Abstract

Since the time of Henry Procter, there have been important developments in early stage processing of hides and skins but there have been no fundamental changes in the process. The developments have mainly been the result of economic and environmental pressures to reduce labour requirements and processing times and to meet environmental regulations. The major unhairing developments have been the rapid hairdestroying drum processes and the subsequent rapid hair-saving systems. The promise of enzymes, amines and other systems for unhairing has not yet been fulfilled. Despite enormous research effort, most unhairing and dewooling processes still use lime and suiphides. It can be argued that unhairing is now the least environmentally acceptable tannery process. Although the adoption of one of the several rapid hair-saving processes now available significantly reduces effluent loads, a better, cleaner system for unhairing is still needed. Ideally, the hair should be recovered in a fibrous form in a sulphide-free process. Unless handled appropriately, sulphides create toxicity, odour and effluent problems. Exposure standards for gases and vapours in the occupational environment and industrial odour emission limits, incorporating plume modelling, are being enforced. Unhairing systems must be effective on all hides and skins irrespective of breed, age, sex, nutrition and season. Skin and hair structure and depilation processes and their environmental effects are reviewed.