Abstract: The dimensional stability, crease retention, wrinkle resistance and smooth drying characteristics of a cellulose fiber-containing material such as a cotton fabric are improved by impregnating the material with an aqueous formaldehyde phase and curing the formaldehyde-containing material at high temperature in the presence of catalyst-forming sulfur dioxide while governing the amount of water in the system to provide a self-limiting reaction system, water being the limiting factor in the reaction by which an acid curing catalyst is formed from formaldehyde, sulfur dioxide and water. The aqueous formaldehyde phase may be applied to the material as such, or it may be formed in the material by exposing the latter in a humidified state to formaldehyde vapor. Sulfur dioxide may be introduced into the system either in the course of the aqueous impregnation step or in the curing step.