Note 274 — Chapter XVIII · (XXXII.)
Louisa S. Maclehose translation
It will be understood that the glass subjected to this treatment is not coloured in the mass, or what is called ‘pot-metal,’ but has a film of colour ‘flashed’ or spread thinly on a clear sheet. This is done with certain colours, such as the admired ruby red, because a piece coloured in the mass would be too opaque for effect. Economy may also be a consideration, as the ruby stain is a product of gold.