Introduction to Tanning

Introduction - Tanneries

Tanneries - Leather processing industries where animal hides are processed and tanned to form leather.

Leather – The final product from tanneries made from animal hides and is used for making shoes, upholstery, clothing, gloves, hats, books, handbags, etc.

Tanning – The process of treating animal skins to make them durable & less susceptible to decomposition. Derived from word ‘tannin' – an acidic compound used for tanning previously.

Leather-processing

•   The leather manufacturing process is divided into three sub-processes:

Tanning Process

Depending on the tanning agent used, this process may involve the following

Vegetable Tanning – Employs ‘tannin'. The tannins (a class of polyphenol astringent chemical) occur in the plant bark and leaves. Tannins bind to the collagen proteins in the hide causing them to become less water-soluble, and more bacterial-resistant. The process also causes the hide to become more flexible.

Mineral Tanning/ Chrome Tanning – Chromium compounds are used to penetrate the hides and complex with collagen to form interlinked structures.

Chromium(III) sulfate  [Cr(H₂O)₆]₂(SO₄)₃ is the used mostly.

Tanning is faster w.r.t. vegetable tannins.

The chromium-tanned hide contains about 2-3% dry weight percent of Cr³⁺.

 

Vegetable Tanning

Chrome Tanning