Use of an acid-containing sizing composition in the foundry industry

The present invention describes the use of a sizing composition comprising an aqueous phase having a pH of at most 5 and one or more refractory materials, in the foundry industry as well as sized, water glass-bonded foundry moldings, in particular foundry molds and / or cores, each of which comprises such an aforementioned sizing composition , Further, the invention describes a method of producing a sized, water glass bonded foundry mold body. The invention also describes a kit, including containing an aforementioned sizing composition comprising an aqueous acid and one or more refractory materials.