Poured Block Molds
Block Molds
The most basic type of mold is the poured block mold. In this first tutorial we explain the planning and rubber selection process of a seamless block mold In this tutorial we use 71-10 to create a fast, stretchy, 1 piece mold. Sadly, since we made this video, 71-10 has been discontinued. PlatSil FS-10 has taken its place and is a much stonger, easy to use formula. You can find FS-10 and other PlatSil formulas here.
For delicate resin casts or wax patterns, it is a good idea to make your mold with a soft silicone formula that can easily, and gently, pull around deep undercuts. In this tutorial we mold a skull face with deep undercuts using Skin Cast OO50 silicone. Once cured, we also pour an ArtKast Translucent positive pigmented with PolyPig colors to have a natural bone color.
Tin Cure silicones, such as 5092, make excellent block molds. Tin Cure formulas are preferred when molding patterns that may inhibit Platinum silicone formulas. In this next tutorial we explain, in detail, all the steps for configuring and planning and casting into a basic block mold.
A two piece block mold may be required for more complicated patterns. In this video we mold a pipe wrench using 5140 Platinum Silicone. 5140 is a firm silicone formula that is ideal for 2 piece molds and foam casting. We used the finished mold to cat TC-284 Flexible Foam props. We released the pipe wrench with Zip 301 Mold Release and the clay was Water Based Clay.
Many poured molds using silicone will need to be vacuum degassed. In this tutorial we discuss the vacuum degassing process as we pour a simple block mold. The mold in the video was released with Eject-it 33 release, poured in a 12"x5" mold tube, and TinSil 80-15 was used for the silicone.
In this next tutorial we mold a MothMan cryptid figurine and discuss mold configuration as well as material selection. For this mold we used 5092 Tin Cure Silicone with Yellow (Medium) Catalyst. At the end of the tutorial we pour up a Mothman using ArtKast Tranlucent resin pigmented with PolyPig Brown.
For more complex parting lines, a firmer silicone is preferable. For this 2 piece horse mold with a slightly more complicated parting line we used the economical P525 Platinum silicone. P525 is a 1:1 ratio, very low viscosity formula that is ideal for inexpensive block molds. P525 cures to a 25A and has a ~15 minute working time and a ~3-4 hour demold. While this is a good inexpensive option for simple molds, we recommend PlatSil 73-25 for more robust, production molds.
Veneer stone is typically cast from a block mold. For large molds for concrete, urethane rubber is preferable as it has a much higher abrasion resistance than silicone. In this tutorial we pour Poly 74-20 into a master mold made of Poly 75-80. This video explains how to make a master mold for reproducing veneer stone molds for mass production. 2300 mold release is ideal for releasing urethane rubber from many surfaces. Polyurethane rubbers are very adhesive!!!
Some resin parts may require multi-piece molds or molds with vents and sprues to allow for better flow of EasyFlo or 1512 resin through the mold.
In this two part tutorial we show how a 3D print is broken down into sections and molded in three PlatSil 73-25 molds all cast in EasyFlo resin.
In this next tutorial we use a very soft silicone to mold a complex shape and minimize seams. We used Skin Cast OO30 for this mold, but If we were to make it again I would opt for a little firmer TC-5110 or OO50. We cast up the finished part in ArtKast Translucent pigmented with PolyPig colors.
When casting thin parts in EasyFlo Resin, vents are crucial to achieving consistent, bubble-free parts. In this tutorial we address venting of complicated parts using TinSil 80-15 silicone and EasyFlo resin.
2 Piece molds may also be created using the block mold method. In this tutorial we make a 2 part mold of a model car body. To make a fast mold that would hold up well in production, we used PlatSil Gel-25 for our silicone mold rubber. 2350 was used as a release.
Molding & Casting Scale Model Parts
In this video we use PlatSil 73-15 silicone to make a block mold of a model airplane propeller. We released the original part with 2500 spray release and cast it up in EasyFlo 60 casting resin.
In this next video we make a cut block mold with TC-5130 Platinum silicone. This is a knife mold prop and we made several vents in the mold to allow resin to flow out through the mold and air to vent out. TC-5130 is a great 1:1 ratio 30A silicone for cut block molds.
In this video we make a candy mold for custom candy pops using PlatSil Gel-25. This is a quick overview of the process of using a food-safe silicone to make candy molds. If you need a food-safe silicone with a longer working time, consider PlatSil 71-25. We used Protolina Soft to sculpt the candy shapes.