Degassing

Degassing removes trapped air bubbles from liquid resin or silicone before it cures, giving cast parts a smoother, more solid finish — useful for prop and armour makers.

When you mix a two-part resin or silicone, tiny air bubbles get stirred in. If they stay while the material cures, they show up as pits, voids or weak spots in the finished piece. Degassing pulls them out by placing the mixed liquid in a vacuum chamber, which lowers the air pressure until the bubbles rise and pop before you pour. Not every cast needs it: slow-curing materials, pressure casting, and pouring in a thin stream are common alternatives, depending on how detailed your mould is. Work in a well-ventilated space, wear nitrile gloves, eye protection and the respirator the product's safety data sheet calls for, and follow the manufacturer's instructions for the vacuum equipment. Degassing uses up part of the material's working time, so check the product's instructions before you start. Younger makers should work with an adult present.