The present invention relates to a process to improve the organoleptic behaviour and the physical characteristics of leather by the use of aqueous solutions of copolymers of 90 to 20%-wt acrylic acid or methyacrylic acid, as well as 10 to 80%-wt of a monomer of the formula ##STR1## wherein R.sub.1 is hydrogen or methyl; R.sub.2 and R.sub.3, which are equal or different, are methyl or ethyl; x stands for an optionally branched alkylene radical with 1 to 5 carbon atoms; the amine nitrogen is optionally neutralized or quaternized; and the molecular weight of the copolymer, measured at a pH of 8.0, is less than 100,000. The concentration of the copolymer in the aqueous solution is 0.02 to 10%-wt, relative to the shaved weight of the leather.