The process begins by mixing a silicon-based liquid called "sol". Sol contains all the components for the chemical reaction that takes place after the casting process.
The sol-gel processing results in gelation of the liquid and the quartz glass components therein. At this stage, the gel is formed in the shape of the finished glass piece.
Shrinkage occurs in a subsequent multi-stage drying process where all the liquid components are extracted. In this stage xerogel, which is an open-pored silica skeleton, is created.
In the final sintering step, the part is thermally compacted into a solid amorphous quartz glass, remaining below the melting temperature. The original shape of the casting is thereby reduced down to 50% in edge length with high dimensional accuracy.