Abstract

In wet countries, the curing of raw woolskins is carried out by salting however, this method causes problems to the tanners given the high salt content in the soaking effluents. In order to avoid this salinity problem, the curing of woolskins by drying is preferred. But in countries where climatic conditions are not adequate, hot air drying can be used, which may cause irreversible damage to the skins. In this paper, laboratory drying trials on raw woolskin at different temperatures are reported to demonstrate the damage arising from inadequate drying conditions. In addition, some recommendations on the most suitable drying conditions are offered. Briefly, drying must be carried out under the following conditions:

• Well stretched out skins with the flesh side outwards
• Gentle air flow, at no more than 20°C, at low relative humidity

These conditions which are rarely supplied by the climate in many countries can be easily achieved by means of a heat pump dryer. The results of a semi-industrial drying trial on raw woolskin in a pilot plant operated by a heat pump are reported. Satisfactory drying was achieved in 20 hours using air at a temperature between 28—22°C and a relative humidity of 30—40%.