Abstract

Silicone waterproofed upper leather loses much of its waterproofness in wear. Various possible explanations of the loss of were examined experimentally. The following are not the main causes of the loss : —loss of silicone; redistribution of silicone, whether between layers in the leather or by rolling up of surface films on the fibres; the exposure of fresh, hydrophilic fibre surfaces; changes of mechanical properties of the footwear as a whole, or of the upper leathers in particular. Salts present in the leather, however, cause a drastic reduction of waterproofness such as occurs in actual wear, and since salts are certainly present in the worn uppers (derived from perspiration and other sources) they may be the main cause of their loss of waterproofness. Removal of the salts renews the waterproofness of silicone treated leather, and their action is thought to depend merely upon their hydrophilic properties.