(This section was written almost entirely by Rick Cavasin (AKA Master Balderik email@example.com) and is copyrighted by the him. Its use here is with permission)
Here's a quick tutorial on the different 'types' of
skin/leather products that were available in period:
(It should be remembered that in period, the three types of tannages were sometimes used in combination.)
If you've got a whole pile of leather scraps from somewhere,
how do you tell whether it's vegetable or Chrome or some other
kind of tanned? My immediate guess, since it comes in a wide
variety of interesting colors, is that it's NOT vegetable
leather, but how do you tell? (Boil it, and see if it gets
Balderik As I mentioned earlier, about the only type of true oil-tanned leather widely available today (to my knowledge) is chamois of the type used in garments and for washing cars. As this type of leather is fairly easily identified (light brown, stretchy, suede-like on both sides, may smell like whatever oil was used) we can probably rule out oil tanned. Veg-tanned leather is usually tan to light brownish. Although it is usually sold undyed, even if it is, cutting it and examining the cross section should reveal the characteristic color. Because of the applications for which it is typically prepared, commercial veg-tan is fairly stiff and not very stretchy.
Alum tawed skins are fairly rare these days due to their sensitivity to moisture.
Chrome tanned leather is probably the most common leather nowadays. Used for everything from garments to shoes. Unless it is dyed straight through, you can usually detect it by cutting and looking for the characteristic light grey blue color that the chromium sulphate imparts to the leather. The leather can be quite soft and stretchy.
As different types of leathers tend to be rather distinctive, once you see the different types identified, it's usually pretty easy to identify leather. There are oddball leathers that can be hard to peg, but most of the stuff that is mass-produced today falls into one of a few categories. Go to a place that sells leather, and look at some veg-tan, and then look at some chrome-tanned. See and feel the difference. Works for me.
Well, the color of the animals fur can contribute to the color of the underlying skin, but it depends on how much of the pigment/hair fragments are removed in the unhairing process. Modern methods of hair removal are pretty effective, especially on calf.
More important is where the tannin came from. Different plant materials will give different colors. Leather tanned with oak bark will be different from that tanned with sumac leaves, which is different from that tanned with Acacia pods. This is especially true of leathers tanned by period methods. Today, there is incentive to remove as much of the coloring matter as possible from the tanning liquors so that the leather will be pale, and therefore easier to dye (at least in lighter shades).
Diarmuit If your leather is "flesh" tone (Caucasian) or something in that visual range, dry and stiff (depending on how thick it is) like cardboard, it is vegetable tanned. Examples include unstained Baseball Gloves, Saddles, and most SCA armor. Vegetable tanned leather absorbs water fairly well. Balderik I'd sprinkle a few 'probably's and 'usually's in there. These leathers are like that because they are, to some extent, made to be that way. Veg-tanned leather can be soft, greasy, etc. It just isn't usually made that way. High quality bookbinding leather is often veg-tanned, but it doesn't have quite the same feel we usually associate with veg-tan.
Diarmuit If it has hair, it's probably NOT vegetable tanned. If it's soft, thin and flexible, it's *probably* not v-t, but rather "oil tanned", but I'd be careful here. Some leathers that are called 'oil-tanned' are really just chrome and/or veg-tanned leathers which have been heavily fat liquored (all leathers are fat-liquored to some extent). True oil tanned leathers are leathers that are impregnated with oil (the grain layer is typically removed to facilitate penetration from both sides), and then the oil is oxidized (by smoking in the case of Native American tradition), and the residue is often washed out. Chamois, of the sort used to wash cars is about the only true oil-tanned leather manufactured commercially these days (to my knowledge). Buck/brain/smoke tanning, the Native American variant of oil-tanning, is not performed on an industrial scale as far as I know.
Note the best calfskin (IMO) is V-t, but is soft and flexible and thin.
If it's chromium Tanned (or Latigo) it will often have a thin white layer if you cut it in half. That line is the chemicals that remain in the leather. Sometimes, though, they're dyed right through so the characteristic (White, Gray or Blue Gray) color is hard to spot. Veg tanned scrap is generally thicker 4 oz>, and either oiled or waxed if finished at all.
I'd say that most hides are chrome-tanned these days. Most garment leather is Latigo. DO NOT make knife scabbards out of it since it *can* corrode the metal that it comes in contact with.
If it's got plastic on one side, the Gods only know what it is, and has few uses in historical recreations anyway :) If it's got what appears to be a fabric pattern the flesh side, it may well be the skin of the sacred Nauga.
Ceallach You could try wetting a piece and then stamping or pressing a mark into it. If the mark has a crisp impression afterward, the leather is veg. If the impression is *just* discernable, it is chrome tanned. Also if its' a chalky white color, it is probably alum tanned. Chrome tanned, undyed leather is a pearl grey, faintly bluish tint.
Unofficial commercial note: Tandy carries two sorts of
tanning kits. One is a tanning paste, the other is a more
complete kit with lime for removing hair, etc.
There are also various companies that will tan hides and does a beautiful job at a very reasonable price. Some people who use them pay about 1/3 of what a commercial hide would cost.
If you have cleaned the skin well (no fat or meat) and have it salted the skin will last for a while. I have two hides in that condition that I have had for a year with no signs of deterioration.
Deterioration can be more subtle than outright petrification. Residual blood in the hide may set permanently, leaving blotches in the finished hide. Fat/oils oxidize, leaving discolorations. There are some organisms that can attack the salted hide, leaving various discolorations. Some of these things may not be as big a concern for someone making leather, but for parchment, I like to get my hands on the skins as soon as they're off the carcass. Unfortunately, that rarely happens. Even freezing, though better than salting for prolonged storage, can lead to problems in the long term.
Leatherworking in the Middle Ages - Period Leather. Copyright © 1996 Rick Cavasin, coded by I. Marc Carlson. This material is the exclusive property of the author, and as such should not be used with out his expressed permission.