The invention relates to hardeners for water-based epoxy resin systems providing a longer resin pot life, incorporating particular compounds (F) and being obtainable by (i) reacting a mixture of (A) at least one epoxidized polyalkylene oxide (A), (B) at least one epoxidized aromatic hydroxy compound (B); (C) at least one aromatic hydroxy compound (C); and (D) optionally, at least one di- or tri-glycidyl ether compound (D), to form a first intermediate product (Z1) having an epoxy value of less than 10%; (ii) reacting the intermediate product (Z1) with a polyamine (E) to form a second intermediate product (Z2); and (iii) reacting the intermediate product (Z2) with a compound (F) selected from Lewis acids. The resin mixtures have pot lives in excess of one hour and, after curing, provide clear floor coatings with less than 3% shrinkage.