Most new to casting like to start with Polyester Resin (PR) such Castin' Craft, which is readily available in your local hobby store and can be purchased in small quantities. PR is also available online in larger quantities through manufacturers such as U.S. Composites called Silmar 41. Polyester Resin does not require a pressure pot to create great looking pen blanks, but it smells very strong and can shrink away from other materials as it cures, so it takes some practice to get good at using it for pen blanks. We often times use it for clear casting materials that have been glued with Mod Podge or other water-based adhesives. Polyester Resin casts well in any of our molds.
Another popular material more experienced casters like to use is a Urethane Resin called Alumilite Clear, available in your local hobby store, directly from Alumilite, or distributors such as Curtis Seebeck at Turn-Tex. Urethane Resins have a shorter set up time than PR, so it requires experience with a pressure pot to reduce surface bubbling. We make many of our color swirls and hybrid blanks with these resins. Alumilite has dyes and powders to add to the resins and offers a volume calculator to help determine how much resin is needed per mold dimensions. Urethane Resin casts well in any of our molds.
West System, Liquid Diamonds Epoxy, Alumilite:
In early 2017, we introduced the blue molds to meet the needs of Epoxy casters, who prefer to use resins by West Epoxy System, Liquid Diamonds, Alumilite's Amazing Clear Cast, or Alumilite's Amazing Casting Resin. From what some of our casting community have said, Epoxy shortens the shelf life of the pink molds, so we recommend using the blue molds, which is made from a silicone material designed for epoxy usage. You can also cast Polyester Resin and Urethane Resin, so it's a better multi-purpose design for all types of resin casting.
A Universal Mold Release such as Stoner helps to extend the normal 5 year shelf life of silicone molds. If you cast with Epoxy Resin, Stoner also makes a Thermoset mold release specific to epoxy resins.