AlginateA material found in algae, seaweed, and some bacteria. Most alginates used for molding are made from seaweed. When mixed with water they cross-link (similar to plastic) and trap the water into a moist, rubbery material. Over time the water evaporates and the material shrinks, hardens, and deforms.
CastingUsed as both a verb and noun. Casting, verb, describes the process of making a casting from a mold. Casting, noun, refers to the part pulled from the mold once the casting compound has cured. The part pulled from the mold is generally a "positive" part, exactly duplicating the original part molded.
HydrostoneA form of gypsum plaster, when mixed with water cures into a long-lasting, hard material without shrinking. This is slow setting, and pours well.
ModelThe person and/or object being molded.
MoldThe form for the casting, formed as a "negative" out of a molding compound which cured around the original.
Setting/curingUsed interchangeably in this instructable to describe the process a molding or casting compound goes through to harden.