Slushcasting is a technique wherein you rely on the adhesive properties of a casting substance to create a hollow shell replica from a negative mold. A small amount of the casting substance is poured into the mold. The mold is then rotated or "slushed" around so the casting medium clings to the walls of the mold. Depending on the viscosity of the medium, care must be taken not to create airbubbles. The substance then cures or dries and the process may either be repeated for added thickness, or the prosthetic may be pulled as appropriate for the desired effect.
Latex is probably the most popular substance used for slushcasting, though many other materials are able to achieve results from this technique.
Compared to other casting methods, this technique often requires less equipment and cheaper materials. This makes slushcasting an excellent tool for beginners.
Slushcasting is also used to skin a mold. Slushcasting the first layer of a mold can generate a more lifelike appliance, especially when casting foammed substances, as it aleviates the worry of pin-hole surface defects from airbubbles. It also alows the skin to have a different makeup than the underlying "flesh" of a prosthetic, which thereby mimics real life.
Slushcasting is not without its downsides. Because the technique utilizes a single plane, it cannot be used to produce sections of varying thickness. The medium will tend to pool in cavities unless the mold is in constant rotation on multiple axes. Building up a thick shell in the casting medium will heavier than using a foam, which is interspersed with air. And because the thickness is not bounded, one can easily make a prosthetic too thick, distorting over the original substnace, or too thin, creating a hollow cavity that must either be filled or treated with care. An example of this situation would be the clown nose, which is tweekable due to it's hollow nature (not to be confused with a foam rubber clown nose, which is tweakable because it is an open-celled foam)