Abstract

A study has been made of the effect of heat applied before, during or after tensioning leather under controlled conditions to determine the cause and extent of stress relaxation which occurs in heat setting. The leathers examined were either full-chrome or chrome-retan, fatliquored to different extents with sperm oil or neatsfoot oil and tested after condition ing in the standard atmosphere or after mulling. The leathers had very similar physical properties, but the full-chrome leathers were more responsive than the chrome-retan leathers to the heat treatments. Fatliquoring was very important, but if the leathers were adequately lubricated, the effect of additional moisture was insignificantly small. The greatest effects regarding plastic and elastic properties of the leathers were brought about by the effect of heat while the leather was under tension. In this way, the extensibility at a given load, the deforma tion and the set of the leathers was increased. On the other hand, heating before tensioning, especially if the leathers were allowed to cool before applying the load, gave no improvement and in some cases inferior results.