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Green Sand Metalcasting Foundry News

"N" - Glossary of Foundry Additives (including Core Binders)

Posted by Hill and Griffith Company on May 15, 2018 3:26:40 PM

N - Foundry Additives Glossary

Is also known as "NAPHTHALIN"-"WHITE TAR" or "TAR CAMPHOR." Its chemical composition is [C10H8J. Its molecular weight is 128.2. It has the odor of mothballs and is derived from coal tar where it is the most abundant single constituent. It is crystallized from the middle or "carbolic oil" fraction of the distilled tar. It is con­tained in a few liquid sprays used in the foundry, such as certain liquid partings.

A hard resin left after distilling-off the volatile oil of turpentine. It generally has a higher melting point than other resins. The natural resins are used as supporting sand core binders in making heavy cores or molds which require baking. Resins work best with higher temper water levels in a foundry sand mixture. They also work best where clay is used in the sand mixture. Rosin is blended into core oil and enhances core mixtures which contain cereal, dextrin, lignin sulphite and other water soluble additives.


A sand which contains sufficient clay bonding material as mined, to satisfy foundry molding properties is said to be a naturally bonded sand. Molds may be made from this naturally bonded sand by pre­paring, mulling, and tempering it for use. Additives may be made to this molding sand, so as to give properties required to produce cast­ings in the foundry. Such sand may be used as an additive to synthetic (BLENDED or FORMULATED) sand mixtures which are called, "Semi-synthetic sand mixtures."

A commercial waterless binder that gives mirror-like surface quality to lightweight castings. Neo-Bond is a special waterless binder. Only 5% by weight is added to new unbonded sand with 1.25% to 1.40% of a high viscosity oil added for tempering. When the Neo­Bond, sand and oil are thoroughly mulled, this waterless binder mix­ture may be used to cast aluminum, magnesium and lightweight copper-base alloys. No water is required in the mixture, and changes in formulae may be made, depending upon the section thickness and weight of the castings produced. No alcohol is required with Neo­Bond mixtures. There is less smoke and less danger of flash fires because of the absence of alcohol during the casting and shakeout period. Castings close to pattern size can be produced. Core boxes and patterns are produced from these mixtures.

A refractory material which is neither acid nor basic. However, the term is merely relative in most cases, since at high temperatures such a material reacts chemically with a strong base, functioning as a weak acid; or with a strong acid, functioning as a weak base. Chrome refractories are the most nearly neutral of all the commonly used refractory materials. All R2O3 minerals are considered neutral refractories, such as Al2O3, Cr2O3, Fe2O3, and a few others.

A no-bake process. (See: SODIUM SILICATE)

A no-bake binder is one which, when mixed with sand and an appropriate catalyst or accelerator, produces a castable sand mass which hardens without the external application of heat. This definition is more narrow than that of the term, "self-curing" in that it ex­cludes binders of the oxygen-curing oil type, or any that, from a practical stand-point, require baking in an oven prior to casting. Sodium silicate and cement are also no-bake binders. Some sodium silicate mixtures and cement bonded sand mixtures may be fluidized for making molds and cores. Ground ferrosilicon may be used as a hardening agent. Dical­cium silicate, including metallurgical slags, synthetic dicalcium silicate, and Portland cement are also used as binders. Finely ground 70% dicalcium silicate is also used. Portland cement manufactured from blast furnace slag is a binder. Organic materials known as "ascetins" or "latent acids" are used as hardening agents for dicalcium silicate sand mixtures. Ascetin hardeners are glycerol mono-, di-, or tri­acetates. Only 12 % of the binder is the amount of catalyst. Two fluidized silicate processes have been developed. In Russia, sodium silicate and cement plus a wetting agent is used. The cement provides a dicalcium silicate content. Foaming action occurs and the fluidized mixture is then cast and molded. The Japanese process uses a wetting agent to render the sand mixture more castable. The wetting agent is a nonionic type. Eight (8) percent of cement, plus eight (8) percent or more water is used. Only 0.3 to 0.5 fluidize agent is re­quired for the sand mixture. No-bake binders may also be thought of as high furfuryl alcohol-phenol-modified resins or urea furan type binders used in foundry sand mixtures. Urea-formaldehyde furfuryl alcohol is a no-bake foundry binder. No-bake oils, or binders, are chemically related to poly-urethane driers such as cobalt naphthenate and one of the methyl-phenyl-di­isocyanates (MDI). Binders can be purchased commercially as a two or three packaged system. A two package system has the drier mixed with the oil. A three package system is achieved by varying the drier type and percentage. An accelerated cement sand mixture with an isocyanate alkyd resin added may also be considered a no-bake type binder.

Is a polymer of furfuryl alcohol and formaldehyde which is hardened by an acid catalyst. Phosphoric acid is usually the catalyst. Sand chemistry is most important, as the weak acid is easily neutralized by alkalies in the mixture. This system is more widely accepted for the casting of heavy or large work. (Also see: SELF-CURING BIND­ERS-AIR-SET BINDERS.)

NOCOL is a blended carbon additive. It is a controlled carbon which is combined with bentonite, either Volclay and/or Panther Creek. It contains materials which have specific water-holding capac­ities. NOCOL eliminates the necessity of several small increments of additives by one single measurement.
92% sand, 5% bentonite, and 3% NOCOL can be mulled into a sand mixture with about 2.5 % temper water. This sand mixture may replace those containing many additives such as cellulose, auxiliary binders, clay, bentonite, pitch, seacoal, cereal, etc. This simplifies the work and the mixture control at the muller.
NOCOL prevents sand grain surfaces from eroding on the mold surface when the mold is left standing, heated, or poured. bing, buckling, NOCOL furnishes a reducing atmosphere, thus inhibiting scab metal penetration, and other expansion defects. With the introduction of automated high pressure molding, NOCOL is the recommended single additive. NOCOL aids the sand mixture to move laterally against the pattern if the mold is made by squeezing.


Liquid phenolic formald􀀝hyde resins that are used in a warm (hot) coating of sand at about 275°F. to 325°F. temperature. It is produced with 4%-8% alcohol present. Novalak is used to prepare the coated sand mixture for use in shell coring or molding. Novalak resins may also be purchased as flakes, granular or droplet forms.

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

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Tags: Metal Casting, Green Sand Casting Products, Green Sand Foundry Supply, Foundry Supply, Metal Casting Supplies, Foundry Supplies, Green Sand Metal Casting, Green Sand System, Green Sand Metalcasting, Core Binders, Foundry Additives Glossary, Green Sand Additive Products, Green Sand Foundry Supplies

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