As early as middle 17 century,people had already invented a sodium silicate water glass binder that with both true solution( sodium silicate dissolve in the water which existed as molecular state) and colloidal solution. When it comes to 19 century, people had also invented that blow CO2 gas could harden water glasses. However,until much later than 1950,water glasses as binder of mould and core sand were wildely spread in casting workshop.Main reasons of that result are as belows:

Water glasses have full resources of raw material with a low price; during the mixing、modelling、pouring process, water glasses sand would not produce a noxious gas or give rise to a black pollution,which had become a great sand binder for cleaning or making moulds and cores;casting sand are not included N、S、P element and showed plasticity under high temperature,which applied to pouring steel casting parts and large iron casting parts.

Water glasses sand technology, which are used in foundry production right now, divided into 3 ways by different hardening methods: CO2 method、ester hardening method and VRH-CO2 method.