Hide tanning methods: Pros and Cons
Since there was some heated discussion regarding my earlier post, I thought I might make a just-the-facts resource for new Vultures interested in tanning skins. Here’s some basic information about many different types of tans and what they’re good for:
PART I: Methods that preserve, but do not actually tan the hide
Rawhide: the hide is cured by drying (optionally with salt). This results in a hard, resilient material. Rawhide can be fur-on or fur-off, and is often used to preserve hides until they can be tanned or used (fur off) for finished goods such as drums, lacing, windows (historically), and can be rendered down into hide glue. Rawhide can be formed into shapes which will hold until they get wet. Once rehydrated, rawhide can be reshaped or tanned.
Pros: easy, lots of uses, nontoxic
Cons: rigid, easily damaged by beetles and other pests, susceptible to water
Borax: the hide is dried with the use of borax as a desiccant and preservative. The end result is a stiff skin, typically used fur-on (or feathers-on more commonly)
Pros: good for long-term preservation of bird specimens (eg. study skins)
Cons: skins can be damaged by beetles and other pests, susceptible to water
Misc “fatting” methods (unsmoked brain, egg, lard, oil, etc): fat is worked into the hide, opening up the fibres, “fluffing” them before drying. While drying, the hide is “broken”, stretched constantly in all directions untIl dry. If the hide is stretched well enough, the result is a soft, pliable skin. If not, the end result is oily rawhide. Some traditional cultures use variants of this method to produce a buckskin-like product, and it can be used with hair on hides (but see Cons)
Pros: nontoxic, beautiful white leather
Cons: difficult to learn, extremely labor intensive, easily damaged by beetles and other pests, will turn back into rawhide if any moisture gets into it
Battery acid tanning: the hide is immersed in (or painted with) an acid and salt mixture. This removes the minerals in the hide, leaving behind springy proteins (a la squishy skull). It is very difficult to neutralize the pH of battery acid tans, and many of them begin apart within a few years.
Cons: skins often end up hard, susceptible to water (reactivates the sulphuric acid which will eventually ruin the hide), short longevity, tanning bath is considered “hazardous waste” unless neutralized, contains unsafe traces of lead if acid is drained from a car battery
Other “pickle” tans: hides are soaked in mild acid (urine, vinegar, etc) of some sort and then left to dry or worked until dry. This method is part of the traditional preparation for fish skins, furs, but today is typically the precursor (”pickling” step) for other tans.
Pros: really easy, can make strong leather, nontoxic
Cons: skins often end up hard, easily damaged by beetles and other pests, susceptible to water (except tanned fish skins, which typically contain enough fat to resist water), urine-tanned leather shoes are notorious for breaking down faster than their vegetable- and chrome-tanned counterparts
PART II: Methods that tan the hide
Vegetable tanning: the hide is cured via tannins, often from tree bark, but sometimes other sources, such as tea. Generally used to make hair-off leather, but anecdotal evidence suggests it can be used to produce fur-on hides (though they will be stiff like leather)
Pros: easy, can be made from readily available materials (in which case it’s also cheap), nontoxic
Cons: time consuming (especially for thicker hides), will stain fur if tanned fur-on, need large quantities of plant material (minimum 2x weight of hide in dry bark), leather susceptible to water if not treated with wax/oil
Brain tanning: should really be called “smoke tanning”. The fat from the animal’s brain is rubbed into the hide, and then the hide is worked continuously until dry (as in the ‘fatting’ methods above). The soft, supple hide is then smoked over a low fire until the leather is tanned. Can be used for buckskin (most common) or fur-on hides.
Pros: nontoxic, cheap to free, very soft furs and leathers (if experienced)
Cons: difficult to learn, extremely labor intensive, smoke can stain fur with tar if prepared incorrectly, hides smell like smoke for some time after tanning
Alum tanning: the hide is preserved by a combination of salt and alum--historically, aluminum-potassium-phosphate, but aluminum sulphate is used today due to its availability. There has been some debate about the longevity of alum tans, but some examples from medieval times exist today. This method is best used for fur-on skins or garment-weight leather, as it makes a pliable, but not strong, leather. Traditionally, alum tans were used for ladies’ gloves, book covers, and royal furs.
Pros: relatively easy, soft furs and leathers, can be used for taxidermy
Cons: aluminum can irritate the skin of sensitive individuals, aluminum sulphate tans may result in disintegrating leather after decades
Chrome tanning: the hide is preserved with salt and chrome. This method is the most common tan used today, in everything from shoes to leather jackets to wallhanger furs to taxidermy. Most DIY tanning kits are chrome-based.
Pros: relatively easy, soft furs and leathers, can be used for taxidermy, superior water resistance
Cons: chrome can irritate the skin of sensitive individuals, tanning bath water is considered “hazardous waste” and must be disposed of accordingly
