G - Foundry Additives Glossary
GANISTER (See: SILICA)
Ganister is a quartzite, a ceramic aggregate, used principally as a foundry refractory. The melting point is usually in excess of 3056 ° F. (1680 ° C.) when selected for foundry purposes. It is sold as a foundry sand when the fines are screened and produced during the reduction and grading of the ganister.
GELATIN (See: GLUE-GUMS)
A form of animal jelly. A glutinous material such as glue from animal tissue which is used in core compounds and core pastes or glues. Gelatin is also used to a minor degree in certain core sand mixtures and core washes as a thickener.
GELATINIZED STARCH (See: CEREAL-CORE BINDER-STARCH)
A white, odorless, powdery carbohydrate [(C6H10O5)x] which is widely disseminated amongst plants and grains. It requires processing to further gelatinize it. It is used as a binder in the foundry for molds or core compounds.
GILSONITE (See: ASPHALT-PITCH) Gilsonite is a natural asphalt found commercially in Colorado and Utah. In nature, it appears as a black, lustrous, brittle mass, and has a specific gravity of about 1.07. It is used extensively in bituminous waterproof paints and in japans, not common to the foundry. It is further used in roofing, paving, and hard rubber insulations, but the foundry has recognized its basic inherent properties as valuable for use in molding sands under certain circumstances. Other large natural asphalt deposits are found in Oklahoma and are 'referred to as "Grahamite." The mineral names, "Elaterite" and "Wurtzilite" are forms of gilsonite and are found in sections of Utah. Imported supplies of asphalts from Trinidad are called "Manjak."
General Foundry Use
As little as 0.5 lb. of gilsonite is added to every 100 lbs. of molding sand, when gilsonite replaces 5% by weight seacoal additions. Many foundries exceed this amount, particularly as an addition to molds for larger or heavier castings, such as those molds used for casting lathe beds, motor blocks, base rails, road equipment castings, carriage frames, gray iron rolls, and the like. Foundries producing light to medium weight castings in green molding sand, employ gilsonite in the ratio of 1 part gilsonite to 30 parts of molding sand. This, of course, may be high, but when evidence of increased dry and hot compression strengths are noted, the gilsonite is reduced and the ratio of 1 part gilsonite to 65 parts molding sand is used, or until the baked out hot strengths become normal. 0.25% by weight addition of gilsonite produces the same facing value as 4% to 5% by weight seacoal in many green sand mixtures.