Everything You Need To Know About Casting Resin Molds

How to Make Molds for Epoxy Resin Casting

Casting Resin is frequently used for encapsulating objects and in crafting furnishings such as river tables. To encapsulate objects, a mold is used to hold the epoxy resin and the items to be preserved. Silicone molds may be purchased at a variety of hobby and craft stores however, the selection of shapes and sizes may be limited. So, many artisans and crafters custom design their own epoxy resin molds to suit their unique artistic vision and task…

Silicone Mold Putty vs. Liquid Silicone

There are two ways to create DIY Resin Molds that we’ll outline here; using silicone putty and liquid silicone. Silicone is used for epoxy resin molds as the polymer doesn’t stick to it. There are, of course, pros and cons to both methods. Both materials, however, involve making a negative mold of an object – to then fill in with epoxy resin (once the mold has cured and the positive object removed) to create the finished piece(s) desired. Let’s take a closer look…

Making a Mold of Liquid Silicone

There are two methods of DIY mold making with liquid silicone; using a kit designed specifically for the purpose or creating one’s own casting molds using a tube(s) of silicone chalk. Liquid silicone mold-making kits, like silicone putty, are two-component systems that are mixed in a 1-to-1 ratio:

• Mix equal parts of Parts A & B in a plastic cup & stir thoroughly for five minutes
• Place item to be copied into a plastic (non-silicone) container with enough space for mixture to cover item Note: working time with mixture is about 30 minutes
• Let silicone cure for 6 hours at room temperature Note: minimal shrinkage will occur
• Once cured, remove item(s) from mold(s) – molds are ready for epoxy resin casting!

To create epoxy resin casting molds using silicone chalk, items needed also include a bowl of water with liquid soap mixed in, (using about 1 part soap to 10 parts water), and of course the item from which you want to create the mold. (Hint: if you use colored liquid soap, it will make the mold creation process easier as you can better see the silicone chalk in the water.)

• Squeeze the silicone chalk into the bowl of water in the desired amount needed to cover the object becoming the mold
• After putting on plastic gloves, form the silicone in the water into a ball then knead as one would bread dough until it is no longer sticky - about five minutes
• When the silicone begins to harden a bit, it is time to remove and mold around the “positive material” being used to create the mold – ensuring as watertight a seal as possible
• Let cure for an hour or two until the mold is no longer tacky to the touch – then gently remove the positive item
• The mold is now ready to receive epoxy resin for casting!

Note: Liquid silicone is not made to be placed into ovens and is generally not food safe.

Making a Mold using Silicone Putty

Silicone rubber mold putty comes in a two-part kit containing two types of putties that are combined in a 1-to-1 ratio to create a mold. Unlike liquid silicone, mold putty is food safe and may be heated in an oven to approximately 400 degrees F depending upon which putty kit is selected (check the instructions for exact temperature tolerances).