Foundry moulds and cores

A process for the production of foundry moulds or cores which comprises,

• mixing granular refractory material with a binder, wherein said binder comprises (a) from 0.25% to 2.5% based on the weight of the refractory material of an aqueous solution of a potassium alkali phenol-formaldehyde resin, said aqueous solution having a solids content of from 50% to 75% and said resin having a weight average molecular weight (M.sub.w) of from 700 to 2000, a formaldehyde:phenol molar ratio of from 1.2:1 to 2.6:1 and a potassium hydroxide:phenol molar ratio of from 0.5:1 to 1.2:1, (b) from 0.05% to 3% based on the weight of said aqueous solution of at least one silane, and (c) from 20% to 110% based on the weight of said aqueous solution of at least one ester active to catalyze curing of said resin,
• discharging the mixture into a corebox or pattern mold, and allowing the resin to cure.