PRIOR to the advent of the electrolytic method, the art of waterproofing textile fabrics was confined to two methods : -Mechanical processes and chemical processes .
Mechanical processes embrace all methods which involve direct impregnation, filling or coating the fabrics with rubber, waxes and various compounds which achieve the result of rendering them proof against the pene'ration of both water and air . In view of the fact that the vast majority of the uses for which textile fabrics arc designed requires that they possess the quality of ventilation, all of these mechanical processes are correlatively restricted in their application and are employed most large!-in association with fabrics intended for specific uses wherein air circulation is a negligible factor ; when used in associations where ventilation is an essential factor, notably for wearing apparel such as raincoats, the results are unsatisfactory from the viewpoints of both comfort and hygiene .
Chemical processes embrace all methods whereby a coating of a water-repelling substance is deposited on the surfaces, yarns or fibres of textile fabrics through the media of chemical reactions . 'This process is covered by li. S . Patent, No, 933,861, issued September 14, 1909, and by several other patents issued subsequently .