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Green Sand Metalcasting Foundry News

"G" - Glossary of Foundry Additives (including Blacking Products)

Posted by Hill and Griffith Company on Feb 20, 2018 6:01:06 PM

G - Foundry Additives Glossary

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.

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.

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.


Chemical Analysis of Gilsonite.jpg

Gilsonite as a Mold Coating 

In making certain mold coatings or sprays, gilsonite is suspended in a solvent such as gasoline, alcohol, or toluene solutions which are applied to the mold. The mold is then lighted-off and a carbon film remains on the sand grains, thus acting as a coating. Gilsonite is soluble in alcohol, carbon tetrachloride, turpentine, kerosene, and mineral spirits, but gilsonite is completely insoluble in water.

Economy of Use
Gilsonite has the advantage over other carbonaceous material in that lower additions are required. Substantial monetary savings are claimed in avoiding the handling of larger amounts of other carbon materials required. Freight costs and storage costs are decreased when gilsonite is used. Minute quantities of gilsonite are encouraged with each new sand addition, as little gilsonite is lost in the sand system from use. This avoids "building-up" of carbon in the unit system.

Smoke or Flare-Up
Excessive amounts of gilsonite or pitch in the molding sand both produce great quantities of smoke and "flare-up" when the metal is cast, or when the copes are removed quickly from the drag. This con­dition is quite noticeable when casting larger, heavier, dry sand molded castings. 3% to 4% gilsonite is usually added to dry sand mixtures. If cranes sharply remove the larger copes, much smoke and flare-up from molding sand containing pitch or asphalt-like carbons is noted in a closed foundry.

Avoid Excessive Additions
As stated in previous chapters, too much of any additive, includ­ing gilsonite, may result in higher casting scrap losses. This is the same as in adding any foundry material in excess over the recommended amount. Sand losses may be quite great if an increased lumping condition of the molding sand develops from excessive gilsonite additions. Reclamation costs may also be extremely high, if excessive additions are allowed. Foundry equipment suffers from extreme cases, and repairs will be continuous, if too high a hot compressive strength is created by excessive additions of any binder which adds to excessive baked strengths. Many smaller foundries make the mistake of adding too much gilsonite in facing sand mixtures, forgetting that the backing sand contains almost as much gilsonite as was first introduced. If used too freely in the facing sand, gilsonite builds-up in the heap sand and the foundry returns to trouble due to excessive hot compressive strengths.

Avoid Waterproofing
Both gilsonite and pitch may waterproof sand grains. Volatile matter must be tested and controlled. Seacoal, if used in excess, has the same tendency to waterproof sand grains. Tar matter in the sea­coal exudes from the tiny seacoal grains when it is coked under heat of the metal, and pitch-like action on the sand grains occur.

(1) The properties of gilsonite (the mineral) resemble the prop­erties of pitch (the coke by-product).
(2) Benefits derived from using gilsonite are just as effective as any foundry product. Control must be established as with any product and closely watched.
(3) Less additions of gilsonite to molding sands are required than with seacoal additions.
(4) Combinations of gilsonite, seacoal and/ or wood flour work excellently as blends in foundry sand mixtures.

Is a high purity silica sand used in the making of glass. Glass sand has very low impurities.

Is the binder of a cementing quality made from impure gelatin obtained from the clipping of animals and hides. It is also made from the skins and heads of marine life, and it is extracted from various bones. Glue is a widely used name having many grades and qualities. Bone glue, sinew glue, albumen glues (made from blood or from casein), animal glues, marine glues, dextrin, mucilage, and ethers are used for bonding cores, molds and other products in the foundry. Various forms of casein are used in core pastes and in refractory products. Hide glue appears to be the strongest of the group and in certain cases, white lead is used to make a glue partly moisture-proof as in the case of one commercial foundry core paste. Isinglass is also used as an ingredient to make glue stronger where it is used as a foundry core compound. Glue is also used in the pattern shop of the foundry, so as to join various parts.

Is a commercial liquid lignin sulfite used as a binder in core or molding sand mixtures, particularly those containing some clay. Glutrin reduces core oil consumption, if fines are present in a sand mixture. When added to core or mold mixtures, glutrin produces sharper edges on molds and cores, having higher hardness and better green compression strength. It is not recommended for use where no clay is present in sand mixtures. Glutrin is sometimes added to the temper water for molding sand mixtures, so as to give added dry strength and better skin-drying characteristics. Glutrin works well with pitch and gilsonite bonded core and mold mixtures. It is an excellent wetting agent for use in sand mixtures.

Glycerin is also called "glycerol." It is a tri-hydroxy alcohol having the chemical composition [C3H5(OH)3]. It is soluble in water and in alcohol. It is a by-product in the manufacture of soap. Glycerin is used widely in the foundry industry. It is used as an anti-freeze liquid, as well as an additive to synthetic (compounded) molding resins. Glycerin when used with litharge (lead monoxide) makes an excellent cement for various applications in the foundry. The double­ distilled glycerin used in the foundry has a specific gravity of 1.3 and is added in certain sand mixtures, so as to prevent the low water in synthetic sand from drying out.  



A dry form of lignin recovered from paper-pulp sulfite liquor. It is a commercial foundry term, which refers to a solid lignin sulphite binder. In the preparation of pulp from wood chips, the lignin portion is separated from the cellulose by chemicals which dissolve the lignin. The lignin solution is a by-product of the paper pulping industry. Goulac is an auxiliary binder used in sprays, mold or core washes, core binders, green sand mixtures and many other facets of foundries. It is completely water soluble and acts the same as sugar in water. It is similar to dextrin when used in foundry sand mixtures, in that as water is driven from the core or mold, the dry compression strength is then developed. Goulac or glutrin work well where clay bonds are added to the mixture, as they do not diminish the strength of clay-like 
minerals such as other auxiliary binders may do. Goulac works well in combination with core oils, core compounds, cereals, and particu­larly when clay is present in any of the numerous foundry compounds.


Are cellulose materials such as oat or wheat grains and hulls which are mechanically reduced to fines and used as cushioning agents, or "buffing agents" in core and molding sand mixtures to overcome sand expansion difficulties. Grain cellulose increases flowability and promotes a reducing atmosphere. Cellflo is the most popular grain cellulose used by the foundry.

Graphite is sometimes called "Plumbago" as well as "Black Lead." It is in two forms, foliated and amorphous. Amorphous graphite is used more widely for foundry facings, foundry carbons and blacking products. Graphite varies in various areas from which it is mined, for example, Ceylon produces a very high grade; other grades of different purity are mined in Mexico and the U.S.A. Those mined in the U.S.A. are called, "domestic." The imported amorphous graphite comes largely from Mexico, the crystalline is from Ceylon, and the flake type from Madagascar. Some varieties contain as little as 35% of graphite carbon, but the No. 1 flake graphite contains as much as 90% graphitic carbon. Graphite is not affected by higher temperatures. Ground graphite ore is generally used for foundry facings. Graphite is also made artificially in electric furnaces. Such graphite has high purity, even though it is artificially produced. Metal does not wet sand mixtures containing 1 % or 2 % of graphite and most of - the better blackings, plumbago, and carbon mold and core washes have graphite as part of their total composition. Graphite is also dusted on molds to improve casting finish and is used with coal in many sand mixtures to add refractoriness and promote better casting finish. It is used in foundry facings, lubricants and crucibles.

Is a water tempered sand mixture, whether naturally bonded or a compounded sand mixture, which has been mulled, mixed or pugged and then used in the dampened state to make molds or cores. It is the most widely used molding method in the casting of metals. It is the most economical and is more easily controlled.

There is a continual effort to develop better casting finish and closer tolerances for specific castings produced in the foundry. As foundries obtain better casting finish, newer carbon materials are con­stantly introduced. Green sand foundrymen agree that if they presently apply what they already know, green sand molding would be far ahead of what many processes claim. Sand molds can, and are, producing castings as close to pattern size, as other processes claim. The larger the casting, the more reason for using sand molding. The more difficult the shape of the casting, the more sand molds are preferred. Every foundryman knows, all too well, how quickly the public accepts a new process simply because it is "new." From time to time a new process will claim better finish, closer tolerances, lower costs, better molding conditions, and other sales points. It is not the process that makes for better castings with improved casting finish, but the control, supervision, method, equipment, and the base materials which are incorporated in the process that dictates the final casting results. Even today, castings formerly made in shell cores have returned to green sand via stack molding and equal casting results have been obtained, but at greatly reduced costs. Green sand cores made hollow by high pressure squeezing have also opened larger markets in the industry.

Definition of Green Shell Carb
Out of the laboratory and into the foundry has come a product that seems to be the simplest answer to casting problems. Green Shell Carb is a cellulose carbon which is a special blend of a volatile carbon, a graphitic carbon and a fixed carbon. The amount of hydrocarbon added to the cellulose is very important. This cellulose carbon is growing rapidly in use. A molding mixture which has produced castings of exact dupli­cation is as follows: 

Gilsonite 2.jpg

Addition of Naturally Bonded Sand
Some foundries desiring extremely fine casting finish have found that fine naturally bonded sand containing no more than 12 % AFS Clay Content can be added to the above formula giving further im­proved casting finish. The temper water is easily controlled by this semi-synthetic (blended) mixture. It requires from 5% to more than 15% of these finely divided naturally bonded sands to give good molding characteristics to the above mixture. Some foundries that stack mold use this blend very well.

Mulling of the sand mixture is important. With all new materials, it is recommended that not less than a five (5) minute mulling cycle be used with vertical wheel mullers. Not less than a ninety (90) second cycle should be used with the more rapid rotating, or hori­zontal wheel mullers.

Selecting The Base Sand
There are different techniques which vary from foundry to foun­dry, but all agree that it is necessary to select a fine, carefully controlled and graded base sand. The Green Shell Carb can only perform its function providing the base sand is carefully selected and is of the grain fineness number specified. 

Many things make for better casting finish and surface, but the base sand grain is the most important factor. The finer the base sand selected, the better the casting surface. Finer base sand is the "key" to better and closer casting tolerances. A coarse base sand does not give a good casting finish. A coarse base sand requires many fines to fill its voids, so as to prevent the hot metal from penetrating the mold or core.

Additives required to fill coarse base sands are more expensive than using a finer base sand. Finer base sand should be considered before contemplating the addition of other ingredients to improve casting finish. Molding base sands with a distribution over four, five, or six adjacent sieves are claimed to be much better than the customary two or three-screened sand. 

If a process states that it, and it alone, is responsible for better casting finish, it is then time to study the raw materials which are re­quired in the recommended mixture. Note particularly the fineness of the base sand which is recommended for that process. Compare the fineness of the sand recommended with the sand presently being used in the foundry. 

Casting Design
If the casting design is not too complicated, the casting shou1d be made in a green sand mixture. If there are considerable amounts of deep and narrow draws, such as fins, or other complicated designs, then the pattern should be considered for other sand molding processes where it may belong. However, most castings can be produced in green sand molds with Green Shell Carb as a molding addition to satisfy management, as well as the customer's reaction to the casting's quality. When making a comparison between a present process and a "new" process, always compare "like to like and equal to equal." The economics of the new vs. the old can only be evaluated on this equal basis. Possibly, by improving or investing in the old process, a less total cost can be achieved.

Casting Sales Appeal
Each day there is a stronger effort for what has become known as "casting sales appeal" to the buyer. Green Shell Carb actually produces castings more favorable to the casting buyer. If the pattern possesses the accuracy desired, a Green Shell Carb sand facing mixture, covering one inch or more of the pattern, gives the desired properties to produce pattern-like castings. Better sand practice is growing, and in a few years, the machine shop will suffer, as castings are becoming closer to pattern size with less machining required. To properly satisfy casting customers today, the foundrymen must give more attention to improved casting finish. Companies pro­ducing die castings, permanent mold castings, investment castings, fab­rications and others sell chiefly on surface appearance. Closer tolerances, casting surface finish and dimensional accu­racy are directly related to molding sand properties and the casting methods employed. Foundry progress can be advanced considerably by first making the most of what we already know! By utilizing a finer base sand in the mixture and Green Shell Carb as an additive to give improved casting finish, progress shall be advanced.

A finely ground ceramic product, usually refractory, used in the foundry for furnace and ladle linings, as well as for use as a sand in core and mold mixtures.

Gum is usually a name applied to the extruded sap from a tree. Such tree gums as "satin walnut," "red gum," and "sweet gum" are used as additives for various commercial binders, core pastes, and core compounds. "Pine gum" and various "timber gums" are also used in foundry binders and pastes. "Cotton gum" and "black gum" are found in various states and are added to certain commercial binders, pastes, and foundry coatings. Another form of gum-like characteristics is a gelatinous substance from various species of sea­weed and algae. This is called "Agar-Agar." When dissolved in water "Agar-Agar" forms a jelly and now replaces gums and synthetic resins in many commercial foundry compounds, binders, and refractory coatings offered for sale. Many mold washes and mold coatings con­tain gums such as "Agar-Agar" or "Kanten," which are from a variety of gelatin substances that give excellent adhesion to mold and core coating products.

It is not always necessary and sometimes expensive to incorporate gums in certain desired molding or foundry compounds, but it is discussed because gums are foundry ingredients or binders. One of the most satisfactory is "gum tragacanth." This material comes in flakes and when soaked with water it expands, and half dissolves into a sort of jelly. To prepare this jelly for use, a ratio of 6 grams of dry gum tragacanth flakes is added into 500 cc of water. The gum is soaked in the water for at least 24 hours. It is thoroughly stirred and strained through a fine screen, or a piece of cheesecloth. A few drops of carbolic acid or formaldehyde may be added to prevent fermentation.

Gum arabic may be used instead of gum tragacanth as an ingre­dient for various foundry compounds. Additions of prepared gum jelly allow mold or core washes to spread more evenly, if they are applied by brush or swab. Mold washes using from 2 % - 5 % western bentonite as a suspending agent may profit by using a small amount of the gum jelly preparation in the final mold wash or coating.

Dextrin is also used with some gums to furnish similar properties. The dry surface strength of a coating is increased tremendously, and rubbing-off of the applied wash on the mold or core is avoided when they contain some gums.

It is also called, "Acacia Gum" and is extruded from a small tree found in the East Indies, Africa or Asia. It is used for various ad­hesive purposes in ceramics and in various compounds such as core pastes and other binders used in the foundry industry. It is soluble in water, but insoluble in alcohol.

Gums are carbohydrates of complex structures which are formed as decomposition products in many plants. They are particularly common plants growing in very dry regions. They have neither taste, color, nor odor and are insoluble in alcohol and ether. Many gums are sol­uble in water, while others unite readily with water to form a mucilag­inous product or swell greatly in water. Gums are employed in making adhesives and the gums may be grouped according to their plant origin or source as follows: plant and tree exudates such as gum arabic and gum ghatti are popular gums used in many foundry compound mix­tures. These are usually used for core pastes in the core room. While a great many plants form gums, only a few of these are of any impor­tance to the foundry industry. Perhaps gum arabic, a product from the acaci (acacia) tree of tropical Africa is the best known of all the gums. Ghatti gum is an exudation from the stem of the "Anogeissus Latifolia Wall." It is obtained in India and Ceylon. It forms yellowish tears that are almost completely soluble in water and in this respect it resembles acaci gum. The soluble portion contains the calcium salts of ghatti acid which consists of about 50% pentosans and 12% galac­tose or galacturonic acid. These gums are used frequently by com­mercial foundry compounders in preparing various materials for foundry use.


Gypsum, a hydrated calcium sulfate, with a chemical composition [ CaSO 4 • 2H20 J, is the mineral from which "Plaster of Paris" is made. Plaster has wide usage in foundries for pattern making and for use in investment molding. It is rarely used in molding sand. It has a Mob's hardness of 1.5 to 2.0 and its specific gravity is 2.228 to 2.33.

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