Complete Guide To Silicone Molds

The Complete Guide to Silicone Mold Making and How You Can Use It For Your Own Projects

Introduction: What is Silicone Mold Making?

Silicone molds are used by companies and artists in a variety of industries to produce products that are made from various materials.

Silicone molds are used in the production of many different products, such as epoxy resin, candle making, toys, and automotive parts. They can be made of different types of silicone depending on the application.

There are two main types of silicone molds: positive and negative. A positive mold is one that has a cavity which will be filled with liquid silicone to create the final product. A negative mold is one that has a shape that will be filled with liquid silicone to create the final product.

Types of Silicone for Mold Making

Tin Cured and Platinum Cured

The main difference between tin-cure and platinum-cure silicone mold making rubbers is in the metal used to catalyze or cure the base silicone. Tin-cure rubber relies on traces of tin, while platinum-cure rubbers are based solely on platinum. As a result, tin-cure silicone rubbers usually cost less than platinum-cure ones.

Performance Differences between the 2 silicone types:


Mold-making rubbers can be inhibited from curing by contaminants on surfaces. If you’re using a modeling clay that contains sulfur (typically older types), the rubber may become sensitive and easily damaged. Platinum-cure silicone rubbers have a critical sensitivity to sulfur. If they are exposed to it, they will not cure at all. Tin cure silicones can cure over models containing sulfur as long as the surface is thoroughly sealed with an acrylic spray.


A major difference between these two systems is the shrinkage of cured rubber over a period of time – short term vs. long term. The long-term shrinkage is typically measured in percentages of the original thickness, but it can also be given as a percentage of the amount for which the rubber has been stretched. In short term tests, shrinkage was found to be only about 10% after two years; this would mean that at two years, a given sample of rubber would be 50% thinner Tin-cure silicone rubber molds generally exhibit higher shrinkage over time depending on the type of mold rubber being used, material being cast into the rubber mold, mold configuration, and other variables.

Mold Release Agents for Silicone Molds

Silicone-to-silicone applications such as making two-part molds or casting silicone into silicone are possible, but require a release agent. This release agent cannot contain a significant amount of silicone oil. Here are some release options:

  • Mann Ease Releaseā„¢ 200 is formulated specifically for releasing silicone rubber from silicone and other surfaces. Applied as a light mist coat, it will not interfere with surface detail.

  • A mixture of 2 parts isopropyl alcohol and 1 part dish soap can be used in some cases to release silicone from silicone.

  • Petroleum jelly can be used to release silicone from silicone, but it should be thinned with mineral spirits so that it can be applied in a thin layer with minimal visible brush strokes.

If you’re trying a new silicone recipe and want to be sure that your release agent will work, we recommend testing it at a smaller scale.

Silicone Mold Design Process

Silicone mold design process is a process of making a rubber mold from an object.

The first step is to create the silicone mold design. This can be done by using a CAD program or by using an object that you already have available.

Next, you need to create the silicone mold container. This should be a little bigger than the object to be cast. A simple method is to use foam board to create the container. For added ease of releasing the final product, you can coat the inner surfaces with Tyvek (available at the post office as waterproof mailing envelopes. Use hot glue to assemble your box.

Next, you will need to place your object to be cast into your container. You will need to lift it off the bottom of the container. In my example, I used hot glue sticks to lift the object off the bottom of the container. These will also be my pour holes to fill the mold.

Pour the silicone over the object in your container. Wait 24 hours, and remove from the container.

Removing the Object From the Mold

Once the silicone has cured, and the mold removed from the container, you will need to remove the object from the center of the mold. There are many great YouTube videos dealing with this topic. Here’s one that shows how to remove your object effectively. 

Once removed, you are ready to cast your piece using your new mold! Mix Puduo Resin and pour into the mold. Wait 10 hours and enjoy your custom piece.

Conclusion & Resources

Creating a mold is not as hard as it sounds. All it takes is a vision and a little work. As a beginner in mold creation, I was pleasantly surprised at how easy it was to create the mold. I used Translucent Platinum RTV-2 Liquid Silicone Rubber. Available HERE.

If you have any questions or comments, we are always here to help. Feel free to message us using the messenger button on the bottom right.


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