Modern techniques of castings production, including moulding sands production, require a strict technological regime and high quality

materials. In the case of self-hardening moulding sands with synthetic binders those requirements apply mainly to sand, which adds to

more than 98% of the whole moulding sand mixture. The factors that affect the quality of the moulding sands are both chemical (SiO2

,

Fe2O3 and carbonates content) and physical. Among these factors somewhat less attention is paid to the granulometric composition of the

sands. As a part of this study, the effect of sand quality on bending strength Rgu

and thermal deformation of self-hardening moulding sands

with furfural and alkyd resin was assessed. Moulding sands with furfural resin are known [1] to be the most susceptible to the sand quality.

A negative effect on its properties has, among others, high content of clay binder and so-called subgrains (fraction smaller than 0,1mm),

which can lead to neutralization of acidic hardeners (in the case of moulding sands with furfuryl resin) and also increase the specific

surface, what forces greater amount of binding agents. The research used 5 different quartz sands originating from different sources and

characterized with different grain composition and different clay binder content.