Natural Sillimanite as a Glass Refractory Material

JSGT 1923 V07 T258-T3

MR. E. A. COAD PRYOR asked if Mr. English would tell them how much grog there was in the clay used in the tests described?
MR. ENGLISH replied that a standard clay mixture was used of which he had not precise knowledge, but thought the percentage of grog was about a third.

By S English