Silicone Molds

While latex must be brushed on an object several times to create a mold, silicone can be poured around an object. Using silicone to create a mold saves time and creates molds with greater tear strength, heat resistance, and longevity. Silicone is more expensive than latex, but for objects that have many undercuts and for projects that require many castings, silicone is the better mold material.  There are also some materials that can be cast into silicone that cannot be cast into latex, such as chocolate, candy, and even some low-melt metals. Before choosing a silicone for a project, always make sure it has the properties needed for your project. Depending on the project, you may want to consider the tear strength, heat resistance, pot life, cure time, viscosity, translucency, shore hardness, and whether or not it is food safe/body safe/ skin safe etc.

Key Terms:

Cure Time: Cure time is the amount of time it takes for the chemical process of curing to complete. Before casting any material, it is always wise to wait until the silicone has completely cured.

Pot Life: Pot life is the amount of time available to mix and pour the silicone before it hardens and becomes unworkable (also known as working time).

Tear Strength: Tear strength refers to a silicone's resistance to tearing. Silicone with high tear strength is much less likely to tear than a silicone with low tear strength. 

Viscosity: Viscosity is a measure of a fluid's resistance to flow. High viscosity silicone is a thick liquid that flows slowly. Low viscosity silicone is thin and flows quickly.

Shore Hardness Scale: There are multiple Shore Hardness scales for measuring the hardness of different materials:

"The Shore 00 Hardness Scale measures rubbers and gels that are very soft.

The Shore A Hardness Scale measures the hardness of flexible mold rubbers that range in hardness from very soft and flexible, to medium and somewhat flexible, to hard with almost no flexibility at all. Semi-rigid plastics can also be measured on the high end of the Shore A Scale.

The Shore D Hardness Scale measures the hardness of hard rubbers, semi-rigid plastics and hard plastics." 

(https://www.smooth-on.com/page/durometer-shore-hardness-scale Links to an external site.)

Types of Silicone:

Platinum cure- Platinum cure silicone can produce higher quality molds, higher chance of cure inhibition, more expensive due to the cost of platinum. Common materials that prevent platinum silicone from curing are 3D prints, sulfur based clay, tin cure silicone, polyurethane rubber, latex, and certain paints and adhesives. Products such as Inhibit X can be brushed onto an object to prevent cure inhibition.

Tin cure- Tin cure silicone typically costs less than platinum cure and is a more budget friendly starting choice for those who wish to learn how to use silicone. 

Caulk- Silicone Caulk is primarily designed for use in household repair projects such as sealing tile, glass, plastic, metal and more. 100% silicone caulk can also be used to make an inexpensive silicone putty for mold making. By pouring dawn dish soap in a bowl of warm water and kneading the caulk in the water with ungloved hands, the caulk can be made into a putty that can be pressed against an object to create a simple one part mold and to capture various textures such as bark, stone, metal, and more.

For more information about silicone, visit: https://www.smooth-on.com/ Links to an external site.

This image illustrates the process of pouring a one part silicone mold.