The processing of raw hides in the tannery industry involves several steps to transform animal hides into leather. Here's an overview of the basic process:
Preparation and Soaking
The raw hides are received from the slaughterhouse and typically still contain hair, flesh, and other impurities. The first step is to wash and soak the hides to remove these impurities. Soaking also rehydrates the hide, making it more pliable for further processing.
Liming, Deliming, and Bating
After soaking, the hides are treated with an alkaline solution, usually lime, to remove any remaining hair and epidermis (the outermost layer of the hide). This process also helps to open up the structure of the hide for easier penetration of tanning agents. Deliming involves the removal of excess lime, followed by bating, which uses enzymes or chemicals to further break down proteins and fibers in the hide. This step ensures that the hide is properly prepared for tanning.
Tanning
Tanning is the critical step where the hide is transformed into leather. Tanning agents, traditionally tannins from plant sources or modern synthetic tanning agents, are applied to the hide. These agents chemically bond to the collagen fibers in the hide, making it resistant to decay and providing the leather with its desirable characteristics.
Pickling and Neutralization
The tanned hide is adjusted to the desired pH level and treated with additional chemicals to stabilize the tanning process. After tanning, the leather is neutralized to remove excess tanning agents and adjust the pH level.
Dyeing and Fatliquoring
At this stage, the leather can be dyed to achieve the desired color. Fatliquoring involves the addition of oils and lubricants to make the leather soft, supple, and flexible.
Drying
The leather is carefully dried to remove excess moisture. This can be done using various methods, including air drying, vacuum drying, or heat drying.
Finishing
After drying, the leather may undergo various finishing processes to achieve the desired texture, appearance, and quality. This can include processes like embossing, sanding, and applying surface coatings.
Quality Control
Tanneries have strict quality control measures to ensure the final leather products meet the desired standards in terms of strength, appearance, and other properties.
The specific methods and chemicals used can vary depending on the type of leather being produced and the tannery's processes. It's essential for tanneries to adhere to environmental and safety regulations to minimize the impact of their operations on the environment and the health of their workers.