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Mold Making and Resin Casting

The 2 Part Mold

The 2 part mold requires a bit more planning than the single discussed previously. This mold is for any part that has detail on both sides, such as road wheels, figure parts or even whole figures and parts with heavy undercuts that would get locked into a one-part mold.

For this example, we will use a head from a figure that I have been meaning to make a duplicate of for practicing painting techniques, so no better time than now. You can see why a one-part mold would not work on this piece, as the chin would lock it into the mold. Sometimes you can get away with a single piece mold for a part like this if, for example, you only need a couple of pieces reproduced. If you pulled hard enough, it will come out! Forcing a part from a single mold like this would certainly result in tearing of the mold, maybe not the first time, but eventually.

Here is where we will need to construct a mold box. I use a few different materials for my boxes, such as particleboard, Plexiglas, styrene and even Legos!! (plastic building blocks)

We will use particleboard for this one.

The first thing you need to do when making a 2 part mold, is to decide on where to split your part. In other words, you have to use common sense here because you don't want a seam line running across some important detail like a facial feature. This is why on molded figures, you see the seam line running up the sides of the head as it is less conspicuous there and easier to remove. That is where we will put this one too.
Lets use a piece of acrylic for our base. When duplicating a hollow part, be sure to fill any open cavities that are not part of the detail to be molded (Fig 9).