanning', but rawhide/parchment, with time undergoes a natural oil-tanning process whereby residual oils present in the hide oxidize to produce aldehydes that 'tan' the hide.
Leatherworking in the Middle Ages - Cuir
Bouilli/Hardened Leather. Copyright © 1996, 1999, 2000, 2001, 2003
I. Marc Carlson
This code is given for the free exchange of information, provided the Author's Name is included in all future revisions, and no money change hands.