Bating and Pickling
Hides are treated with enzymes, similar to those found in the digestive system, to break down proteins. As a result the hides become softer. The duration of the bating process depends largely on the desired softness of the leather being produced. The softer the leather required, the longer the bating process.
Bird droppings and dog faeces have were known to have been used for this procedure prior to the development of industrially-produced chemicals. In areas where enough human urine could be collected, urine was used instead of bird and dog feces. Urine played an important role in the history of leather production. The natural enzymes and ammonia in urine helped soften the leather and break down the fibers, allowing tanners to better prepare the leather for the actual tanning process. During soaking, the leather was immersed in a mixture of urine, water, and other substances such as salt. In the past, urine was a valuable resource for leather production. In some cultures, special collection sites were set up to gather sufficient quantities of urine. Collectors often held a special status as their contribution to the leather industry was of great importance.
With the development of chemistry in the 18th and 19th centuries, alternative methods and chemical substances were introduced that were more efficient and reproducible than urine, dog or bird feces. This led to a decline in the use of urine in leather production. Nowadays, such substances are no longer used in leather production.
This process makes the fibres of the hides more receptive to tanning. Pickling increases the acidity of the hide to a pH of 3, enabling chromium tannins to enter the hide. Salts are added to prevent the fibres from swelling. For preservation purposes, fungicides and bactericides are used.
Old tanners tell of how long ago tanners tested the pH of pickled hides by biting on a piece of hide, which over time started dissolving the front teeth. Nevertheless, many tanners initially found it difficult to trust ph test paper or liquid indicators, which then prevailed.
Videos about the leather production
|Process steps in the leather production
|storage - soaking - liming - fleshing - splitting - pickling - tanning - neutralising - withering - sorting - shaving - dyeing - fatliquoring - retanning - drying - finish - softening - final check
|Chrome tanning - Vegetable-tanned leather - Synthetic tanning - Tanning with fats and oils