First Phase of Leather Goods Manufacture: Skinning & Curing
The first stage in the leather goods manufacture process is skinning and curing. Skinning is the process of obtaining the animal skin for leather working. The skin must be removed from the animal after it has been killed, and also before the heat dissipates from the tissue.
After this, the Curing process begins. Curing is done with salt, and this prevents the skin from decomposing between the time that it is obtained and the time that it is finally processed. It does this by removing any fluids or water from the skins, thereby preventing any bacteria from growing.
The processes in the middle stage between curing and tanning are grouped together under the category of beamhouse operations. This involves soaking, liming, removing unwanted tissues, deliming, bating, drenching and pickling.
Firstly, the skins are soaked in clean water to remove any leftover salt from the curing process. Next, liming breaks down the hair on the skin and removes natural greases and fats. De-hairing is done with chemicals, as well as manually removed. After this, deliming is done to bring down the pH level of the collagen in the skin so that enzymes can work to soften the skin. The process of using enzymes to soften the skin is called bating. Finally, the process of pickling is done where the skins are treated with salt and sulfuric acid, to prepare it for the final stage of tanning.
Tanning is the final process of turning the skin and hides into leather. This process changes the structure of protein contained in the skin, permanently. There are two main methods of tanning: mineral methods and vegetable methods.
Vegetable tanning uses chemicals known as tannins which occur naturally in the leaves and bark of trees or plants. Mineral methods involve using chrome.