I'm just curious...I think I understand the properties of a "tanned" hide, but what exactly is a "cured" hide? Is it just that a "tanned" hide has better longevity than a "cured" hide, but the effects are temporarily the same? I was a cook before a taxidermist, and when I buy a "cured" ham, I still have to cook it. So does that mean that it's still raw? I just like to understand what I'm doing as I complete each step of the tanning process... call me a nerd. ;-)
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The terminology may be different in different parts of the country but I think of a cured hide as untanned and only fleshed and salted and dried out.
Glad you asked.
A fresh wet hide is about 68% water, and 29% structural protein. The rest is fat and non-structural proteins (keratin 1% to 2%, albumin and globulin). That keratin (hair & epidermis) percentage will of course vary with the type of hide.
The structure of a hide consists of collagen fiber bundles that are grouped together and interwoven with each other. The fibers form a network by continually branching off and tieing in with other perpendicular bundles. Each twisted fiber is made of "fibrils" that are rod like in appearance, and for reference would be about as big around as a pencil if blown up to one meter long.
When a raw hide dries, the fibers collapse onto each other and "glue" together, especially in the presence of heat. The hide becomes "brittle and horny", not useful for much except chew-toy.
What a tanning agent does is completely coat each individual fiber with a strongly bonded chemical veneer that prevents the fibers from being attacked by bacteria, and also keeps the fibers from gluing to each other when the hide dries. Picture it like a steel chicken wire fence. Uncoated it would rapidly rust away, but when galvanized the zinc coating protects the steel underneath.
Also, a tanned hide dries soft. Of course "soft" is a relative term and refers primarily to "when compared to a rawhide". Even saddle leather is then considered soft, and nearly all leathers can be made softer by breaking.
"Quality" of the tan is often measured by the persistence of the bond. How well and how long does the chemical coating on the fibers last, and will it stay bonded while the leather is washed, dyed, heated, worn, etc.
In fact, one of the very basic requirements for a skin to be defined as "leather" is that the skin will not revert to raw or cured when wet.
"Curing" on the other hand refers to a less permanent condition of chemical treatment or drying wherein the only goal is to prevent rotting. No bonded chemical coating of the protein fibers has occured, the skin is not soft and cannot be made soft by normal breaking, and when wet the skin quickly reverts to raw condition.
Curing is a short-term preservation step taken to prevent putrefaction until a skin can be tanned.
For examples, dry preservative is not a tanning agent, and DPed skins are cured, not tanned. Aluminum sulphate is a tanning agent, but can be washed out by vigorous repeated washings, especially at higher temperatures. For this reason, in the old days alum tanning was called "tawing" and the skins were not suitable for the high temp dyes that were used. For fur dressing and taxidermy tanning, alum works well as an excellent hair setter and full bodied (producing a plump skin) tanning agent.
Syntans, such as EZE-100, Kwik-N-Eze, Liqua-Tan, Paratan, Arrowhead Crystal, and others (I don't mean to leave any out)are very persistent and aggressively bonding agents that produce a thin, empty leather that can be thoroughly and repeatedly washed. Thin and empty = low shrink, making them an excellent choice for taxidermy.
Other cures used for mounting by taxidermists would include pickle and oil, denatured alcohol soak (which does impart some formaldehyde tanning), and various other chemical treatments available that prevent bacterial damage until the skin can be mounted and dried. Cured hides for mounting must be handled carefully to avoid heating and hair loss, mounted quickly, and protected from humidity.
Hope that helps!
I really appreciate your knowledge on this. I feel like I now have an understanding of what I'm actually doing. Thanks for taking the time.
steve thanks for taking the time to type that all! was impressive, and i appreciate the time it took