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Green Sand Metalcasting Foundry News

"P" - Glossary of Foundry Additives (including Liquid Parting Products)

Posted by Hill and Griffith Company on Jun 20, 2018 9:39:30 AM

P - Foundry Additives Glossary


It is one of the waxes used for making wax patterns in the "Lost Wax Process." It is used as a release agent for liquid partings when it is dissolved in a liquid carrier such as kerosene. (See: PARAFFIN OIL.)

This is the drip oil from the wax presses in processing an extracted paraffin wax from the wax bearing distillate in the refining of petroleum. The oil is treated, redistilled, and separated into various grades of lubricating oils varying from light to heavy. They may be treated and bleached with sulfuric acid, or neutralized with an alkali. They may be bleached with acid. The specific gravity of paraffin oil varies between 21° and 26° Baume. Paraffin oil is used in many liquid foundry parting compounds when blended with kerosene, which is used as the carrier oil. It is usually soluble in ether, benzene and essential oils.

Materials used to separate patterns from the molding or core sand mixtures. Parting compounds may be dry parting dusted or sprayed as a liquid parting onto the patterns or core boxes so as to prevent any mold or core adherence.




This is a substance used as a fuel in some countries where more efficient fuel such as coal is too expensive. Peat beds or bogs are usually found in moist low lying districts, associated with suitable pro­ducing climates. Peat is an earthy mass formed by the rapid accumu­lation of quick growing mosses and plants. The top layers of peat are only slightly decayed, and are of no specific interest, but at greater depths in the ground, peat is nearly black and very compact and is of better quality. Before peat is used commercially in the foundry, the 80% moisture content it generally contains as mined, must be removed. Foundry peat used to replace cellulose materials, seacoal, or coal dust as carbon facings generally contains about 70% to 75% volatile matter, and 25% to 30% fixed carbon. The calorific value of peat is hardly ever over 5000 BTU. Peat has been used in Europe in molding sands, as a substitute for wood flour and cellulose to help overcome expansion defects. It has not been too widely accepted by the U.S.A. or the North American industry except where large peat bearing areas occur and there is a lack of economical wood flours and cellulose products. (See: CELLULOSE-SEACOAL-WOOD FLOUR.)

Is the dried product obtained from the pancreatic digestion of meat. It is a reddish-yellow to brown powder. It is soluble in water, but insoluble in alcohol. It is a seldom used commercial foundry core, or compound binder, blended with other materials, or chemicals. (See: BINDERS-BONDS.)

It is an oil obtained from the seeds of the perilla plant and is a substitute for linseed oil in certain commercial core oil formulations. It has a specific gravity of 0.94.


It is the final residue in the distillation of petroleum. This petroleum coke is at the bottom of the still and is actually a solid. It con­tains about 99% pure carbon and petroleum pitch in the final distillate before the coke is obtained. It is used in the foundry as a substitute for various other carbons, such as pitch, coal, coke, and other facing­ like materials. (See: ASPHALT-COKE-PITCH-TAR.)

A petroleum polymer core oil plus some linseed vegetable oil gives the same baked tensile strength to a core oil sand mixture as when 100% linseed oil is used. It is a black appearing core oil and generally burns with more smoke or odors when baked than linseed oil. Mineral polymers are by-products of the refining of crude oils. Polymers are widely used in commercial foundry core oils.

Are highly volatile fractions of petroleum which are normally used as solvents in liquid foundry additives. The choice depends on many factors of the manufacturer.

Phenolic resins modified by furfuryl alcohol generally give lower strengths, when compared to modified urea resins. Generally they are used as cold setting organic binders.

Are those resins containing phenol. They also include carbolic acid, ( C6H5OH), which is obtained from the further distillation of coal tar, a by-product of the coke ovens. The terms "Phenols" and "Phenolics" used in the foundry are class names of a wide variety of resinous materials. Phenol modified resins contain some furfuryl alcohol and are accelerated as in the "Hot Box Process." 



Is a substance which forms a paint when mixed with oil or solvent. Pigments give body as well as color to the various coatings or proprietary ingredients used by the foundry. Pigments for foundry use are mostly of mineral origin, such as Klean Surf Iron Oxide, which is used in foundry mold and core mixtures for added color and added properties. Pigments may also be obtained from vegetables or woods, such as from logwood. Animal or fish pigments are obtained from the cochineal and other marine life. Pigments are often classified as "dye stuffs." Black is a color of another animal pigment most often used in the foundry for coloring additives. There are a number of aniline dye stuffs used to color core mixtures and molding sand mixtures. Ultramarine dyes are used in the foundry for coloring, but such shades as black, may actually be adulterated with graphite additions. Most pigments are ground extremely fine for foundry use, so as to give maximum coverage, however granular Klean Surf oxide is available.

Is usually a "gum turpentine" extracted from old pine stumps and branches. The specific gravity is approximately 0.918, and the flash point about 154°F. (68°C.). Pine oil is also extracted with the pine resin, which is used in foundry comm􀀄ercial additives to furnish the correct odor, or scent, or to camouflage another scent. (See: Page 222.)


Because pitch is one of the twenty more widely used sand additives in the foundry, more data is covered. Pitch is one of the many by­products recovered in the manufacture of coke. Pitch is distilled-off at approximately 290° F.-350° F. (1 43°C.-177°C.). It is then graded and ground for foundry use. Baking Type Binder Pitch is called a "Baking Type Binder" as it must undergo a physical change in a sand mixture to produce the dry, baked or fired strengths desired. When heat is applied to the mold containing pitch, the pitch forms a semi-liquid as it melts. The semi-liquid pitch re­hardens on cooling and furnishes a brittle structure to the molding sand mixture.

Coal Tar pitch

Properties Contrary to many beliefs, pitch does not produce green compres­sion strength directly to the sand mixture, however, because of its finer grain size, pitch adds to the molding or core sand's density, therefore a slightly increased green compression strength may be obtained by compaction of the sand mass. In other cases, special pellet sizing of the pitch may not fit into the interstices of the base sand grain distribution, thus the disturbance may cause a lowering of the green compression strength. The function of the pitch is not to furnish green compression strength to the sand mixture, but to produce dry (baked) and hot compression strengths. Pitch bonded sand mixtures develop hot plastic deformation properties. This hot plasticity helps to control undesirable expansion characteristics of certain silica sand mixtures.

Since pitch offers little, if any, green compression strength, it depends on clay and bentonite to furnish the green properties until the baked stage is reached. Pitch can be used effectively with old sand, and makes burned-out sand take on renewed life.

Pitch usually slightly decreases green permeability because it plugs the sand voids, the same as its effect on green compression strength.

Gas Evolution
The gas or vapor cushion produced in the mold cavity when metal comes in cqntact with the minute grains of pitch forms a highly reducing atmosphere. This reducing gas, the same as furnished by seacoal or other carbonaceous materials, allows the metal to lie and flow easier over the sand's surface. Many suppliers state that pitch gas is more uniform in its gas evolution.

Wax Content
When purchasing pitch, the wax content is an important consid­eration. When pitch is used in sand mixtures, the wax content affects the rate of distillation during pouring of the metal.

Combination With Seacoal
Many foundries have found pitch advantageous to use in com­bination with seacoal in molding sand mixtures. Seacoal prevents the pitch from hardening the mold or core too strongly, as the mold or core is cooled after pouring. A 50-50 ratio of seacoal and pitch works very well in most large core and molding sand mixtures, used to cast ferrous castings, other than steel. Additions of dextrin and cellulose to sand mixtures containing pitch give harder surface properties and better collapsibility.

Use For Heavy Casting
Pitch produces good dry and baked strengths and offers moisture resisting qualities to sand mixtures. Dry sand molds which contain pitch, may stand considerable baking, and they collapse at a slower rate after pouring. Most large gray iron and ductile foundries using dry sand, employ 4% to 5% pitch as an indispensable mold binder for casting heavier sections such as machine tools, frames, bases, lathe beds, and other parts. Heavy dry sand molds used in gray iron foundries have found pitch's resistance to moisture absorption of particular value because large cores and molds generally stand for a considerable length of time before they are cast. Pitch bonded sand mixtures must be worked wet when they are used for dry sand molding, or failure to develop dry, baked and hot properties usually occurs. Yet, after baking, these pitch bonded molds and cores resist moisture absorption more readily.

For Lighter Castings
Many lighter gray iron, ductile and malleable foundries add from 0.5 % to 2% by weight pitch to the molding sand depending upon the molding sand's returned condition which contains pitch. It is better to use too little pitch, than too much.

Excessive Additions of Pitch
If too much pitch is used, the baked strength of the molding sand mixture may be very high. The casting shakeout time is increased. When used in correct proportions (on larger castings sometimes as much as 5% pitch is used), pitch offers a collapsible mold or core when the mold or core is surrounded by larger sections of metal, which burns out more of the pitch in the sand mixture. Often medium and large cores are faced with oil sand mixtures and backed with pitch bonded molding sands which contain the correct clay bond. Too much pitch will cause too much smoke in the foundry after casting.

Possible Water-Proofing Faults
Pitch is quite resistant to water, and arguments prevail that when pitch is used in excess, water-proofing of the sand grains in the sand system is noted. Foundry sands which become waterproofed have little water-holding capacity, and as some foundrymen state, "The temper water runs off the sand like water off a duck's back." Molding sands that show this tendency are difficult to work or mold. Unless propor­tioned with new, unused and unbonded sand, reused molding sands may be unfit for molding.

Combinations With Southern Bentonite
When pitch is used with southern bentonite, all dry compression and hot compression strengths of the southern bentonite mixtures at elevated temperatures are increased from room temperature through 2000°F. (1093°C.). In fact, in southern bentonite sand mixtures, pitch increases the dry compression strength about three times. The hot compression strength is increased accordingly. Many malleable foundries use southern bentonite as a bonding agent to obtain the lowest dry and hot compression strengths so as to assure an easy shake-out with less fear of casting hot tears and cracks. Such foundries should check these denied properties when changing from seacoal to pitch, or any asphalt carbon, as pitch has a strong influence on increas­ing these hot and dry properties. The easy shake-out feature of south­ern bentonite may be destroyed if pitch is substituted for seacoal in the molding mixture without other considerations.

Many foundries do not realize they are using pitch or gilsonite when purchasing certain commercial cellulose or core compounds. It is common commercial practice to blend pitch or gilsonite with cereal, dextrin, goulac, clay and other additives in proprietary compounds to give certain properties. It is wise to know the type of such additives in these commercially purchased compounds, so as to formulate cor­rect foundry mixtures for specific usage. Too much high dry com­pression strength ingredients may be wrong for what is desired by that foundry.

Pouring Cups or Basins
Many foundries, including steel, have found it advantageous to make pouring cups bonded with pitch or pitch compounds, in order to use waste sand in the foundry. A satisfactory formula is:

1000 lbs. - system sand bonded with at least 5 % Vol clay bentonite 50 lbs.-pitch
• Add a molasses, glutrin or dextrin water (10: 1 ratio) to the above formula to give proper temper.
• Mull the mixture until the correct consistency is obtained, then discharge it and mold the pouring cups. Bake the cups in an oven at 600°F. (316°C.) until cured.

Effect of Pitch on General Sand Properties
Green compression strength of the sand mixture is generally slightly increased due to the finer pitch increasing the rammed mass density of the molding mixture. Pitch has little adhesive green strength when compared to clay or bentonite. The baked strength of the sand mixtures up to 600°F. (316°C.) is greatly increased when pitch is added. The hot compression strength, that is above 600°F. (316°C.) decreases when pitch is present. Collapsibility is noted, as pitch in its own atmosphere prevents hot compression strength from developing above 600°F. (316°C.). Permeability is decreased due to the finer pitch filling the sand grain voids. Flowability of the sand mixture doesn't seem to be impaired by the use of pitch unless the higher temper water in the sand mixture increases the deformation too greatly. Green deformation is increased slightly, but as temper water increases, so does the deformation. At higher temperatures, the hot plastic deformation values increase readily. Pitch bonded sand mixtures have high plastic deformation values due to the sticky, liquefaction of the pitch when it undergoes the casting temperatures. As the pitch melts, the sand grains are glued together. Toughness of the sand mixture is increased as the temper water increases. Mold hardness is increased, but only when the temper water is controlled at lower levels to permit ramming quality and workability of the mixture.

"Plasdon" and "Plaston" are commercial names. There is also a "Plaskon" which is a commercial name for a plastic resin made by the Allied Chemical Company. "Plaskon" is an urea formaldehyde. (See: UREA FORMALDEHYDE RESIN.)

Is also called a "molding plaster". It is used for making molds in investment casting. It is also used for making certain temporary patterns. An insulating sleeve of a special type is made for the non­ferrous foundries with molding plaster. Plaster of Paris is made by heating gypsum above 230°F. (110°C.) which forms the semi-hydrate (2CaSO 4 • H20). When this dry powder is mixed with water it forms a hydrated sulphate that solidifies due to its interlocking crystallization. A higher percentage of water is required, but lime water, glue water or mucilage mixed with water are frequently used as the lubricant.  

A bonding clay used in molding and core sand mixtures.

There are approximately 39 families of finished, fabricated plas­tics used in the foundry today, each having certain special advantages and characteristics. There are hundreds of raw resins available and numerous commercial grades. An abbreviated list of some of the fabricated plastics is as follows:

ABS ... (for acrylonitrile-butadiene-styrene) ... strong and tough, having outstanding impact strength plus high tensile strength.

Acrylic ... exceptional clarity and light transmission in clear form, excellent when used as an insulating material, and is unaffected by weather.

Amino plastics ... (melamine and urea) ... very hard, scratch and shock resistant, as well as being unaffected by detergents.

Epoxy resins ... used widely for surface coatings and adhesives because of their excellent adhesion, durability and resistance to chem­icals and weathering.

Ethylene-vinyl acetate ... flexible over a wide range of tempera­tures, with excellent "snapback" flexibility and high impact strength.

Fluorocarbons ... exceed the temperature range of all other plas­tics, and possess unmatched anti-sticking and chemical resistance qualities.

Phenolics ... hard, rigid and strong, resistant to high temperatures and give a smooth lustrous surface. Very prominently used to bind cores and mold castings.

Polycarbonates ... high impact strength, heat resistance and rigid­ity, with an ability to withstand blows.

Polyesters ... strong, tough, highly resistant to most solvents, acids, and salts, with a low water absorption rate and good weathering qualities.

Polyethylene ... the most widely used plastic today. It can be made flexible or rigid; moisture-proof, highly resistant to breakage and to extremes of temperature.

Polypropylene ... the fastest growing plastic in use today; has a superior surface abrasion resistance, but also possesses long life under flexing conditions.

Polystyrene or styrene ... has many valuable properties in regard to texture, coloring, resistance and strength. Used as expandable cores.

Polyurethane or urethane ... tough but flexible foams in a broad range of firmness and resilience and in varying densities, for cushion­ing, shock-or-sound absorption and heat insulation. Used as coatings of metal and core boxes.

Vinyls . . . Strong, tough, abrasion resistant. A wide spectrum of properties can be built into the various vinyls. Most types unaf­fected by water, oil, foods, common chemicals, gasoline, or naphtha.

Polyvinyl chloride . . . ( often called PVC). Unlimited colors, toughness and high resistance to chemicals. Polyvinyl acetate ... used in paints, coatings, washes, and ad­hesives.

Contains many formulations but usually it is in a ground form containing mixtures and blends of graphite, black lead, silver lead, soapstone, talc, bentonite, or clay. It is used in "blacking coatings" and many foundries have used it for foundry sand additives. Plum­bago was first rubbed or brushed onto the mold as a facing. Plumbago differs from a mold or carbon core wash in composition. It was at first not intended to be a wash, so its composition varied. Its carbon is usually graphite and plumbago most generally does not contain a binder or auxiliary binders when it is rubbed, dusted or brushed onto a mold or core surface. Foundries use plumbago to give a "soft" mold or core surface, against which the metal may lie quietly. It is now used wet or dry, but the application should be specified when the plumbago is purchased. If it is used dry, it adheres better if the sand is first wetted. Plumbago should be finely ground in order for it to work into the mold or core sand grain voids. If it is used wet, a binder must be added to it. Plumbago may also be added to silica flour coating mix­tures. A "blacking" is usually a plumbago with binders and water added. When plumbago is added to any blacking wash or coating, it should be thoroughly mixed and allowed to stand, then remixed before use. This permits the water and bond to "blend," "age," and "equal­ize. " Standing, before use, also allows the air a chance to escape. The air is beaten into the blacking slurry as it is mixed by agitation.

A buffer used in steel sand mixtures. It is an organic polymer composed of multiple units of acrylamide. It is made by dissolving acrylamide in water. It is polymerized into a thick, viscous solution. The final product is a clear, colorless solution having very high viscosity. As a film and dry strength former, 0.25% polyacrylamide substitutes for over 1 % by weight cereal in foundry sand mixtures.

Polymers (organic polymer) are highly deformable, organic, compounds composed of repeating chains of organic constituents. Polymers may be natural, as in latex rubber, or synthetic as in trans­parent lucite or cellophane sheets. Organic polymers are normally used for their film forming tendencies and differ so widely in their structure, properties, chemical composition and behavior in foundry core oils that it is impossible to cover all of them completely. 

The petroleum polymers or polymerized oils sold as "core oils" are usually petroleum polymers combined with drying oils. A petro­leum polymer oil, plus some linseed vegetable oil actually gives the same tensile strength as 100% linseed oil in almost all cases. Polymer core oils still require a high percentage of oxygen during baking of the core so as to cure the binder properly. Core oils are usually not total polymer binders, but blends of polymers for foundry core use.


It is a cement produced by grinding a heat-treated mixture of calcereous and argillaceous materials. These materials are: sandy limestone, chalk, marl, shale, weak siliceous clay, slag and a few special chemical ingredients. Rotary furnaces (kilns) are generally used for the heat treating or calcining. Calcined cement contains 25% to 60% of tricalcium silicate, 7% to 45% dicalcium silicate and about 10% of tricalcium aluminate. (Refer to ALUMINATE CEMENT)  

Is a commercial chemical compound used in the foundry as an inhibitor to prevent burning of the metal in casting magnesium in molding sand mixtures.

Its chemical composition is (KBF4). Its molecular weight is 125.9. It is prepared from reactions of boric acid, hydrofluoric acid and caustic potash. It is slightly soluble in water at room temperature, but very soluble in boiling water. It is used as a fluxing agent in the foundry industry and as an inhibitor in casting magnesium in foundry sand mixtures.


A material dusted on the pattern or core box to prevent the sticking or adherence of the core or molding sand.

A premixture is two or more additives blended together before adding it to a final product. For example, bentonite, clay, seacoal, and cellulose held together with 10% to 15% water is one such pre­mixture used in green sand foundry mixtures. It is a one unit foundry sand additive.

The foundry generally refers to them as "protein plastics." The oldest of the protein plastics is casein plastic which is used in foundry core pastes and core compounds. Organic plastics of this nature are precipitated proteins from animal and vegetable products.

Binders, principally clay binders, are finely ground bonds. Most bonds are reduced in size so as to give maximum surface area when they are added to sand and then tempered with water. When this sand mixture is mulled, strengths are developed so that the mixture is moldable.

As used in the foundry, pyrophyllite is an aluminum silicate mineral. It has properties similar to clay, but it also resembles talc. Its chemical composition is [H2Al2(SiO3)4]. Many foundrymen con­sider it identical to talc in structure and appearance, but others feel that it has kaolin properties and is used in many refractory materials because it has practically no volume change and does not crack or spall when fired and then cooled. It has a Moh's hardness of 1 to 2. Its specific gravity is approximately 2.8.

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

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