How do I make Cuir Bouilli?

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.

Simple Soaking

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.

Hot Water Soaking

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)

"Reed goes into detail about the physical/chemical makeup of leather and the effects of wetting/heating. Leather which is simply soaked in room temperature water and then shaped and dried gets harder (not that hard) and retains its form. The hotter the water, the more structural changes you get which results in harder leather. Experiment with scraps to find the right temperature."

Boiling Water Soaking

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!.

A Variation on Boiling Water Soaking

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.

Baking

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.

Page 79: "Some of the properties of vegetable tanned leather have already been mentioned. If the tannage is sufficiently long, the leather tends to be full, with a round and generous handle: i.e., it is a filling tannage. It shows high resistance to perspiration fluids (accounting for its use in various parts of shoe construction, e.g. the insole), whilst it can be embossed easily to allow designs and art work generally to be applied to the surface of the leather. It possesses strange thermal properties and one disadvantage is that wet, vegetable tanned leather begins to shrink above 75 degrees C and so lose its shape. Nevertheless this property has been widely exploited. The moulding of this type of leather was known in Saxon times in Britain, and during the Middle Ages both here and on the continent of Europe it was extensively practiced. Chaucer, in the fourteenth century makes frequent reference to the peculiar form of moulded leather known as cuir bouilli. After thorough softening in water at ordinary temperatures, the leather can be formed or moulded into the most remarkable shaped which on drying retain a fair degree of permanence. The wet-moulded leather shape can be set more permanently by drying under a moderate heat, the skilful choice of temperature determining the degree of rigidity obtained. A quicker process which produces extremely hard and rigid articles is to dip the moulded shape into boiling water for about 20-120 sec, a practice which gave rise to the name cuir bouilli. Such a process involves the partial melting of the aggregates of fixes tannin in the leather. near 100 degrees C these become plastic and can be made to flow and redistribute throughout the fibre network. On cooling, the latter becomes embedded in what is virtually a tough three-dimensional polymer network or resin, not unlike the more modern materials made by condensing formaldehyde with substances like phenol, urea, or melamine (e.g. Bakelite and the aminoplastics)."

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)

"As Reed says, the choice of temperature determines the degree of hardness. I think the trick is to not heat it to the point of 'shrivelling'. At this point, I think the finished product will start being too brittle to be useful for armor. I think the trick is to stay right around the 75C mark so that the leather is on the verge of shrinking, so you get the hardness without the shrivelling. I hardened my armor plates by the soaking/baking process. They were quite hard before I waxed them, but had remained true to their molded shape (ie. not shrivelled). The dipping in boiling water probably requires a bit more practice to get the duration just right so that the leather hardens without shrivelling."

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

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.

Wax

See Below.

Sun Burning

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.

LATE ADDITIONS:

By Other Volken (From the Crispin Coliquy, 26 May 2000)

"I just stumbled across some old info on cuir bouilli in:  Louis Figuier, Les Merveilles de l'Industrie, Paris, 1873,  chapXX,  pp.446

Here a translation:

"We will finally note a curiosity in leather fabrication specially made in Turin, Italy. Once the leather is tanned and finished it is deteriorated as follows, under pretension to ferment it. The leather gets wetted and then piled up; and that the leather heats up easier, the wetted hides are covered with straw. The hides are turned once or twice a week and then brought to the drying rack. One obtains this way a blackish, breakable leather, which is called **cuir lissé bouillis**. (Litt. slicked boiled leather) It is a very bad preparation, because on almost burns the leather, and we obtain a bad product.

A cuir bouilli is a nearly decomposed material. Its fibers are disintegrated and don't have the firmness and elasticity produced by our excellent French tanneries. Luckily the good slicked leather replaces little by little the cuir bouilli."... end of citation

I found this part in the section where Figuier talks about finishing the tanned leather. I guess we added one more mystery to the boiled leather enigma."

Tooling the Hardening leather

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

Experimentation is a good idea, since what we seem to be dealing with is a range of "hardness" imparted by the various treatments used:

Somewhat Stiffened:
Caused by simply soaking in water and drying. (Examples: Most things that have been merely tooled, but not much else. For those unfamiliar with the tanning process, this is simply reversing the 'Staking' process. When leather is tanned and is in the process of drying, it must be worked or 'staked' to prevent it from drying stiff. The amount of staking, to some extent, determines the final softness. Soaking the leather and letting it dry reverses the process).

Stiffened:
A quick soaking in water and baked. (Example: Armor that has been sweated into and dried in the sun).

Hardened/Polymerized:
Soaked for a LONG time in water and baked dry. (Example: Cuir Bouilli as Rick Cavasin (Balderik) and Waterer have been describing it. This *may* also include the attempts that have been soaked with oil and baked hard in the sun).

Totally Polymerized:
Boiled in Water until it shrivels and shrinks. (Example: Marc Carlson (Diarmuit)'s wrist brace experiment described below).

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.
The 8-10 oz Veg. Tanned Cowhide turned dark brown, shrank and hardened.
The 5-7 oz Veg. Tanned Cowhide turned black, shrank a LOT, and hardened.
The 2-4 oz Calfskin turned dark brown, and shrank to fit beautifully.
The 5-8 oz Latigo Cowhide had no noticeable changes at all.
Elk hide (tanning method unknown, but probably oil "tanned") Darkened slightly, and only stiffened VERY slightly. The Latigo calfskin, Horsehide and Buckskin had the same results as the Elk hide.
Heartened by the success of this, I took an old tooled wrist band (10 oz Cow hide), wrapped it around a bottle and dropped it in the boiling water for 2 min. Most of the tooling vanished, but it is currently harder than anything I've yet made.

 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).
The result seems to be somewhat faster hardening, but also a lot more curling, distortion, etc.

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):
It occurred to me that one could take advantage of the shrinking produced by boiling. One of the problems I have had in making bazubands and greaves is the difficulty of making the portion that covers elbow or knee sufficiently convex. This is basically done by stretching the middle part of it. Shrinking the edge should have the same effect.

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.

Wax

I've been told that I should use wax to make leather hard, is this true?

Basics

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.

A discussion on other views of Wax and Hardened Leather

Ron Charlotte (Al Thaalibi)

"In my own experience with wax hardening of leather, 200 degrees is -way- too hot. I normally melt my wax in a "double-boiler" arrangement in a pan set in another pan of water. Try water shaping the leather first, then, when it has dried and set into the shape you want, immerse it into the melted wax. High heat isn't needed just enough to keep the wax liquid. If the piece is too large for your melting pot, heat the piece with a hot hair dryer/heat gun or place it in the oven long enough to get hot then "pain" it with the melted wax, reheating the piece as needed.

"You really need to stay away from "oil-tanned" or treated leathers for this purpose, use an alum or veg. tannin tanned leather. Only these will absorb the wax properly to decently harden. "

Rick Cavasin (Balderik)
"To the best of my knowledge, this is somewhat misleading. For an excellent description of the chemistry involved, see Ancient Skins, Parchments, and Leathers by R. Reed, but the gist of it is that it is not the wax that is hardening the leather, but the heat. Cuir Bouilli can be made WITHOUT WAX (although using wax helps by making the leather denser, heavier, and resistant to water). The chemical/structural changes responsible for the cuir bouilli effect are only possible with veg-tanned leathers. Other leathers may be stiffened somewhat by heating and adding wax, but it will not be cuir bouilli.

"Given that a good deal of hardening can be achieved without resorting to the use of wax (by simply drying under heat) and that waxing provides some enhancement, my argument was that those who wax the leather directly are probably getting most of their hardening from the heating needed to apply the wax, not from the waxing itself."

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)

"I've used both the cold water/wet molding and the hot water methods of shaping leather as well. I simply find that the addition of wax produces pieces that stand up to the rigors of SCA combat abuse, especially here in the humidity and erratic weather of Trimaris (Florida), far better than the other options."

Rick Cavasin (Balderik)

"Oh, there's no doubt that wax *helps* by increasing the density and water resistance. The point I was trying to make is that the majority of the hardening is related to the heating. Much of the hardening many people achieve may be a result of the heat they apply in order to get the wax to soak in, not from the wax itself (people who use wax hardeners excepted). While I hardened my armor without wax, I added the wax afterwards to enhance the effect."

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)

"The cuir bouilli effect, (ie. hardening by heat), is, as far as I know, non-reversible. The softening in the sun would be the removal of any enhanced stiffness imparted by the wax. If the softening is substantial, I would suspect that little heat hardening was achieved. My own armor does not soften much in the sun. In cases where peoples' armor does soften appreciably, I would say that you are correct, that the wax is in fact providing the stiffness.

"My own feeling is that the added stiffness, density, and water resistance is well worth the increase in weight (but then my life doesn't hang in the balance, as it would for the medieval warrior).

"Another factor to consider is that the wax may have been a significant expense in Medieval Europe. Bees wax was in high demand for candles. Waxing leather that could be adequately hardened without it might have been regarded as extravagant. Unfortunately, I must plead ignorance regarding the relative market value of wax in period.

"Perhaps water resistance would have been achieved using something more economical like tallow which would, I suspect, have had little additional hardening effect."

Master Duncan Saxthorpe of Alnwick from the  Kingdom of the West:

"You are welcome to include this in future articles, if you wish: Use a mixture of half pure white beeswax (it smells a bit less sweet) and half pure Grade I carnauba wax (the really, really hard stuff). I use a large commercial roasting pan which barely fits on my gas BBQ and do this outdoors... having some concerns about fires and some real trouble removing the wax mixture from a even stainless steel counter top! I gentle heat the wax over medium heat with a barrier of heavy duty tin foil between the grill and the pan, to ensure more even heat distribution. When the wax is fairly hot (a scrap of heavy sole leather forms numerous small, well-distributed bubbles on the rough side within one minute) I "boil" my cut, died (and dry) leather pieces for about 2 to 4 minutes. As you pointed out, the leather can be cooked and ruined by too much heat, but this heavy grade of leather seems to be more forgiving than even 10-12 ounce leather. Anyway, when the leather appears to be well soaked I remove it from the waxing pan, wipe it clean with a towel I never want to see again, and shape it under running water. The leather sets up nicely within a few minutes and takes about 12 hours to completely cure. This wax mixture holds up very well in our California summer sun with minimal softening (about twice as firm as bees wax armor) and can be re-softened and re-shaped by heating in an oven."

Molding

Cliff T. Wilkey

"From what I have heard, the leather was placed into a "mold". This mold consisted of two *large* blocks of wood, and the shape of the leather armor was carved into these two blocks. The leather was put into the mold and boiling wax was poured in. Then it was left to cool."

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.

LATE ADDITIONS:

By DR OBUV (From the Crispin Coliquy, 21 January  - 27 January 1999)

"The cuir bouilli is the leather of ox or cow 'bouilli' in wax mixed with various gums, resins, and pastes, which are kept secret by the sheath and scabbardmakers. Article 13 of the statutes of the sheath and scabbardmakers of Paris, which are dated 12 September 1560, allows that it is forbidden for the trade to make leather bottles with any other leather than cow or ox, because other leathers are not suitable, and that the above-mentioned bottles must be 'boulues' with only new/fresh wax and nothing else, and stitched with double-seams from both sides [i.e. double-looped hand stitch, not a running stitch-ED], strong and durable." -- Roland de la Platiere, 1788 in 'Encyclopedie Methodique' [Paris,1790]

Key here are the various ways in which "bouilli" and "boulues" are used. Literally "boiling" the leather, as in dunking it into a vat of hot waxes is the immediate and easy assumption, but upon removing the object and its "last", the waxes would rapidly cool and leave an object encased in a mess solidified waxes.

"The Shoemaker uses several kinds of wax. [...] Bootmaker's jacking/wax is made from two pounds of collophony [NB -- highly refined/brittle pine rosin from Colophon, Lydia. The German edition has 'pitch' or 'black pitch' here] and one pound of yellow wax [NB -- raw beeswax] with lampblack [NB -- powdered carbon from oil fires] to suit, all melted together. This jacking/wax is used by Bootmakers to penetrate the leather of jack boots and to make them stiff as wood... The Shoemaker uses this wax for certain heavy shoes that the lower sort and peasants wear, but while making it he reduces the amount of colophony."

"Having one pair of boots... over their boot trees and previously wet, but now dry, take a coarse wood rasp, which is rubbed over the whole boot-leg to remove the fluff which stands up on the flesh; after this you proceed with the jacking/waxing... The place for jacking/waxing must be a room with a chimney, paved or tiled [NB-- "...where there is no fear of fire" in one edition]; near the top of the chimney, outside, is attached an iron chain which dangles to within six inches of the floor or there-abouts. You ready yourself for jacking/waxing by putting a small portable stove or lit brazier on a table to your left, on which you place a kettle containing the following recipe: One pound of yellow wax, two pounds of colophony, which is pine rosin, and lampblack to suit. You also furnish yourself with a swab, this is the name of a large dauber formed from a bundle of linen rags bound together, and have on your right, on the ground, some loose straw... Begin your task by lighting a little straw, which you wave under the bootleg to singe it, in other words to burn the rest of the fluff from the leaher that the rasp did not remove; afterward dip the swab in the BOILING [NB -- emphasis added] jacking/wax with which you coat the entire bootleg. Then continually rotate the boot-tree with your hands over a steady straw fire so that the heat makes the jacking/wax penetrate. You put on six sucessive coats in the space of an hour, being very careful to occasionally moisten the bootleg so it will not scorch, and so it takes two hours time to jack/wax one pair of boots. The bootleg now jacked/waxed, leave it to cool... When the bootleg has been jacked/waxed, and once more is thouroughly cold, it is full of lumps caused by the boiling jacking/wax with which it was coated and saturated; to remove them take an old knife, and using the blade as a scraper, scrape off all these lumps, then rub with a piece of cold wax that you spread very evenly with a stiff brush or burnishing stick, etc., and you finish-off by polishing and shining with the palm of your hand". -- M. de Garsault, 'l'Art du Cordonnier' [Paris, 1767]

"Lacquered [NB -- literal translation from German] Boots -- A type of stiff boot with or without tops, which are made with the flesh out in the same manner as the jack-boots, and which are given a glossy finish with the following lacquer:

Powdered gum mastic... 1/2 oz.
Powdered ivory-black.... 1 oz.
White poppy oil... 1 oz.
Spikenard oil... 1/2 oz.
Asphalt... 1/2 oz.
White wax [*]... 1/2 oz.

Add the ingredients seperately, mix in the oils."--D. G. Schreber, 'Der Schuster' [Leipzig, 1769].

While not necessarily a jacking/wax, this formula is interesting. Schreber discusses the superiority of all English boots, and the polishes for them, but says they can't quite get it right. [*, this usually denotes highly refined beeswax that has been rendered and filtered to the point of being nearly pure white--harder than raw yellow beeswax].

"For Jacking The Flaps of Cartridge Boxes
Let the flesh side of the leather be shaved smooth, & put outside. When 'tis well dried & warmed, rub it with the following composition, of:  6 pounds of rosin; 1 pound of beeswax; 1/2 pint of spirits of turpentine} all dissolved together and put on hot.  Frequently hold the flap to the fire till enough of the stuff enter the pores of the leather, rubbing well. When cool, size it... with a size made of rawhide, rubbing it well.   If spirits of turpentine cannot be had, beeswax will answer; but it does not penetrate the leather so quick... To save the jacking stuff, the flaps should be cut out before they are jacked; but it is said that the jacking should not come where the leather afterwards to be sewed as it will be too hard; ... You will try the jacking, both before and after the sewing, and determine which is the best way." -- Timothy Pickering on Jacking cartridge box flaps, Vol. 56, p. 5 [No date, c. 1775]

"We would go to a turner or wheelwright, and get head blocks turned, of various sizes, according to the heads that had to wear them, in shape resembling a sugar loaf; we would then get some strong upper, or light sole leather, cut it out in shape, close it on the block, then grease it well with tallow, and set it before a warm fire, still on the block, and keep turning it round before the fire, still rubbing on the tallow, until it became almost as hard as a sheet of iron... We made the scabbards of our swords of leather, by closing on a pattern of wood, and treating it similar to the cap." -- Recollections of a Revolutionary War Soldier [reprint 1854 edition]

Now then, as we have before us an accumulation of descriptions of the process of hardening leather with heat, pitch, rosin, etc., let me launch a question... since "bouilli", in Abel Boyer's 'Royal Dictionary Abridged' [London, 1700] gives, in addition to "boiled", "warm, boiled, seething, or bubbling up", "to gush out", and even "baked" in connection with "boul"--derived words, what are we led to believe? Under "cuir" he gives "visage de cuir bouilli'; a wainscot face. P. Faire de cuir d'autrui large courroye, To be free of another man's purse." Now wainscot seems to be a stretch, but the connection with wood [as in Garsault's "hard as wood"] is tempting..

...Firstly, just because Chaucer mentions leg-guards of "quirboily", how/why do we assume it was heat and water only, rather than heat and "bouilli" painted-on? Why not dope-hardened leather? Waterer's assumptions aside, why couldn't Chaucer's "quirboily" be doped-hardened leather in the 14th c. as well? Post 1560 in England and France, the suggestion is saturated with rosin, etc., just that the Brits start calling it "jack"ed by the 17th, and drop the Franco-phonic "quirboily" from the vocabulary all together.

Any confusion here regarding "waxed leather", which I agree is NOT "cuir bouilli", is purely accidental I assure you. The problem is in the French use of "cire" for bloody everything vaguely resembling a waxy substance. A bit of care, however; in my translation from Garsault [above] I carefully wrote jacking/wax, where in the French text it's just "cire" [wax], though the French author seems to use "cire" for everything from currier's dubbing, shoemaker's "coad", and "machine" [white coad], up to and including what Pickering just calls "jacking stuff". Garsault also discusses "heavy waxed shoes", [gros souliers cire's]. In this case he says that the un-dyed and un-curried shoe uppers are smeared with a wax [cire] composed of "mutton tallow, a little wax [cire again -- beeswax presumably] and a little more lampblack". This mixture is applied with a dauber dipped in "le cirage chaud" [the warm wax-mix]. Nothing in the text suggests that this form of "wax" stiffens or hardens anything. Quite the contray, it loads it with warm tallow. As a matter of fact, the English term "waxed leather", as in waxed calf, etc. merely refers to a heavily grease-stuffed, blacked on the flesh, uppers leather. In fact, elsewhere Garsault says that blacking on the flesh is more "English", and the French usually blackened their uppers on the grain with dye or stain rather than sooty grease. In French, "waxed leather" is clearly NOT "cuir bouilli".

Finally, why are Chaucer's "quirboily" leg-guards NOT dope-hardened leather? Shouldn't leather armour be hard? I suppose all I'm at here is this, since "cuir bouilli" meant doped-hardened leather from 1560 on in France, and became "jack"ed leather in 17th c. England, why must it mean something different in Chaucer? Are we just trying to leave room for Waterer to be "right" about the heat/water only theory? Impregnating items with rosinous substances to alter their texture hardly seems out of keeping with the most ancient leather-work

Oliver Baker makes a case for all hardened "jack" type leather vessels being essentially British in origin.

Would it be possible/effective to wax the leather piece from the inside instead of outside?

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.

Waxing Oiled Leather

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).

Can I wax tanned hides with fur intact?

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.

Oiled Leather

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)

"Boiling oil is way too hot. I've never tried the boiling water method described by Reed, but he does specify that the immersion be very brief (depending on thickness, etc.). The hardening only works with vegetable tanned leathers. "

Ben Rondeau

"One word of warning: do not immerse any leather into the (presumably hot) solution while the leather is cold. I did this once with a lame for a pauldrin. I got to watch it deep fry. It came out looking like a piece of bacon. Not something that was terribly useful.
Perhaps stitching to a form, then boiling in oil?? Any ideas?"

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.

Linseed Oil as Varnish

Ron Charlotte (Al Thaalibi)

"We've all heard the mistaken notion of boiling leather in -oil- to harden it. It was recently pointed out to me that boiled -linseed oil- is a varnish. Has anyone tried this as a medium. I'm going to give it a try with some sample pieces once I'm done with my current slate of projects, but if anyone else has come across this and tried it, I'd love to hear."

Rick Cavasin (Balderik)

"Boiled linseed oil has additives to make it dry faster. Not sure what these will do to the leather. If the varnish dries stiff, you may have problems with cracking. I have dressed leather with unboiled linseed however. Because it oxidizes at a lower temperature than other oils, it yellows the leather much more quickly than neatsfoot oil. The end result is that you end up with a partial oil tannage. I'm not sure about the long-term stability, as the leather I dressed was some alum-tawed, hair-on, moose hide from which I made my first suit of armor (candidate for one of the most offensive suits of armor of all time - both in looks and smell). It hasn't been used in ages, and the leather is falling apart. Not sure if it's because of the linseed, the tawing recipe, or the repeated cycles of being soaked in sweat and then dried. I give away bits to people who tie flies"

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)

"True enough, the commercially prepared stuff has drying agents (without reading the can, probably alcohol or mineral spirits). Based on Cennini's The Craftsman's Handbook, Theophilus's On Divers Arts and Alessio Piemontese's The Secretes of Alexis of Piemont; and their instructions for boiling linseed oil down into a varnish, both with and without the addition of lac resin, starting with the raw stuff and adding the leather to it or vice versa might work. In fact, the place where Cennini discusses rendering the oil down by sun-cooking makes me wonder if applying the raw oil to a piece and subjecting it to slow heat (sun or low oven). I think that I need to pick up a gallon and start tinkering...preferably outdoors on a hot plate or propane stove, all of the period writers mentioned above make a point of pointing out the flammability of the stuff.

"As far as the stiffness factor, I've used tung oil varnish for a finish on a couple of belts, and it made for a nicely flexible finish. I'm hoping that linseed oil will behave in a similar fashion."

I would like to point out that oilskin is made from UNboiled Linseed Oil.

A short discussion on uses for Rawhide

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)

"Remember that Parchment is a form of rawhide."

Tibor

"...Don Tivar, as part of his study of the rapier, has done studies of how much force is required to pierce human skin. His research lead him to use rawhide soaked in water, which he was told most closely matched human skin's behavior. (Some coroner research, I gather. Memory dims). It cut with about 5 pounds of pressure, and pierced with substantially less. So, dry rawhide is relatively impervious, but thoroughly soaked rawhide is barely impervious. Try not to leave those shields out where the dew might get them. And, don't make armor of it if you perspire..."

Rick Cavasin (Balderik)

"The ease with which a piece of dry rawhide can be soaked depends on how much it was stretched while drying, and how much residual oil is left in the hide (ie. parchment is easier to wet than rawhide because it has been stretched more and has less residual oil, generally)."

Matt Richards

"Native American tribes would take buffalo rawhide and deliberately heat it to the point that it shrink and thicken for use as a shield. This is well documented and I could find the sources if you are really  interested. Another technique commonly used was to coat their rawhide containers with 'sizing', which would increase the water resistance.    Typical sizes included prickly pear cactus juice and hide glue. And while neither of these is 'water proof' they are both slow to absorb water. I think your statements about how rawhide would not significantly wetten under normal use unless left soaking in a puddle are quite accurate. While rawhide does absorb enough moisture from rain or dew to  bother drummers, it takes a very long time for it to get 'wet'."

Tension and Rawhide

"Rawhide changes tension radically with humidity and moisture, far more than tanned leather. This would tend to limit rawhide in a structural application."

Rick Cavasin (Balderik)

"The problem with rawhide is that it can become dimensionally unstable if it becomes wet and is then dried. Parchment/rawhide can generate an impressive amount of tension when it dries (I've had goat and deer hides warp and break the frames I use for parchment making). Tanned hides are much more stable, and are much less prone to rot.

"A piece of rawhide, left to dry on it's own, will shrivel up to become tough, hard, horny, and semitransparent. Usually, in making rawhide/parchment, it is customary to stretch it on some sort of frame so that it dries into a flat sheet.

"If it is subsequently soaked in water, and allowed to dry without tension, it will shrivel up more or less like a fresh piece of rawhide. And parchment/rawhide can generate an awful lot of tension when it's trying to shrivel up."

Other Problems with Rawhide

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!)

What happens to Wet Rawhide?

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:

"Shields have long been made in India of layers of raw skin. The most prized were those in which, by careful selection of almost flawless skin, the resultant laminated material was nearly transparent."
"The Somalis made a shield of an untanned hide in an unorthodox form but in this case the outer surface is roughened to make it completely opaque and resistant to moisture."

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:

Page 53: "...But in wet or damp conditions it will quickly revert [to a more softened condition], putrefaction will commence and eventually destroy it. Therefore for any purpose likely to be involved with changing atmospheric conditions, the surfaces must be protected; the traditional way of doing this was to lacquer it, as was done in China and Japan. Rawhide scales would have been very tough, light in weight and long lasting if properly looked after. They were used for lamellar armor in the Far East..."

Variations in Raw Hides

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.

In Situ Self Tanning?

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.