While each foundry customizes their shell system to best perform for them, nearly all shell systems in use fall into one of two basic types:
Fused Silica or Alumino silicate systems. Either shell system may be used successfully for QuickCast Patterns.
Fused Silica systems are designed to weaken after firing in the burnout oven. At temperatures above 1650° F the fused silica is crystallized into cristobalite. This crystallization weakens the shell and aids in the shell removal after metal is poured and cooled. The cristobalite conversion presents special challenges in the processing of QuickCast patterns and is discussed in detail in Part 4.
Alumino silicate shell systems are stronger and do not undergo a transformation at higher temperatures allowing them to be cooled to room temperature and reheated when the foundry is ready to pour metal.
Regardless of the shell type, or the base liquid of the slurry, QuickCast patterns can be and are regularly successfully shelled and casted. To our knowledge, no combination of shell system and slurry type has a higher probability of failure than any other.