Cowhide rugs and cowhide are increasingly popular materials in both the fashion and home entertainment sectors and are renowned for their rugged natural appearance and sleek contemporary styling. These natural products have been used by man since time immemorial since humans first killed an animal for food and removed the skin to make clothing and shelter materials.
Numerous ways to make the hide more useful and durable than rawhide were discovered over the centuries, primarily by tanning the hide, which ensures that the hide will not break down permanently altering the protein nature of the hide. This process requires acidification of the skin and it is interesting to note that the Romans used human urine in the process and archaeological evidence has been found in Pompeii of urine collected from public baths just for this purpose.
There are mainly two forms of tanning processes, vegetable tanning and the more modern chrome tanning, first used commercially in 1856. The chrome tanning process produces a softer, higher quality cowhide. By being tanned with chromium salts, animal skins have a smoother and more uniform resulting texture.
This tanning method consists of the following steps:
1) Soak the skin
Raw cowhides are thoroughly washed before tanning, where dirt, dung, blood, and some preservatives such as sodium chloride and bactericides are initially applied and washed out of the hide.
2) Pickling the skin
Pickling dramatically increases the acidity of the hide to pH 3, allowing the chrome tanning salts to penetrate deep into the skin of the hide. Salts are also added to the pickling solution to prevent excessive swelling of the skin. This ensures that the skin lasts a long time and to help it can be preserved by adding up to 2% by weight of fungicides and bactericides.
3) Tan: Chrome tan
After pickling, which can take several days, the pH of the solution will gradually drop in acidity, which is when the chromium salts are added to the mix. To fix chromium in the skin, the pH is slowly increased by adding a chemical base that allows the chromium ions to cross-link with the free carboxyl groups on the collagen protein in the skin. This fixation process ensures that the leather is resistant to bacteria and high temperatures. When finished, a chrome tanned leather will contain approximately 2-3% dry weight Cr3+.
4) Basification
Chromium salts are fixed with magnesium oxide and an antifungal to ensure that the leather does not rot or mildew.
5) This penultimate step is done mechanically to ensure that the finished cowhide has the required thickness; this includes squeezing, splitting, and finally reducing.
6) Lastly, the leather is soaked with formate-baking soda and synthetic oils that make the final product smooth, subtle, and soft to the touch.