how hot does glass need to be to be anneiled?

Question

and is this really necessary? I wanted to make some goblets using reclaimed bottles. Will they be too fragile if I don't anneil them?

Answer 1

Here is a website that might help. It does show temperatures, but I do not what kind of glass you have, so I cannot give you a precise answer.

http://www.arrowsprings.com/html/annealing.html