<img alt="" src="https://secure.hims1nice.com/150891.png" style="display:none;">

Green Sand Metalcasting Foundry News

"D" - Glossary of Foundry Additives (including Dry Parting)

Posted by Hill and Griffith Company on Jan 10, 2018 12:14:57 PM

D - Foundry Additives Glossary

Foundry dextrin is usually a bright yellow or white color. It is completely water soluble and forms a syrup. It is a concentrated starch product. Dextrin is produced by the acid digestion of pure corn starch. When used in molding sands it adds little green compression strength to the sand mixture, but as the temper water migrates to the mold's or core's surface when left standing, dextrin adds exceptionally high dry surface strength. Usually the amount of temper water in the sand mixture determines the dry compression, or shear strength. It is com­mon in the foundry to use dextrin where inner dry compression strength is required, and where dry compression strength is necessary to hold and provide detailed edges of the mold or core. Dextrin weighs approximately 1.3 to 1.4 lbs. per quart, or 39 to 42 lbs. per cubic foot when purchased as a foundry additive. Cereal and dextrin are widely used in the foundry industry as binders. The steel foundry has practiced the use of dextrin perhaps more widely than other foundries. It gives very high skin hardness to molds or cores which contain it. The higher the moisture content of molds bearing dextrin, the harder the surface of the molds and cores, particularly if they are later baked in an oven. Dextrin is a powerful binder and is made by moistening starch or cereal with a mixture of dilute nitric and hydrochloric acids, then exposing this mixture to a temperature of 212°F. to 259°F. (100°C. to 125°C.) for a given period. Dextrin varies in grades due to differ­ences in the starch from which it is made. Dextrin has been called "British Gum" and "Amylin." There is a group of compounds which have the same formula as starch [C6H10O5J.

Although diatomaceous earth is not widely used in the foundry, it is a hydrated silicate of the same composition as the opal. At times it has been referred to as a clay, but it is mostly like Tripoli and Kieselguhr. It is sometimes called "Diatomite" and 90% of its vol­ume is porous. It has great absorptive powers and most often holds five times its volume of water. The apparent density of diatomaceous earth in the commercial form occasionally used in the foundry is approximately 12 lbs. to 17 lbs. per cubic foot. It is very light and has been used for insulating purposes in the foundry. It is used in some insulating cements, mortars and mold coatings. It can withstand tem­peratures up to 1900°F. ( 1038°C.). Diatomaceous earth has func­tioned as a replacement for asbestos fiber for insulating purposes in the foundry but has limited use as an additive in molds or cores at present.




Any sand which has been dried mechanically to remove its water before commercially used in the foundry.

Ammonium nitrate, cobalt salts, iron salts, potassium permanga­nate and a few others are added to core oils to hasten baking time.


A few dryers used in certain core mixtures are: ammonium ni­trate, cobalt salts, iron salts, and potassium permanganate. These hasten baking time of core oil binders.

1) Vegetable oils such as linseed, tung*, chinawood and soybean are drying oils. 2) Polymers, either mineral or vegetable, are the faster drying oils in core mixtures. 3) Marine, fish, and animal offer the lesser baked tensile strengths. * Tung and china wood oil are synonymous.


Dyes or "dye stuffs" are substances which give color to various molding sand and core sand mixtures in the foundry. The dyes may be mineral, animal, or vegetable dyes. The artificial dyes are mainly derived from coal-tar residues, whereas vegetable dyes are water­soluble and are made from woods, flowers, leaves, barks and such. Mineral dyes are extracted from such natural minerals as hematite, ochre, limonite, and others. Marine dyes are obtained from various snails, conchs, and many forms of marine life. Small amounts of dyes color sand mixtures to any degree desired.

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


Early registration for 122 Metalcasting Congress ends soon

The deadline for Metalcasting Congress early registration is Feb. 1.

Don't miss out on a discounted price for next April’s event at the Fort Worth Convention Center in Fort Worth, Texas!

Click here to register for the 122nd Metalcasting Congress. This is the leading event for education and networking. For more information on Metalcasting Congress, please click here.

Housing is now open. The deadline to book your hotel is March 12. For more information on lodging and transportation, please click here.

Questions? Contact Registration at 224-563-3770 or metalcasting@compusystems.com

Metal Foundry News - From Google 

Reclaimed Sand Market : Global Forecast over 2025

Custom Casting Services Market Overview and Scope 2018 to 2025

At the pouring of SAG's 'The Actor' statuettes, Ann Dowd and Clea DuVall geek out over the process

Hill and Griffith Customer Service

The Hill and Griffith Company's green sand metalcasting foundry supplies help achieve the EPA's M.A.C.T. standards and reduce Benzene emissions. Our variety of environmentally sound release agents, coatings, partings, lubricants, core oils and specialty products will help you meet your metal casting's needs. We're known for our hands on approach. Let us visit your plant and recommend products that suit your needs.

Hill and Griffith Samples

Product Samples

We are pleased to provide samples in quantities large enough to allow you to "try before you buy."
Contact Us »


Hill and Griffith Customer Service

Technical Services & Support

On-site casting defect investigations, product testing, machine start-ups and much more. Also, lab facilities are available to provide testing upon request.
Contact Us »

Bulletins and Technical Papers for Metal Casting Products


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, Foundry Additives Glossary

Subscribe to the Green Sand Metal Casting News

Recent Metalcasting News

Follow Me

Metalcasting News Categories

see all