Smooth Cast 321

SKU: 796551

Size: Pint Kit
Sale price$35.20

unit(s) in Stock.


unit(s) in Stock.


unit(s) in Stock.

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* If unit(s) in stock is 0, item is currently unavailable or special order.


Unit Size Net Weight
Pint Kit 1.9 lb
Gallon Kit 15.4 lb
Five Gallon Kit 77 lb



Smooth Cast 321 is a medium-setting ultra-low viscosity casting resin that yields virtually bubble-free castings. Smooth Cast 321 Series resins yield castings that are off-white and are sister products to our popular Smooth Cast 300 Series of Bright White Plastics.
Technical Properties
Mix Ratio by Weight 100A:90B
Mix Ratio by Volume 1A:1B
Pot Life 9 minutes
Cure Time 30 minutes
Color Off White
Shore Hardness 70D
Mixed Viscosity 80 cps
Shrinkage 0.007 in./in.
Specific Volume 26.4 cu. in./lb.
Specific Gravity 1.05g/cc
Tensile Strength 3,000 psi
Elongation @ Break 8%
Compressive Modulus 40,300 psi
Tensile Modulus 138,000 psi
Flexural Strength 3,500 psi
Flexural Modulus 110,000 psi
Compressive Strength 3,550 psi
Heat Deflection Temp 140¼F


Smooth Cast 321 Series resins are easier to color and tint using SO-Strong color tints. Easy to mix and pour these resins offer the convenience of a one to one mix ratio (one part A to one part B by volume). The Smooth Cast 321 Series resins readily accept pigments and fillers (such as URE-FIL 3, 5 and 7 from Smooth-On). These products are ideal for creating cold cast metal effects. Fully cured castings are tough, durable, machinable and paintable. They resist moisture and mild solvents. Applications for Smooth Cast 321 Series resins include: reproducing small to medium size sculptures, cold cast bronze, making prototype models, special effect props, decorative jewelry, etc.
How do I remove release agent from my cured urethane casting if I want to prime or paint the casting?
Removing a silicone-based release agent from your cured urethane casting is not easy. The most effective way is to sand blast or bead blast the surface of your casting. However, sand blasting removes a micro thin layer of the castingÕs surface. If not done properly, you can damage or remove fine detail. Soap Wipe or brush the casting with a soap that has high alkali content. Cascade brand dishwashing gel is highly alkaline and also contains baking soda, which is an advantage. Solvents Wipe or brush the casting with Acetone, Toluene, Isopropyl Alcohol or Mineral Spirits.
Important: follow all safety precautions when using flammable liquids. You can then prime and paint your casting.
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