The evolution of alkaline raw materials used in glassmaking follows very closely the evolution of industrial chemistry since the end of the XVIIIth century. After the necessary purification of natural soda ash due to market requirements for a white glass, the French revolution and the the following events accelerated the transition towards synthetic sodium carbonate produced by the Leblanc process during the XIXth century. The cost of this raw material induced glassmakers producing non-white glasses like bottle glass to use either the old impure materials or mixtures of sodium chloride and sodium sulphate, precursor of sodium carbonate in the Leblanc process. Sodium sulphate itself was widely used in plate glass factories when it was understood that the colouration it produced in glass was due to iron impurities and could be removed by a chemical process.
