Clay & Minerals

Price: $1.25
1.00 LBS
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50# bag
200 mesh Western Bentonite Available by the pound or in full bag quantities for best pricing. The full bag from the mine is a 50# bag; brown bag, blue text Volclay, Bentonite
Western Bentonite (sodium bentonite) is most frequently used by potters and is the only type Bracker's carries. Southern Bentonite (calcium bentonite) is not available at Bracker's, but can be found at some metal casting foundry suppliers.
Bentonite is a very fine-grained (colloidal) clay of the montmorillonite type containing bases and iron, derived from volcanic ash. The particle size is probably under 0.03% of the average kaolinite grain. It is a very sticky clay with a high shrinkage and a tendency to crack during firing and cooling...but its super-plasticity can help short bodies such as porcelains. It also assists the suspension of a glaze. - p. 20, Illustrated Dictionary of Practical Pottery, 3rd Ed. by Robert Fournier
Volclay® began as volcanic ash millions of years ago. After weathering from rains and pressure by megatons of seawater, volcanic ash was transformed into what we know today as Sodium Bentonite. American Colloid Company processes Volclay® at locations in Wyoming and South Dakota. It is classified, dried, and sized according to type.
Volclay® is a high quality green sand binder accepted worldwide by the foundry industry. It is a foundry-proven product that provides the performance expected by today's foundrymen to meet the demand for quality castings. 
Volclay® is the preferred binder for production of green sand iron and steel castings. It is also selected in the production of copper base and aluminum castings when extra performance is needed. Because it is more durable than other bonding materials, Volclay® requires less replacement when sand mixtures are rebounded. 
Volclay® bonded sand mixtures also offer high, dry, and hot compression strengths to prevent sand erosion, cuts, washes inclusions, burn-on, and scabs.
Molding sand practic is based on having low clay content coupled with low temper water. By weight, only 5% of Volclay® added to 95% of unbounded silica sand is needed for quality base sand mixtures. It imparts excellent dried and fired strengths to molding sand where high temperature pouring occurs. Volclay's® unique capability to hold water prevents mold surface erosion by molten metal. It also provides excellent strength and toughness to molding sand mixtures, enabling good draw of the pattern.

13-T Features

  • Provides high tensile strength
  • Combats Friability
  • Excellent Dry and Hot Properties
  • Increases Durability and Toughness
  • Controls Expansion Problems
  • Quick Green Compression Strength Development
  • High, Quick Dry Compressive Strength
  • Intermediate Hot Strength
  • Low Viscosity

information courtesy American Colloid Company

Methylene Blue (meq/100g)


Soluble Calcium (meq/100g) <25
Green Strength (psi)

15 @ 7%

Moisture (%)


pH @ 6.25% solids


Liquid Limit 600-850