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Green Sand Metalcasting Foundry News

"T" - Glossary of Foundry Additives (Including Core Oils)

Posted by Hill and Griffith Company on Aug 7, 2018 4:21:00 PM

T - Foundry Additives Glossary

Talc is a hydrated magnesium silicate with the composition [4SiO2 3MgO • H2O]. It is a soft, friable mineral having an oily touch. It has a Moh's hardness of 1 and a specific gravity of 2.8. It is referred to as "soapstone." It is used as a parting compound when impregnated with wax and ground. It has been used in nonferrous mold coatings, ladle refractory coatings, and when blended with clay, bentonite, cereal or dextrin, it is used as a core paste. It is used as an additive in various core compounds and core fillers.

Is prepared from extraction of the liquid squeezed from wetted oak bark. It is rarely, but sometimes used as an auxiliary binder in core sand mixtures where clay is present.  


Tar is a residue from the distillation of coal and petroleum. Various types of coal yield different qualities and quantities of tars. Tar may be rich in benzene, toluene, naphthalene or other aromatic compounds. The specific gravity of the average tar in the dry state is about 1.2. Coal tars used in the foundry industry are often referred to as "pitch." Coal tar pitch is a most stable bituminous form of carbon. It is ground and sold to the foundry industry principally as a binder for dry sand molding, or as an ingredient to dry sand core compounds. Tar is generally defined as a thick, heavy, dark brown or black liquid obtained from the distillation of wood, coal, peat, petroleum or other organic materials. The chemical composition of a tar varies with the temperature at which it is recovered and from the raw material from which it is obtained. Tar used in foundry molding sands prior to 1910 was obtained from the distillation of wood. Later, tar obtained from the distillation of coal was accepted. After 1930, tar was also obtained and accepted from the distillation of petroleum. One of the past principal foundry uses of tar was the swabbing of chills, which has since been declining. Tar, diluted with kerosene or fuel oil has also been used as a spray for green sand mold surfaces to improve casting finish. The addition of one-half percent to one percent of tar into molding sands containing pitch is used by some foundries. Tar helps soften the pitch and improves the green sand toughness.


Is used to lubricate molding or core sand mixtures. It is used to give molding or core sand mixtures proper workability. Temper water is used to develop plasticity in clay bonds so as to enable the mixtures to form shapes and designs. Temper water should not be used excessively.

A popular naturally bonded sand having various grades of fine­ness, clay content and properties that are used in many southern foun­dries. There are several producers of these naturally clay bonded Tennessee Sands.

If heat is required for setting, these binders are called, "thermal setting binders," whether they are oil base, resin, or compounds.

Hot box and cold box resins which require heat to complete their curing in sand mixtures are generally referred to by this classification.

A material made into a plastic mass and formed into shape by the application of heat. It becomes plastic again when it is reheated.



Toluene is often called "toluol" or "methyl-benzene." It has the chemical composition of [C6H5CH3]. It is obtained from coal tar and coal tar distillates. It has a specific gravity of 0.87. It is flammable and is the liquid carrier used in many light-off mold sprays, light-off coatings, and some liquid partings. It has a boiling point of 230° F. (ll0 °C.).

Is used for no-bake sand mixtures.

Tragacanth Gum is a secretion from a vegetable or a tree shrub. It is used in adhesives and as an emulsifying agent. It is soluble in alkaline solutions, it swells in water, and is insoluble in alcohol. It is used in many foundry compounds, mold castings, refractory washes and solutions. Other less expensive resins and gums are being sub­stituted. It is prominently used in the ceramic industry in glazes, coatings, and clay bodies as an auxiliary binder.

It is an infusorial diatomaceous earth. It is a variety of opal. It is not widely used in the foundry industry, but is used as a non-silica parting compound when it is treated with oils and waxes to make it water repellent. It is ground and screened, then sold for use as a dry parting compound.

A natural, commercial (trademarked) "Vinsol" resin. It is an alcohol soluble resin and has a higher melting point than many resins. It is not soluble in gasoline. It is a favorite for use in the steel found­ries, as well as for a binder in heavy core sand assemblies. Its binding action occurs as the rosin melts from the oven baking temperature, or from the heat penetration of the casting into the core or mold. It may be used as an ingredient of core oil. It is used often with glutrin, goulac, or dextrin in order to add waterproof qualities to the sand mixtures, since these binders are generally hygroscopic.

Is one of the most powerful drying oils known. It has almost double the rapidity of drying power as linseed oil. It is one of the first oils substituted for linseed oil by commercial core oil producers. Tung oil was first pressed from seeds of a plant growing extensively in Asia, particularly China and Japan. Because of this, it became known as "China Wood Oil." The nuts contain over 50% of oil when they are pressed. Its odor resembles that of heated bacon fat. Tung oil has a specific gravity between 0.94 to 0.943. It has a uniform drying rate and does not form a skin as does linseed oil. It worked very well from the time of its introduction in commercial core oils. Rosin in the core oils has a great affinity for it. Many commercial foundry grades of core oil contain both linseed and tung oil but economics is the final determination. There are now many trees being raised in the southern part of the U.S.A. from which tung oil is pro­duced. The U.S.A. trees do not compare to the percentage of oil re­turned by the Asian trees.

An oil obtained by steam distillation of the oleoresin which ex­udes when various conifer trees are cut. It varies in properties from the different trees from which it is extracted. It is used in many com­mercial foundry coatings to add, or supply, special properties.


Review of "Glossary of Foundry Additives" by Clyde A. Sanders, American Colloid Company

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