A process for preparing cellulose ethers having delayed dissolution in water is described. The process comprises: (a) treating a moist cellulose ether with a solution comprising a dialdehyde; (b) adding an aqueous salt solution to the moist cellulose ether, such that said cellulose ether has a pH of from 6.0 to 8.0, the aqueous salt addition being performed at least one of, (i) prior to step (a), (ii) concurrently with step (a), and (iii) subsequent to step (a); and (c) drying and comminuting the treated cellulose ether of step (b). The cellulose ether, or mixtures of cellulose ethers, prepared by the method of the present invention may be used as protective colloids, thickeners and adhesives.