There are three kinds of binders commonly used in precision casting： Water glass, silica sol, ethyl silicate

In general, silica sol and ethyl silicate are used in the production of high precision castings. Among them, silica sol is a green binder, which is widely used. Water glass will be used in casting low precision castings. Silica gel is the binding agent of the three materials we introduced: silica sol, ethyl silicate and water glass binder. The main process is the gelation process from sol to gel and gel. Shell making is the gelation process from binder to gel and gel.

In the shell making, the particles with the size of 0 ~ 100nm are generally used. When the particles are of this size, the substance has a good bonding effect. However, with the passage of time, the particles gradually merged, which eventually led to gelling. If it is observed by naked eyes, it is reflected as the drying and hardening process of the slurry.