Materials for Core Making:

Casting procedure is unique in their ability to incorporate internal cavities or reentrant sections with relative easiness. In order to produce these features, though, it is frequently necessary to use cores as part of the mould. When these cores constitute an added price, they do much to expand the capabilities of the procedure, and good design practice can frequently facilitate and simplify their use.

For cores natural sand having small percentages of clay might be used however synthetic sand is preferred. In dried condition Green sand cores can also be utilized, with the bonding agents like cereals and linseed oil. The fundamental advantage of organic binders as compared to clay is that they break down under the influence of the heat and may easily be eliminated from the castings at shakeout. It is very significant that proper baking times and temperatures be established for the several binders and for several in core size. A correctly baked core does not generate harmful gases, has sufficient strength and collapse at the right time after metal is poured around it.

Lately, plastics have begun to supplement linseed oil like core binder. Urea formaldehyde and phenol formaldehyde are the two most broadly used. Urea formaldehyde breaks down at extremely low temperature as compared to linseed oil or phenol, so it is utilized in the low melting metals. In core making a still more recent development is sodium silicate-CO₂