Although different clays have different densities a good estimate is 90 pounds per cubic foot. AutoStyle™ Industrial clay is light weight (approximately 30% lighter)
Concerns with mixing different clays are color, reactions to rubber, hard/soft areas and cohesion. A user may hit firm areas and then soft areas when moving tools through the clay. Proceed with caution.
Try water, Avon Skin-So-Soft (Original Bath Oil), WD-40, Goof-Off, turpentine, lighter fluid, multipurpose oil/wax solvents, Citrus/ D-limonene based cleaning fluids
Sulfur is an inexpensive, non-toxic, soft mineral filler that enhances the surface texture of the clay.
Sulfur free formulas are generally easier to make silicone rubber molds from
Heating some Chavant clays in clay warming devices, often required to soften the material, can produce a distinct non-harmful odor. Many clients have successfully reduced odor emissions from clay ovens by attaching activated charcoal filters to an exhaust vent often found on ovens.
Activated Charcoal (aka Activated Carbon) Filters are available from various manufacturers. Check the Thomas Register under Filters: Activated Carbon. One model that we have seen is produced by Airfiltronix Corporation of Clifton, NJ. They can be reached at 1-800-452-8510 or through their web site www.airfiltronix.com.