What can Bosporan glass tell us?
The Kerch Historical and Archaeological Museum has a collection of blue glass.
Blue glass is made from ordinary clear glass with the addition of 1% copper oxide. But at the same time, the CTE (coefficient of thermal expansion) changes, i.e. if you simply stick multi-colored glasses on top of each other, the structure will burst when it cools. To avoid this, the composition of the glass is changed, matching each other.
It turns out that far from the metropolis, local craftsmen knew how to make such complex things.