How to make a two-part silicone mold

In this post we show you how to make a two-part mold to complete the copying process of a small original figure.

These double-sided molds are especially suited for copying complex pieces whose shapes would make it impossible to remove them from a single-sided mold. In this case, we'll use a saber arm piece as our subject.

Materials for making a two-part silicone mold

Here's a look at all the materials you'll need to carry out two-sided molding.

Silastic 3481 mold silicona

We use Silastic silicona with its corresponding catalyst. Its composition and materials support casting with different materials such as polyurethane resins, polyester resins, various types of acrylic resins, plasters, gypsum, and even Epoxy waxes.

Industrial plasticine

To make the mold we'll use 350 grams of industrial plasticine. It's a vegetable-based, non-toxic modeling clay.

It's reusable, doesn't dry out, and doesn't stain.

It's perfect for making molds and for use with various tools.

Ferosil V32 release agent

It's a petroleum jelly that makes demolding easier and eliminates pores caused by the silicona.

Epofer Ex610-A +E610-B putty

We'll use this product for the sprue of the piece. It's an epoxy putty for creating simple molds.

It dries quickly and is easy to use.

It comes in two components that must be mixed in equal parts. It works as an adhesive, as well as for filling and sealing metal surfaces.

The great thing about this putty is that it can be shaped with your fingers until you achieve the desired form.

It's important to know that this material works and molds very well with heat.

Other materials

In addition to all the materials listed above, you'll also need building blocks to form the walls of the silicona container.

Finally, you'll need a brush to apply the release agent, as well as a modeling tool.

Video tutorial for making a double-sided mold with silicona

Step by step: how to make a two-part silicone mold

Making the sprue

Take two portions of Epofer putty and mix them by hand to form the sprue of the piece.

Then shape the sprue with Epofer putty. It's a roughly conical application that will make it easier to pour the resin once the mold is complete.

Next, apply the release agent evenly over the entire piece using the brush.

Pay special attention to the putty sprue area to prevent it from sticking too much to the plasticine bed you'll be making next.

Making the plasticine bed

Now, using the industrial plasticine, make a bed onto which you press the piece you want to copy.

Once you have the shape marked by the piece, refine it with your chosen modeling tool.

Then place the piece horizontally, sinking it into the plasticine up to halfway.

This will allow you to define the molding line, since you need to seal all the plasticine buildup thoroughly to prevent silicona leaks.

Next, make a series of shallow marks.

In the same way, mark a perimeter channel around all the edges of the plasticine bed.

The purpose of the holes and groove is to help both sides of the silicona mold fit together and seal when pouring the resin.

Building the two-part mold

At this point, use the building blocks placed on a flat board. With these pieces, assemble the walls of what will be the silicona container and will determine the outer shape of your mold.

Then apply the Ferosil V32 release agent over the plasticine using the brush. Thanks to the properties of Silastic 3481 silicona, it's not necessary to apply it to the piece itself.

Applying Silastic 3481 silicona

You should always take exact measurements when mixing the silicona and catalyst, as otherwise the result may not be adequate.

In this case we'll use 800 grams of silicona and 5% of its weight in catalyst, which equals 40 grams.

At this point, mix both quantities together and stir thoroughly until both components are fully combined.

Use a 24-hour catalyst, which means that once mixed with the silicona it will take a full day to cure completely.

The working time will be 45 minutes, and after 24 hours you'll be able to demold the original. This way you ensure the durability of the mold, which you can estimate at between 30 and 35 very high-quality reproductions.

Then let the silicona dry for a few minutes, and proceed to pour the silicona and catalyst mixture into the mold.

We recommend doing this process from a certain height to break up the bubbles, and pouring from one of the corners slowly, trying to cover the piece with silicona in a calm and gradual manner.

Once the piece is covered with silicona, all you have to do is wait 24 hours for it to set.

Demolding

After a day, proceed to remove the building blocks and the plasticine.

As a tip, you can use alcohol to remove all remaining material.

Thanks to the recess made earlier, the edge created will help you fit the two mold halves together.

Apply a layer of Ferosil V32 release agent over the same formwork used before in order to seal the joints between pieces and prevent silicona leaks. It will also help to slide the mold over the formwork.

Now you need to apply the Ferosil V32 release agent across the entire silicona surface, since if you don't, the silicona you pour next will catalyze and bond to the previous side. This is a step you need to repeat as many times as necessary.

Creating the double silicone mold

As we did before, mix 40 grams of catalyst with 800 grams of silicona again. Repeat the pouring process exactly as before. Once the second pour is complete, wait the required 24 hours for it to cure.

Once the time has passed, proceed to demold and you'll see that thanks to the Ferosil V32 release agent, both sides of the mold can be separated without any issues.

Now you have your two-part silicone mold ready to produce perfect replicas, whether small and highly detailed or larger in size.

The best materials for molding and modeling, only at Feroca

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