Everything You Need to Know About Casting Resin Molds

Casting resin molds are used for making a specific mold of an object you’d like to replicate or display. Resin is then poured into the mold in order to replicate the mold’s exact shape. This then makes a 3D object you can display wherever you choose.

Casting molds usually require a certain type of epoxy, more specifically, casting resin. This is also known as deep pour resin. This type of resin allows for thicker pours as it has a slower curing process.

Table top and coating epoxies, on the other hand, can be used for molds as well. Just keep in mind it will likely require multiple pours as usually they only allow up to 1/4 inch thickness per application. More on that here.

You can use casting molds to make just about anything! Many people make a mold to fill the resin and then submerge meaningful objects into the resin in order to preserve and display them. You can also make a replica of an object and spray paint it or add dye to make a beautifully artistic piece. In our YouTube video above, we used Let's Resin molds to create beautiful castings of various shapes. They turned out beautifully and you can see how crystal clear the Pourable Plastic casting resin is. One of my favorite uses for resin casting molds is to make Christmas ornaments! Fill the ornament with glitter, a snowman, or a family picture and then hang it on your tree for years to come!

Types Of Molds: DIY Or Pre-Made?

Casting resin molds can be purchased or made by hand. There are many types of molds you can choose from in order to suit your project. Flexible molds can be made of many different materials including latex rubber, silicone rubber, and more. Many casting resin experts use glass containers and leave their product inside to be enjoyed. This is a beautiful option that adds extra protection for your project. One of my favorite projects is using a small glass container to display some tiny objects and leaving enough room for a tea light on top!

If you choose to make your mold yourself, it is important to ensure you have all the materials you need before starting. You’ll need some casting resin, mold putty, the item you want to replicate, a razor blade or x-acto knife, and a timer. While most molds are made the same way, it is ideal to follow the directions on your mold putty box in order to properly use the product. When you begin to make your mold, you will quickly find that it turns into a putty or clay-like material.

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).

2 Part Mold Putty For Casting
  • Mix equal amounts of both colored-coded putties by hand (safe to touch) until no color swirls are evident (should take less than one minute) Note: no need to measure exactly – two portions of putty about the same size are close enough
  • Efficiently form the putty around the item to be copied – taking no longer than two minutes as the working time of mold putty is three minutes total
  • Let cure for 25 minutes and remove putty from object
  • Allow 24 hours for full cure, or heat-cure in a 350-degree F oven for a half hour
  • Voila – mold is ready for casting!

Note: While mold putty is food safe - once a mold is used for food - don’t use for anything else!

After you have your clay, you will mold the clay around whatever item you have chosen to replicate. Be sure to push the clay into the item filling all air pockets and evening out the clay. This is very important to ensure your mold won’t create any weird bumps or abnormalities on your finished product. 

casting resin molds

Then, you’ll let the clay sit and harden for about an hour. Keep an eye on your timer so you know when to continue the project. Next, you will use your blade or x-acto knife in order to cut through anything that folded over onto the backside of the item you molded. Be careful during this part. It is easy to slip and cut yourself or cut your mold in the improper place. Make sure you have a steady grip and think about every slice in order to make your mold exactly how you need it.

Then, very slowly and carefully remove the item you have just molded. Now you have your casting resin mold! You will then pour in your resin and follow the instructions on your product. After that, you will have a beautiful, replicated item from your very own mold!

If you are purchasing a mold, it is pretty easy to use. Be sure to read any directions on your mold first to ensure there isn’t a special treatment that your mold needs before pouring your resin. You can find molds in all different shapes from simple squares or globes to flowers, rings, chess pieces and more!  It is easy to find a very specific mold by simply Googling it. Sometimes, it is fun to simply look through different options for molds in order to get inspired to create a new project you’d never thought of before.

Resin molds come in a lot of shapes and sizes for many different prices. Most are pretty affordable with basic ones starting in a pack for around $10. There are also huge kits that come with tons of different mold shapes, pipettes, blades and more for about $20. You should be able to find the mold you need for a pretty small price. Obviously, you will find some that are more expensive and less expensive than these prices, but overall you can expect not to spend too much money on molds for your resin! However, it might cost less to simply make the mold yourself which is ideal if you already have an object in the shape of the mold you need!

There are many places to purchase casting molds as well as the product needed to make your own. Target, Hobby Lobby, Michaels, and Walmart all sell premade casting molds as well as casting mold putty. If you are looking for a very specific type of mold like an animal or car, then I would advise ordering online. Amazon and Etsy both have tons of options for casting molds available, enabling you to easily find exactly what you are searching for without wasting any gas!

Resin casting is a fun, unique project for all ages. While it can sometimes be difficult, it is very rewarding once you get the hang of it. It is a great way to preserve meaningful items or to simply try a new craft. Get creative, and make your own resin casting mold and project today!