Release agents are materials that allow you to separate cast objects from molds. There are two categories for most release agents: barrier and reactive (or chemically active) types. Barrier release agents work by forming a barrier between the form (the cast) and the mold. Paraffin wax is an example of a barrier release, as is Al-Cote,® which I explain in the next section. Chemically active release agents are releases that have an active ingredient that is usually some type of fatty acid, such as soap, that is dissolved in some sort of a carrier, such as alcohol (e. g., Tincture of Green Soap).
Sealers are liquids or sprays that are absorbed into porous surfaces to seal against moisture, making the surface essentially no longer porous; they can act as both a seal and a release for some materials. Not all materials need to be sealed and/ or released, though for some applying a mold release will make demolding easier and will most likely prolong the life of the mold. A comprehensive listing of suppliers for releases and sealers is included in the appendix at the back of this book.