Gerbung

Gerbung is the process in leather production by which hides or skins are treated with tanning agents to convert them into durable, less water-sensitive leather. The tanning cross-links collagen fibers in the dermis, stabilizing the protein structure and making the material resistant to microbial decay and shrinkage.

Historically, vegetable tanning, using tannins from tree bark and other plant sources, is the oldest method and remains valued for producing firm, stiff leather often used in saddlery, belts, and leather goods. Chrome tanning, which uses chromium salts such as chromium(III) sulfate, became dominant in the 19th and 20th centuries. It is faster, more flexible, and yields uniform color, making it common for footwear, upholstery, and general leather products. Other methods include aldehyde or synthetic tanning, and oil or combination retanning to modify properties.

Typical process steps include preparatory treatments (liming, dehairing, and bleaching), bating and deliming to soften the material, and pH adjustment (pickling) before the actual tanning. Vegetable-tanned leathers require extended immersion in tannin baths over weeks, while chrome-tanned leather undergoes rapid tanning in hours to days. After tanning, retanning, fatliquoring (softening with oils), dyeing, and finishing are conducted, followed by drying and conditioning.

Environmental and economic considerations vary by method. Chrome tanning raises concerns about chromium waste, prompting regulatory controls and cleaner technologies, whereas vegetable tanning is often viewed as more natural but slower and resource-intensive. Gerbung together with finishing determines the final use and quality of the leather.