Does some glass crack easier than others?

[cherylsart]

I made some of the beads that have transparent glass on one half and ivory on the other. The beach/ocean look. Anyway, I often get cracks along the hole on the transparent glass. This was vetro aqua. It seems to me that the transparent cracks more easily than the opaque. Now I am batch annealing, and this crack developed after I took the bead off the mandrel, before it was annealed.

So my question is this: Is some COE 104 glass more susceptible to thermal cracks than others?

Thanks!

Cheryl

[tiggybubba]

Some dont hold the heat as well as others.....and therefore cool faster.

[alexm]

Yes. I have made a lot of beads like that and I've found that the transparent blues and aquamarines are more prone to thermal cracking. The darker the color the worse it is. I never use cobalt on these beads any more, it always cracks. The other colors are ok as long as I put the beads directly into the kiln, as opposed to batch annealing.

[LyndaJ]

Anybody know why they don't hold heat as well????