Method for manufacturing foundry cores

A method of preparing a foundry core which comprises the steps of mixing with a neutral or acidic core sand an aromatic or aliphatic sulfonic acid and a metal compound reactable at substantially ambient temperature with said sulfonic acid to form a latent metal sulfonate catalyst for curable binders and then mixing with the treated core sand a curable binder, forming said treated core sand and binder into a desired shape and heating to cure said binder to produce said sand core.