Maybe a better approach would be to purify it by chemically dissolving the old glass in eg sodium hydroxide and reprecipitating it out.
I'm sure people have tried that though and it doesn't work for some reason.
I'm sure people have tried that though and it doesn't work for some reason.
Pretty sure the chemical reaction to actually dissolve glass is not particularly fast and I have no idea what you'd do to later precipitate it out, but it may not be an economically viable approach.