The Tanyard Processes

Either during or after the deliming process, the leather is treated with enzymes to impart softness, stretch, and flexibility in a process called baiting. Pickling is done by treating the hide with a solution of brine and sulfuric acid, and is the last step before the actual tanning process begins.

Vegetable Tanning

The oldest if not the original tanning method is Vegetable Tanning. Hides are treated with the barks of trees that contain the naturally occurring element Tannin, from which the term “tanning” originates.

The skins are stretched onto frames and immersed into a series of vats containing higher and higher concentrations of tannin, until the tanning material penetrates to the center of the hide. This process of Vegetable Tanning takes about three weeks, as opposed to the Mineral Tanning process that can be done in a day.

Vegetable tanned leather is stiff yet pliable and is used for leather shoes, belts, bags, and luggage.

Mineral Tanning

The Mineral Tanning process makes use of chemicals, most notably chromium sulfate, and is sometimes referred to as chrome tanning. Pickled hides with a pH of 3 are immersed in a bath to which the chrome tanning materials are introduced to raise the pH.

Chrome tanned leather is soft and pliable, and is the most used method for treating the skins of cattle, pigs, goat and lamb. It produces a flexible, stretchable leather that is suitable for garments, and of course, leather motorcycle apparel.

After the tanning cycle is complete, hides will be graded for quality, split into flesh (bottom) and grain (top) layers, and then shaved to their desired thickness.

More typical with chrome than vegetable tanning, the grain leathers will then go through a retanning process. The leather will then be dyed, usually with an aniline based dye that permeates the skin to the center.

The last step before drying is fatliquoring, a process where oils are introduced to the leather to replace those lost in the Beamhouse and Tanyard processes.

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Originally posted 2009-07-02 07:57:46.