Abstract: The invention consists of a process to improve the resistance to stains on yarns, on the basis of wool, silk, polyamide, polyacrilonitrile, natural and artificial cellulosic fibres and in general, all other synthetical fibres which can be dyed. According to the invention the yarns are treated during the dyeing process with an aqueous solution containing up to 5% tannic acid in acid medium. It is economically advisable to add a stabiliser to the solution to avoid oxidation of the solution and the fibres, and possibly a wetting agent. Preferably the treatment is made during the dyeing procedure, before, during or after the effective dyeing step.

Abstract: The invention consists of a process to improve the resistance to stains on fibres, processed or not, finished or not on the basis of dyeable natural or synthetic fibres, in particular polyamide. According to the invention the fibres are treated with a solution containing tannic acid and a condensation product of a sulphonated phenol- or naphtol-derivate with an aldehyde. The treatment can be made before, during or after the dyeing process. The treatment is done in an acid medium.