We often have to reproduce broken "slag" glass petals for lampshades and have used steel, sand, porcelain, hot glass mold mix, and several other things to make the molds for the petal-shaped pieces. Through a conversation this morning I mentioned that I would reach out to see if anyone had any information on the techniques that the studios used back in the turn of the century for slumping the stained glass after the lampshades progressed into using the cheaper, readily available stained glass instead of actual slag glass.
I am imagining a detailed mold making book from the 20's and wishing it was something someone has in a stack somewhere waiting to be shared!
Any help, discussion, or information would be welcomed! If you would like to contact me directly my e-mail is email@example.com