Cristallo

Cristallo is a glass that is totally clear (like rock crystal), without the slight yellow or greenish color originating from iron oxide impurities.

The quartz pebbles which passed the selection process were heated to the point where the stones began to glow, then placed into cold water.

It was found to contain high and constant amounts of sodium and calcium carbonates, necessary to make workable and chemically stable glass.

By skimming the top of the molten glass, unreacted and undissolved chlorides and sulfates in the mixture were removed.

The process of remelting and placing the molten mixture into vats of water was repeated several times until the glass-makers were satisfied.

The batch then had manganese added to the mixture at this time, helping rid the cristallo of any color tints.