Tannins, a diverse group of organic compounds found in nearly all plants, serve to protect plants from certain diseases and prevent decomposition. These preservative properties were discovered a millenia ago, as humans searched for ways to treat animal hides and make them pliable, durable, and most importantly, wearable. Tannic acid, one of the first of these tannins to be exploited in such a way, is present in especially high quantities in oak bark, and to a lesser degree, acorns. Extracting usable tannic acid from acorns provides an ecologically-friendly way to treat hides without using commercial chemicals or damaging trees.
Things You'll Need
Animal hide, skinned and stretched, scraped
Acorns (1-2 pounds for a small hide)
Container (large enough to immerse your hide)
Scraper or sawblade
Sawhorse or large log
Place acorns in the large pot and fill with water. Boil the acorns until the water is dark brown - several hours. Replace water as necessary. If you need more solution, repeat this step. When satisfied with the color and amount of the solution, remove the acorns and allow the solution to cool.
Fill your large container with baking soda and water. Use at least two tablespoons of baking soda per liter of water (seven to eight tablespoons per gallon).
Soak your hide in the baking soda-water solution. This will raise the pH of the collagen in the hide, making it more ready to accept the tannic acid, as well as loosening remaining undesirable material and preparing the hide for scudding (see step 8).
Dump out the baking soda solution and rinse the bucket.
Press the hide to remove excess water. Do not wring it, as this may damage the hide.
Scud your hide. "Scudding" refers to the final stage of cleaning before the tanning solution is applied. Using your scraping implement (or the toothless side of your saw blade), remove any muscle fibers, capillaries or other tissue that remained on the hide after scraping. If you wish to have a hairless hide, use your implement to scrape the hairy side as well.
Add the tannic acid from the pot to the large container. The solution should completely cover the hide. The tannic acid may be diluted as necessary, remembering that the darker the color, the stronger the solution and the more quickly it will take effect.
Let the hide rest in the tanning solution for two to five days, depending on the size of the hide and thickness of the skin.
Repeat step nine with a stronger (darker) solution, if desired, to attain a more supple hide.
Hang the hide over the sawhorse to air-dry. Shift the hide often so that it dries evenly.
Work the hide. Before it is completely dry, tug and pull it over the sawhorse to make it more supple. Tannic acid has an astringent quality that pulls the hide together, and this process helps to counteract that effect somewhat in order to keep the skin supple. Work it evenly and repeat often.
Finish the hide according to your preference.
The astringent property of the tannic acid may make large hides difficult to handle unless they are stretched. To accomplish this, you can make a simple square rack from two-by-four foot boards, and attach the hide by threading a thin cord at 1-inch intervals around the entire hide. Pull the cord tight to keep the hide stretched. If possible, immerse the entire rack in the tanning solution.
Tannic acid will dye fur dark brown. To avoid darkening lighter-colored furs, you can apply the tannic acid to the skin side only instead of immersing the fur. Apply liberally to only that side and repeat often.