7. Sand preparation

The preparation of foundry sands involves the uniform distribution of binders and additives on the surface of the grains of base sand. It depends on several factors, the main ones being :

• the specific surface area of the base sand ;

• the ability of the base sand to be wetted by the binder ;

• binder viscosity.

It requires intensive mechanical work, as the uniformly built-up binder film is very thin - no more than 1 micrometer for every 1% of binder added. Moreover, non-uniform distribution can be a source of numerous defects.