Abstract: Binders are described based on acid curing phenol resins and acid curing agents which, after mixing, have an extended processability time but nevertheless exhibit a rapid curing time at relatively low temperatures. They are obtained by using, as the resin, aqueous phenol resols and, as the curing agent, either copper, aluminum, or iron(III) salts of aromatic sulfonic acids or addition products of hydroxy-containing, water-compatible polyols with aromatic sulfonic acids or mixtures of these salts and the polyol addition products. The binders are used for impregnation of fabrics, for production of abrasives and for fiber reinforced plastics.