Q. Illustrate Wood and Silica Flour?

Wood Flour: It is ground wood particles or other cellulose materials such as grain hulls. They serve the same purpose as cereals except that they do not increase green strength as much. When required, about 1% is added.

Silica Flour: It is very fine ground silica. It is generally mixed with about twice as much conventional moulding sand to make" facing sand" and is used to surround the pattern. It thus improves the surface finish of the casting, and because of its purity, it increases the hot strength of the mould face. It also resists metal penetration and minimizes sand expansion defects.