How to Make Silicon Moulds and Cast With Resin



Introduction: How to Make Silicon Moulds and Cast With Resin

About: I love making things.

For this project I used Art resin, Super Sculpey clay, Sculpey Bake and Bond, aluminium wire, tinfoil, sandpaper, scales, a plastic cup and silicon.

In this instructable I will be showing you how to make a two part silicon model for simple sculptures and objects without too much expensive equipment.

If you would like to see me making the original dinosaur head and casting it you can visit my YouTube channel -

Step 1: Box for the Silicon

You can make the box out of anything from plastic to thick card. Here I am using card and cutting it with a sharp craft knife. When using a craft knife make sure to have a cutting mat underneath and use a metal ruler when cutting.

TIP: To hold the box together I like to use electrical tape as it is waterproof and stronger than sticky tape.

Step 2:

If your model has a base that has no detail on it, this makes it far easier to cast. This is because instead of propping it up in the silicon, it can just be mounted to the side.

As you can see in the image, I use a drill and wooden sticks to secure the model in place. Make sure to leave space above and below your object. Ideally your object should be horizontal along its line of symmetry. However your object doesn't have to be symmetrical, it's just to make sure each half of your mold has equal amounts of your object in it.

Step 3: First Layer of Silicon

Once the first layer of silicon has cured (which takes approximately 15 minutes) I use a mixture of Vaseline and white spirits, which helps to thin the Vaseline. All this does is prevent the next layer of silicon from sticking.

Something I learned when making this mold was it's a good idea to add holes for the next layer of silicon to grasp. In other words adding holes to the surface so each half of the mold interlocks.

Step 4: Second Layer of Silicon

Reseal your box and add the next layer of silicon. Make sure to leave at least a centimeter between the top of the mold and the object to give your mold more strength.

Step 5: Removing the Object

Next you have to remove your object from its mold. In my example it shows small fiddly things (teeth) may end up breaking when you take your mold apart. However if you are not worried about your original object this isn't much of a problem as your mold will still replicate the original.

Step 6: Mixing Your Resin

You could say this is the most important step. Since I am using Art Resin, it requires a 1 to 1 ratio which I measure out with scales. After that, thoroughly mix the resin at room temperature for 3 minutes. Once you have mixed your parts A and B of the resin, you can add your dye or paint.

There are a few ways to prevent bubbles but if you are adding dye or paint that isn't clear, it doesn't really matter because you can't see them. To get rid of bubbles, you can mix slowly, pour slowly, use a pressure pot or use a lighter to heat the surface, causing the bubbles to rise.

Step 7: Pouring the Resin

Finally pour your resin into the mold. To secure the mold, you can use rubber bands but make sure they are very tight. Art resin seems to cure after about 10 hours, but there can be exceptions.

Step 8: Finished

I have used this mold multiple times as you can see, but the one thing that would make it better would be to have notches in either side of the mold as I mentioned earlier to make sure the two halves match exactly every time.

I hope you have lots of fun making molds yourself!

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