My last glass order had some non-boro mixed up with the Boro. It looked lovely when it went in the vermiculite. Here are the results.
Suspect it was Effetre.
(One tap and it fell to pieces.)
(http://runnyglass.co.uk/stus/P7030781.JPG)
ahhh what a shame... its a bugger that it isn't stable as its actually a really pretty effect!
I had the same thing a while ago when I used a boro punty on a soft glass piece and didn't remove the punty properly. It was pretty well welded on so I had to flame cut it. I thought I removed all the boro with pliers after but when it came out of the kiln the top was all crazed....
Thats a shame......
I got a non-boro stick mixed in once, but was lucky enough to realise before I used it. I pulled a stringer and the glass was so drippy it rang alarm bells!
I also bought some supposedly boro test tubes on ebay about a year ago and used one as a core for a heart. It was a central band running right through the piece, but amazingly, although it all crazed, I still have it intact, held together by the boro on either side.
I'm really bad for this, I have a few designs with incompatability as part of it to make little bands of crazing inside the piece, so far it's been heavily contained enough in boro to remain intact, but I quite like the reduced life expectancy of such a piece.