Phosphate investment compositions and methods of use thereof

A method of molding comprising the following steps:

• (i) creating a wax model of an object to be reproduced;
• (ii) attaching the wax model to a “sprue pin” that, in turn, is positioned on a base;
• (iii) placing a hollow cylindrical ring of metal, plastic, or paper on the base to form a cylindrical cavity;
• (iv) mixing an investment powder with water, aqueous silica sol, or other liquid, to create a slurry, wherein said powder comprises silica filler in an amount ranging from 72% w/w to 80% w/w mono-ammonium phosphate in an amount ranging from 10% w/w to 17% w/w and magnesium oxide in an amount ranging from 7% w/w to 15% w/w, wherein 15-25% of silica filler has a size of over 45 microns and no more than 0.2% of silica filler has a size of over 212 microns;
• (v) filling the cylindrical cavity by pouring the slurry over the wax model and the sprue pin;
• (vi) allowing the slurry to set, thereby forming a mold intermediate that comprises the wax model, sprue pin, and overlying set investment;
• (vii) removing the base and placing the mold intermediate while still wet into a burn out furnace that has been preheated to at least 700° C. to make a finished mold;
• (viii) filling the mold with metal, glass porcelain or other ceramic which has been heated until it is fluid;
• and
• (ix) cooling the mold and removing the finished casting.