A lifecast is a copy of one or more live body parts constructed by pouring a castable medium into a mold. Lifecasting is the craft of producing both the mold of the body part, and the cast copy.
Lifecasting differs from other castings in both the delicacy of the target and in the need to keep the target relatively immobilized while making the mold.
Only skin-safe materials may be used in the construction of a lifecast mold. This excludes most resins, and any plasters that reach high temperatures during the cure process.
Casting materials depend on the mold used. Alginate molds leech water, preventing the use of polyester or polyurethane resins. silicone is used to produce quick lifelike props. Plaster is more common, as it works well with alginate.
Pieces cast from alignate often have flaws. To overcome this, a cast piece, called the "positive" may then be carved and altered using dental tools, clays, and filler putty. A reusable mold is made of the positive using whatever mold techniques and materials are desired. Any number of "corrected positives" may now be made from this mold.