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A discussion upon the topic: hardening Leather with Wax and Oil.

American Leather Experts.

<Pesch> 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 „paint“ 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. tanned leather. Only these will absorb the wax properly to decently harden.

<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.

<Roth> I would have assumed that the hardening was more due to the wax filtrating 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.

<Pesch> 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.

<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 except. While I hardened my armour without wax, I added the wax afterwards to enhance the effect.

<Roth> 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.

<Balderik> The cuir bouilli effect, (ie. hardening by heat), is, as far as I know, nonreversible. 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 armour does not soften much in the sun. In cases where peoples' armour 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 (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 carnuba 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 &bdquuo;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 reshaped by heating in an oven.

<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.

D. What are the relative melting points of beewsax vs parafin 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 Parafin 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).

E. 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, a bit more 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, knife scabbards, etc.

F. 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.

G. 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).

H. 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.

3. Oil?

<Roth> 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.

<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.

<Rondeau> One word of warning: do not imerse 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?

<Roth> 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.

A. Linseed Oil as Varnish

<Pesch>  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.

<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 armour (candidate for one of the most offensive suits of armour 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.

<Roth> I hadn't considered it, since Linseed Oil can be (I am informed) somewhat explosively flammable.

<Pesch>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' 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.

Remarks of the editor
A few very interesting opinions. Personnaly I am fully satisfied with the Cold and Hot water method for forming leather. Wax is applied as a misture barrier and or cleaning agent. People who acquire my pieces of armor are informed to wet the piece and wear it till dry. I agree this may be uncomfortable to some but it helps insure the piece conforms to the person who is to wear it. Wax as i am informed as a hardening agnt is great for smaller pieces, for example bottles, pouches, drinking vessels and sheathes. The Leather Museum in Offenbach is very informative when it comes to the wax hardening methods and and applications. Balderik has a very great understanding as evident above. Cliff Wilkey tells of forming leather using wooden forms, something i am aware of as well although dowsing with boiled water and not wax. Seeing as how hard evidence of armor made from leather has not survived the periods of time, except for the roman loricons, which in my opinion were more from accident than designed. Soldiers would wipe their hands on the armor. This transfer of fat helped preserve the armor. As an old soldier, even though protection is of great importance, lighter loads to carry were always appreciated.