The effect after thermal ageing of reduction of aldehyde carbonyl groups in cotton textiles is described. Since acidic degradation products are largely removed by washing subsequent deterioration must originate from oxidation of these groups. Removing them would contribute to long-term stability. Sodium borohydride and tetramethylammonium tetrahydroborate were used as reducing agents. Details are given of sample preparation ageing conditions and mechanical testing (tensile and tear). It was found that reduction did improve both colour and strength retention. Results are expressed in tables and graphs. References.