I see...
Of course they hadn't boro-silicate glasses and they must pay attention to the temp. jumpies to avoid cracking and breakings: they worked with normal glass or gress and for this reason they had some particolar lutum just to stick together the parts of their glasses.
And so it means, of course, that it was a normal glass with an open shape: You won the prize AB!
...One interesting thing is that if I search
sugar glass on Ruesenstein appear only one amswer but if you search only
glass you'll find a lot of answers.
It means that pdf doesn't work properly with these typewriter letters and a word like
sugar has an "r" that's always different.
Anyway. Have salty days bros.!
Zosimo