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Green Sand Metalcasting Foundry News

"B" - Glossary of Foundry Additives

Posted by Hill and Griffith Company on Dec 5, 2017 3:07:16 PM

B - Foundry Additives Glossary

Is the residue left after grinding sugar cane and extracting the juice. The shredded fibers are largely used as a fuel, but it has found various uses as a cellulose material in the foundry sand mixtures. Bagasse has been substituted for wood flour and other cellulose addi­tives, but it is hygroscopic, and many foundries have frowned upon its use, It is most difficult to produce bagasse in a commercial form so as to economically prepare it for the foundry market. Unless a foundry is near a ready source of bagasse, the economics make it practically prohibitive to compete against commercially accepted cellulose additives.

There are a wide range of compositions, and a great number of ball clays are available for foundry use. The silica content [SiO2] is approximately 40% to 60%; the alumina [ Al2O3] is approximately 25 % to 40%. Most foundries use fireclay rather than ball clay as a bonding agent, even though the clay mineral of each is a "disordered" form of the mineral, "Kaolinite." Fireclays are also more com­mercially and economically usable. Ball clays contain a considerable proportion of organic matter and this should be of interest to the user. Ball clays owe their name to their original form when mined, as they were generally plastic and were rolled into balls as they were dug. They are very fine grained in structure and are quite plastic. They are sedimentary deposited clays and are considered more plastic than fireclay when used as a foundry sand bond.


A commercial grade of silica sand. It is finer than the average sand deposit and used both as a base sand, as well as an additive to coarser base sands. Banding sand is more commonly used in the glass industry.

A deposit of sand in specific stratas and locations, deriving this name from the banks of deposit. It is used in fine sand mixtures. BAUXITE (See: ALUMINA-ALUMINUM OXIDE-CLAYS CORUNDUM-FIRECLAY) Is a form of clay having the chemical composition [ Al203 2H20]. Little bauxite is used, as mined, in the foundry. Alumina (Al203) is a product made from bauxite which is an excellent foundry refractory. It is also the source of the metal, aluminum, when the bauxite is processed or the metal is extracted.

This wax is formed and deposited by the honey bee. The bees build combs, which are a deposited wax compound, to receive the honey. After extraction of the honey for commercial purposes, the wax from the combs is commercially melted and molded into cakes. Its specific gravity is about 0.965 to 0.969 and its melting point is about 140°F. (63°C.). Beeswax has found its place in certain liquid parting and as a commercial replacement where paraffins, stearine, Japan wax and other vegetable waxes are used. Many foundry liquid partings and core compounds use, or have used, beeswax. It is used for various foundry purposes as fillers in the pattern shop and elsewhere. Beeswax is also used to form patterns in the "Lost Wax Process" of molding.

The most colloidal of all clays is bentonite. It was derived from the chemical action of sea water on volcanic ash over millions of years. There are two main forms of bentonite-the western (sodium) and the southern (calcium) forms. Volclay is the most popular sodium form and Panther Creek is the most widely used calcium form. Both types are used as binders for synthetic ( compounded, blended, for­mulated) sand mixtures in making molds, or cores. Sodium bentonite is found principally in Wyoming, South Dakota and Montana in the U.S.A. Calcium bentonite is found chiefly in Alabama and Mississippi in the U.S.A. 



BITUMEN EMULSIONS A general term for pt.troliferous substances ranging from true petroleum through the so-called "mineral tars" to asphalts, which have been emulsified by a caustic or alkali solution and suspended in a sodium bentonite dispersion. These have been used as carbon facings and as core additives in the foundry.

This is called "soft coal" and is the principal coal used when ground-as foundry "seacoal." It is distinguished from anthracite coal by the property of its losing moisture readily on exposure and by its ease in breaking-up into smaller pieces. Bituminous coals vary in quality from "near-lignite" to the "harder grades," nearer anthracite coal. The specific gravity of clean bituminous coal is 1.75 to 1.80. It is found throughout the United States and Canada in North Amer­ica. The best foundry grades appear to be found in Alabama, West Virginia, Virginia, Pennsylvania and some parts of the lower Middle West, including Kentucky and Illinois. Good bituminous coal for use as a seacoal should give at least 13,500 B.T.U's. per pound and should have 30% to 38% of volatile matter. The ash should be less than 6% and the sulphur less than 0.8 % . The ratio of fixed carbon to volatile matter is generally 2 to 1. 


Mixtures called "Blackings" are essentially carbonaceous mate­rials, such as graphite, pitch, charcoal, hard coal, and coke, which may be blended with bentonite, clay, or other ingredients. Blacking may be used in, or coated onto sand molds and/or cores. Blackings are used with, or as a partial clay substitute for wet coating, so as to prevent metal penetration or burn-on. This lowers casting cleaning costs and gives smoother casting surfaces. Blacking protects the mold or core sand surface from attack by the hot metal and its surface oxides. Blackings may contain plumbago, a mixture of various car­bons, such as graphite, hard coals, clays, or carbon forms. Most blackings are formulated to meet the demands of foundries producing specific type castings. Blacking may be formulated so as to contain silica flour or other aggregates. It is best to identify the differences of blacking and plumbago. Blacking is a general designation for the type of facing, mold or core wash which is applied on dry sand molds or cores ( dry sand or oil sand), usually in a syrupy or liquid mixture. Blackings may vary widely. Some contain a binder or an auxiliary binder. Plumbago differs from a blacking mold or carbon core wash in composition. Plumbago's carbon is usually graphite and generally does not contain a binder or auxiliary binder. Foundries use plumbago to give a "soft" surface to the mold or core surface, against which the metal may lie more quietly. Plumbago may be used wet or dry. If used dry, it adheres better to wet sand but the plumbago should be ground more finely in order for it to be worked into the base sands' voids. When it is used wet, a binder must be added. Plumbago may also be added to silica flour washes and coatings. When it is added to any blacking or coating, it should be thoroughly mixed and allowed to stand for a period, then remixed. This permits the water and bond to be homogenized, and it provides an opportunity for the air that was beaten into the coating slurry to escape. The pH value of the wash must gradually become constant before it is used, or settling may result.



Foundry clays suitable for use in sand mixtures to give green, dry, baked and hot compression strengths and which will produce good castings are called "bonding clays." There are many varieties of "bonding clays" from different geographical locations. 

Any substance which binds, or has a uniting influence, is said to be a "bond." Bonds in the foundry may be organic or inorganic. A bond is the connection in which adjacent parts of a structure overlap and develop a mechanical, or in some cases a chemical attraction. This binding together, or connecting together, is said to be a "bond­ing action."

Is an inhibitor used in molding and core sands to cast magnesium and its alloys. The addition of boric acid to sand mixtures varies from 0.25% to 2.0% by weight depending on the alloy cast and its blending with other ingredients of the sand mixture. 

Often termed, "grog." It is brick crushed and reduced to finer mesh size, usually ½" and finer. The fines used for chamotte are less than a 12 mesh grade.

A product used to compensate for the heat shock, or to cushion the brunt of opposing forces. Wood flour and cellulose additions offer such protection in high expansion molding and core sand mixtures. Five Star Wood Flour and Cellflo are highly recommended as additions to sand mixtures and are referred to as buffers. Refer to these products. Clays are sometimes considered to be useful "BUFFERS" in a sand mixture.

BUILDING SAND (See: SAND) An inexpensive sand used as "filling" for the building trade in such materials as cement, plastic, mortar and the like. Building Sand is seldom used in the better foundries for making molds or cores, as it generally contains too much contamination.


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

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