Series index for silicon rubber mold-making tutorials. See the updated mold-making guides.

Frequently Asked Questions

What topics does the Silicon Rubber Mold Making series cover? The Silicon Rubber Mold Making series covers material selection between platinum-cure and tin-cure silicones, mold box construction using LEGO bricks or melamine boards, parting line planning, clay bed preparation, two-part block mold pouring, and advanced techniques including glove molds and multi-part molds for complex undercuts.

Which silicone rubber is recommended for prop mold making? Platinum-cure silicone (addition-cure) is preferred over tin-cure for prop mold work because it has zero shrinkage, superior tear resistance, and longer mold life. Smooth-On MoldMax 20 (Shore A 20) is the most commonly used product — it is flexible enough to release complex shapes while maintaining enough body to hold its form during casting.

How is a mold box constructed for silicone mold making? LEGO bricks have become the standard mold box material in the prop community because they interlock precisely, create leak-resistant walls without adhesive, and can be built to any footprint in 8mm increments. Melamine-coated boards hot-glued together serve as an alternative for larger masters that exceed practical LEGO dimensions.

What preparation does a master pattern require before silicone is poured? Porous masters must be sealed with two to three coats of spray lacquer or Smooth-On Smooth-Prime urethane primer and allowed to cure overnight. After sealing, a thin coat of petroleum jelly or Ease Release 200 is applied with a soft brush and excess wiped away, leaving only a thin release film over all surfaces.

Further Reading from Authoritative Sources

  • silicone rubber — Wikipedia’s silicone rubber article provides authoritative coverage of both cure chemistry types, Shore hardness ratings, and material properties that determine which silicone is appropriate for a given mold.
  • mold making — Wikipedia’s Molding (process) article provides authoritative context on mold design, parting line theory, and production principles that the silicon rubber series is built around.