I've been offline for a few days with HDD problems and a note from Adam A. has brought me back here. Sorry, I never heard the term teeming in connection with glass in my little corner of the industry, except when the rain was coming through the roof!
Using the word as in "pouring", a wild guess is that it might have been used in early making of ground and polished plate glass, where a large pot was poured on to some form of iron plate before rolling. That would, in the UK, be Pilkingtons and they used words which no one else did.
Frank, I'm impressed that you have Hodkin & Cousen. When I was a student that was the only decent text book in English but it was long out of print even then and was unobtainable! I think we had one library copy.
Adam D.