Iris Yellow Frit cracking

[kmd]

HELP! Splitsville!
I just spent an afternoon making some beads using thick stringers made with large Iris Yellow frit, and Moretti light brown and light and dark topaz. The beads were made...................
1. over a white core encased with the topaz and the clear light brown and rolled in the frit.

2. Using a base of topaz or clear light brown, rolled in the frit.

3. OVer a base of white encased with light brown, and dotted liberally with the Iris yellow stringer. A very pretty bead using this technique was shown recently in the Show and Tell.

Everything looked lovely and I was quite pleased with myself, until I found a whole bunch of beads cracked right through .
HELP please.

KMD

[LyndaJ]

Can you please describe the cracks? Are they from top to bottom or only where the iris yellow is?

If they're top to bottom, that's typically thermal. The bead wasn't heated to a uniform safe heat before going into the kiln.

If the cracks are only around the yellow, then it's probably incompatability. Iris Yellow is Reichenbach with a COE~96. It only plays nicely with Moretti in very small amounts. Also, I've read that the reason we can get away with the small amounts is because of the lead content of the glass, and I've also read that the 95 COE glasses don't typically use lead in their yellows, reds and oranges. SO iris yellow may be on the edge of what you can work with.

[kmd]

I think it must be a bit of both. I used a LOT of frit, and then kept taking the beads out of the heat to see if the colour was developing. The cracks are right through, the bead in two pieces. I probably didn't heat them through properly afterwards. DRAT. the few that survived are still OK.

KMD

[kmd]

BTW. The beads went into vermiculite, I don't have a kiln.I make all my beads this way, and rarely have a whole bunch that cracks, just the occasional one.

KMD

[squid]

beads split in half are thermal cracks :(

[ChaseDesigns]

In this case it could be both thermal and compatitbilty