From hide to leather
The process of making leather might seem fairly straightforward once you know about the procedure itself, but what really happens to the hide during these steps? To fully understand, we need to look at the nature of what constitutes a hide. When we speak about a hide for traditional leather, we are talking about the hide or skin of an animal (that also makes fish leather an option, while the process is slightly different).
Each hide or skin consists of three layers. The epidermis is the thin outer layer that protects animals from water-loss. In essence, the epidermis holds water in the skin. The Corium (i.e., dermis) is the central layer, and a fat layer is below this. As you might have guessed from its name, the corium is used to create leather. During the leather making process, unnecessary substances are removed from the corium and, the protein structure of the collagen is altered. Only about 85% of the protein is collagen, so all the rest must go.
This protein removal is why the beamhouse process is so important. During the soaking operation, acids, salts, enzymes, and tannins are used to dissolve fats and remove other elements, which gradually changes the protein structure. The fresh hide contains approximately 60/70% water by weight, which is removed. Raw hide is an exception to the soaking operation, as only water content is removed. Removal of water from the hide and alteration of the dermis protein structure can be achieved using various methods, each with different benefits and results. Traditional methods, such as vegetable tanning and brain tanning, closely emulate the natural, slow tanning process by using natural tanning agents which affect the dermis.
Meeting modern-day demands for leather, however, requires processes which move slightly faster. The use of chemicals in the modern process helps the process speed-up. Chemicals used are today often bio- or water-based, making them both effective and environmentally friendly.