A fabric finishing process that increases the lustre and smoothness of a plain weave cotton cloth. It was devised by the 19thC English inventor John Mercer, who found that treating the cloth to a caustic soda bath, followed by another in a neutralizing acid changed the surface texture, strengthening it, producing a stabilised shrinkage and a vastly improved capacity to hold dye fast.
Interestingly, a mercer is a historical term referring to a dealer in fine cloth and textiles.