Foundry coatings can be thought of as paints especially developed for the metal casting industry. The difference between conventional paints and a foundry coating is that the foundry coating is designed to withstand the high temperatures of molten metal and to act as a barrier between molten metal and a core or mould surface. Foundry coatings are also referred to as washes.

All foundry coatings are suspensions of a high temperature mineral or refractory in a liquid carrier. After being applied to a core or mould surface the liquid is removed by evaporation and a layer of refractory is left on the sand surface. This layer or barrier can prevent or minimize the penetration of molten metal into the sand, can reduce or prevent “burn-on” and erosion of the sand and generally improves the quality of a casting surface. The benefits of a foundry coating are only achieved if the coating is the proper one for the job and if the coating is correctly prepared, applied, and dried. Improperly selected, prepared or applied coatings can result in poor casting finish and / or applied coating defects such as scabs, blows, gas holes, inclusions, etc.