Imperial Green Opaque

[myrica]

Anyone else had problems with Imperial Green Opaque Asian boro?

It's probably me but every time I have used it with clear, it has cracked. I even had the bright idea of pulling two cracked pendants into stringer but the stringer turned into frit as it cooled. I'm cooling in bubbles and batch annealing. Maybe I should try putting it straight into a hot kiln?

[Steampunkglass]

I'd first check that the clear you are using is boro, as its more likely that a rogue rod of soft glass is causing the problem, if the stringer is going to 'broken bus shelter glass' when cooled I'd say that's most likely the problem.

Greens can be notoriously temperamental, some of the older recipes are based on chromium oxide, the chromium can sometimes cause problems where it produces areas inside the glass that are COE 54-55 which is why it cracks and why deep encasement is avoided. You can try mixing it with some clear to thin it down a bit, but I'd personally not both with any pendants that have already cracked. Popping it into a hot kiln for a more controlled cool might also help which is what I do with any more of the delicate glasses or things with more stress in them.

[garishglobes]

What he said!

I agree, if it's turning to frit like that I'd check the other glass around it. I have found in the past that the semi-opaque Asian glasses can be a bit shocky, but that's shocky on heating, which is a different issue. Once you get them melted, they usually work nicely. It could be worth putting into a hot kiln once done - maybe the glass just isn't coping quite so well with the cooling rate in bubbles.

[myrica]

Thanks guys. I'll try treating it a bit more carefully and see if that helps. Not been using boro very long and maybe I'm taking its abilities a bit for granted.

I cleared all the soft glass off my desk and even swept up (!) before unwrapping all the boro from Martin so I don't think any other glass has snuck in.