Fibre‐surface Contaminants on Wool and Their Effect on Shrinkproofing

Normally processed wool fabric contains a small amount (about. 0.5–1%) of wax (shown by Täuber to be strongly adsorbed components of wool wax) which is removed by extraction with alcohols but. not by many other solvents. This wax contaminant affects resin adhesion, some shrinkproofing reactions, and dyeing rates. Ethanolic solutions of reducing agents and aqueous solutions of oxidising agents are able to shrinkproof unextracted fabric, despite the presence of residual wax. Their effectiveness is not due to removal of the natural contaminant during treatment. Small amounts of lubricant‐type surface contaminants, applied after mild chemical shrinkproofing treatments, restore the felting power of the treated wool. The effect appears to be due to modification of frictional properties by a lubricating action, although the restoration of the felting power occurs without alteration of the frictional coefficients measured by the capstan method. This raises doubts as to the relationship between such measurements and felting mechanism. More severe shrinkproofing treatments are generally unaffected by contaminants applied after treatment. Deliberately applied contaminants present before treatment can prevent the shrinkproofing reaction from occurring with both oxidising and reducing agents.