PDA

View Full Version : Cracking Up!


amealer
08-06-2004, 01:27 PM
These are the end results of time spent on the torch last night. I used Moretti glass for three of them, stained glass scraps for the upper left and right, and Bullseye for the lower center one. In general, I like the beads; but the top three were cracked down the mandrel line when I took them out of the vermiculite this morning so I'm trying to figure out what happened. I used the same techniques with them as the lower three: used a 3/32" mandrel with a Hot Head, I left at least a mandrel width of glass above and below the hole, and they cooled in the same bucket of vermiculite as the other three. I'm using a pair of small "ice tongs" from Target as a bead masher (works pretty well...). I'm wondering if maybe I let the cracked beads cool too long before putting them in the vermiculite? Any input would be appreciated!

Thanks,
Allen

Onalee
08-06-2004, 02:59 PM
Allen, another thing that will crack them is to get them to close to another bead that is cooling in the blanket. I have the best luck tho just sticking them straight into the kiln. Less shock with temperature change. Onalee

CalmWaterStudio
08-06-2004, 03:06 PM
Allen...

I'm with Onalee... that's the best way to avoid that kind of shock.

I know lots of people swear by vermiculite, but, I have more beads crack using it than a thermal blanket. I'm not sure why some people use it with such success, and others not... but, I'm definately in the NOT category. If I'm going to batch anneal , I use a fiber blanket instead and lose very few beads to cracking.

Those beads look like thermal shock to me And, that's too bad... they're very pretty beads that look time intensive. Thick Moretti beads are bad for that. One lady that took a class from me even swore that the air conditioning setting in her house caused Moretti to crack when others didn't. (...not sure about that one!!) Those cracks down by the mandrel channel... they can also happen while you're making the bead if you get the bead a little cool... say to apply stringer or dots... and then pop it back into the hot part of the flame too quickly. I've had my share of those in the past also.

Good luck... your beads are very pretty.

AlexM
08-06-2004, 03:55 PM
I suspect that you let them cool too much before putting them in the vermiculite. Size is another thing that comes to mind, the bigger the bead, the more risky it is in vermiculite or with a blanket. I don't know what size those were, but that may be a factor. Another thing that might contribute to it is the stained glass. Not all stained glass is compatible with one another, even from the same manufacturer unless it says fusing compatible.

crsann
08-06-2004, 04:15 PM
imo the reason they cracked is def thermal shock because of squishing them you made the amount of glass nest to the mandrel wayyy thinner thatn the other thus it cools down much faster sooo shock.
chrisann

Smedstad
08-06-2004, 04:19 PM
imo the reason they cracked is def thermal shock because of squishing them you made the amount of glass nest to the mandrel wayyy thinner thatn the other thus it cools down much faster sooo shock.
chrisann


This was my reaction as well. You may have squashed them too thin. If you have beads in this shape that are this thin and have not cracked, you may find that they split in half when you try to remove them from the mandrel. Someone else may know the rule of thumb for how thick the glass needs to be around the mandrel. Also, a fiber blanket MAY work better than vermiculite until you are able to get your kiln.

Debbie

firemonkey
08-06-2004, 04:23 PM
Are you reheating the bead back to a soft glow after you mash?
I use the Target tongs also and I always reheat to get rid of the chill marks and to even out the heat before I place in my fiber blanket.
Hope this helps- let us know...

amealer
08-06-2004, 04:39 PM
Thanks to all who have made suggestions and complimented the beads. I appreciate the input. I'll try to incorporate the suggestions next time I'm on the torch. I've purchased a used kiln for annealing but it hasn't yet arrived. I'll still have to batch anneal, but that will be better than my current situation. But the price was right....

Thanks,
Allen