Tin silicone (condensation) cures through a reaction with air moisture and releases a small by-product (alcohol) during the process, which causes slight shrinkage and limits its use with some epoxy resins. It is more affordable and perfect for getting started.

Platinum silicone (addition) cures without by-products, giving it greater dimensional precision, better tear resistance and a much longer mold lifespan. It is the choice for long production runs or when working with epoxy resins. The only thing to watch out for is inhibition: certain materials (sulfur-containing clays, cyanoacrylate adhesives, certain varnishes) can prevent it from curing properly.

Yes, as long as you use an alginate formulated for that purpose. Alga-Cast Slow and Alga-Cast Fast are tested and approved for contact with human skin. No release agent is needed — alginate does not stick to skin on its own. It is a good idea to lubricate any hair with baby oil so the alginate doesn't pull on it when demolding.

It depends on the size of the original and how you plan to use the mold. As a general guideline, between 8 and 12 layers is enough for small and medium pieces with a limited number of pours planned. For larger molds or production runs, it is recommended to apply 15–20 layers. Each layer must be completely dry before applying the next — typically 30–60 minutes between layers at room temperature, longer in humid environments. The last 2–3 layers can be reinforced with cotton gauze for greater dimensional stability.

It depends on the material of the original and the material you are going to cast. Silicone generally does not stick to most non-porous surfaces (plastic, metal, glass, treated wood) without any release agent. You do need a release agent when the original is porous (untreated wood, plaster, cardboard), when you are going to pour another silicone over the mold silicone, or when the original is already made of silicone. When in doubt, a thin coat of spray release agent never hurts.

For the shell mold (the rigid casing that supports the silicone mold) you need a hard plaster that won't deform under the pressure of the pours. EXADURO is the most common choice: it combines good resistance (1,300 kg/cm²) with controlled expansion during setting, which prevents it from deforming the mold. For shell molds that will see heavy use or require tighter tolerances, Arquero offers 5,000 kg/cm² and minimal expansion.

Yes, in fact it is one of the most common applications. Polyurethane rubbers for molds, such as Poly 74-45, offer abrasion and tear resistance that makes them ideal for concrete, plaster and filled material pours. It is essential to apply release agent to the original before pouring the rubber, and also to the mold before each concrete pour — fresh concrete can bond if this step is skipped.

In a block mold the original is completely surrounded by silicone or rubber poured inside a container (molding box). It is the simplest method and gives the mold more body, but uses considerably more material. In a brush-on or blanket mold the material is applied in layers over the original with a brush, building up a thin "skin" that is then reinforced with a rigid shell mold (plaster or fiberglass). It uses less material and is the right technique for large pieces or when the original does not fit in a box. For brush-on molds, choose a thixotropic material such as Polygel 35 — it won't drip on vertical surfaces.