re: Black glass.
We glassmakers believe there is not really any such colour as black. It is a deep shade of purple or blue when sliced very finely1
We made some wonderful black side plates with a pressed underneath and highly polished top face and some fruit bowls with indents for stones (for Nestle cream milk) with "tinker, tailor, soldier, sailor", over 300,000 in pale blue and about 250 in black so very rare now!
regards, Stephen