Mold Making

Mold Making Process- Getting Started

Shore A Scale

The Shore A Scale is an industry standard scale for measuring elastomers, or rubber materials. In this video we explain the Shore A Scale, the OO Scale, and the use of these measurements in choosing a silicone.

Platinum Silicone, such as 5130, is susceptible to cure inhibition. This means the silicone fails to cure at the pattern surface or through the entire mold. This happens when Platinum silicone formulas are applied to contaminated surfaces. In this video we explain how to test for cure inhibition and some ways to avoid it. For clay sculptures using Chavant NSP, we recommend sealing with at least 2 coats of Clear Guard followed by Zip 301 Mold Release.

Silicone molds must be released with a mold release that does not contain silicone oil. We recommend Zip 301 for mold-making applications such as silicone poured over glass, metal, or clay. Zip 301 also works for silicone to silicone release when making a 2 piece mold.

Rubber mold making is a vital skill to master if you plan on producing resin parts or any other cast part. The process is fairly simple provided you plan ahead and follow all of the directions. In this tutorial we walk you through the steps to make a simple platinum silicone block mold. This is the most basic of molds, but is also the most widely used for casting polyurethane casting resins. Block molds are ideal for reproducing small, simple parts and flat-backed parts.

Platinum Vs. Tin

Platinum silicones are the best option for accuracy and mold lifespan, but platinum formulas are also sensitive to cure inhibition. This means the silicone fails to cure and remains sticky where it came in contact with the incompatible surface. Common contaimantes for platinum silicones are sulfur, masking tape, some paints, polyurethane rubber, tin cure silicone, and aloe-vera. This is by no means a comprehensive list so it is always a good idea to run a small test before commiting to a large silicone pour.

Tin Cure silicone may be used to mold these surfaces and may also be preferable when mold object of unknown composition. Tin Cure Silicone, such as 5092, are much more forgiving. In this video we cover the basic use of our 5092. This is a ~25A silicone that is ideal for poured block molds. 5092 may also be thickened with Thixo for brush-on molds.

Some patterns are best molded with a brushed-on mold technique. This method is ideal for monuments, portrait busts, and mold applications where the finished mold must be light weight. This method trades material costs for labor costs. Brushed-on molds are more time consuming to make, but use much less silicone or other rubber. In this video we make a simple one piece mold using 5140 Platinum Silicone. 5140 may be thickened with Thixo for brush-on molds.

Some patterns are best reproduced in a 2 piece mold. A two-piece mold allows access to the entire inside surface as well as molding a part that doesn't have a "flat side" and minimizing undercuts. Typically firmer rubbers, such as 5130, 5140, or 5150 are used for two piece molds as they mate together better without distortion. Avoid very soft rubber such as 5100 or 5110 for two piece molds. Water Based Clay or Protollina Clay may be used to create a dividing wall.