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Tips, Techniques, and Questions -- Technical questions or tips |
2012-12-19, 9:12pm
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Junior Member
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Join Date: Oct 15, 2012
Posts: 4
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thermal bead cracks due to studio in basement?
We are new to lampworking. We are having trouble with beads cracking before they are annealed. What may be causing this and how can we keep it from happening?
After doing some reading, I'm pretty sure they are thermal cracks. They are right down the middle of the bead. My daughter is working in an unheated basement, due to space and safety concerns. She has an electric heater, but it still cold down there. Could this be the issue? If so, what options do we have?
Thanks!
Marla
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2012-12-19, 9:18pm
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Senior Member
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Join Date: Jul 18, 2007
Posts: 568
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What is your daughter you doing with them directly after making them? If they go from flame temperatures to just room temp, it doesn't matter much whether it's 30 degrees F or 100, because it's potentially dropping a whole 2000+.
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2012-12-19, 9:19pm
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....uhm...
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Join Date: Sep 24, 2012
Location: Texas
Posts: 1,155
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Maria, are you batch annealing or do you put the beads right into a kiln? If you are batch annealing what do you put the beads into while you wait to anneal them?
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2012-12-19, 9:28pm
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Slogan Challenged...
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Join Date: Mar 21, 2009
Location: Maricopa, Arizona
Posts: 6,286
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Hi Marla.
Options include a thicker fiber blanket if she is using one. I don't know if it matters you heat the vermaculite in a crock pot. The size and shape matter. I find thermal cracks occur more often with larger, pressed or sculpted beads with different size parts. A good rule of thumb is the glass on either side of the bead should not be thinner than the width of the mandrel, or there will be thermal cracks.
Flame annealing will definitely help. This means you even out the heat through the bead by "soaking" it at the tip of the flame for a minute or so. This is not proper annealing, and you will still need to do that, but this will help the bead cool evenly and hopefully prevent cracking.
Edited to add : yes, definitely use something to place the bead into if you are batch annealing later.
HTH
--------------
Kristin ~
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2012-12-19, 9:31pm
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Senior Member
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Join Date: May 27, 2008
Location: Albion NY
Posts: 517
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What ventilation do you have in the basement.
Are you useing fiber blanket or vermiculite to slow down the cooling?
Do the beads have overly thin spots?
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2012-12-19, 10:34pm
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Junior Member
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Join Date: Oct 15, 2012
Posts: 4
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Thank you so much for all of your replies and ideas! It is so appreciated.
Part of the problem is we don't own a kiln (yet) so we bring them to her teacher's kiln when we get the chance. As soon as my daughter completes a bead she puts it in a fiber blanket. Just as she does in class, where the beads are placed in a fiber blanket for the instructor to bring home and anneal later. With her class beads,cracking hasn't been an issue (but she has only done round beads in class, so the different shapes she does at home may be the problem, along with extreme temperature changes).
Another issue which is a possibility is she is making different shaped beads, like octupi, snowmen, and horses. She's only been lampworking for a couple of months and is very new to it, so this may be a problem, as kjohn mentioned. I'll also mention the flame annealing to her as well.
For losthelm, I built her a ventilation system out of foam board, aluminum tape, and a greenhouse fan that was 720 CFM. I bought the beginner's bead kit from Howacoglass.com that has a small hot head torch. For Dusty, Dawn and losthelm, we use a basic fiber blanket to cool the beads down. They are later batch annealed at my daughter's teacher's house. I don't think the beads have overly thin spots, but they are not just round but different shapes.
Thanks for your time and expertise.
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2012-12-19, 11:44pm
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....uhm...
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Join Date: Sep 24, 2012
Location: Texas
Posts: 1,155
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I always find it better when doing sculptures to put them straight into a garaging kiln...since there are different thicknesses to the glass, the thinner parts will cool down so much quicker than the thicker. And with how cold it is in the basement, even with the fiber blanket it's probably cooling too quickly. It might be better for your daughter to keep making round beads instead of sculpture until you get a kiln. Although there are folks here with way more experience than me that may have ideas to keep sculptures from cracking until you can anneal.
I have to add, that if you have a kiln, and garage while torching...it will warm up her area very nicely. At least mine does. It was really hot when it was warmer...it's pretty darn nice now.
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2012-12-20, 2:20am
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Alaska Boro
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Join Date: Dec 10, 2009
Location: Anchorage, Alaska
Posts: 1,065
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With boro the same issue can be caused by using colors that have a tendency to crack. i.e. NS white is one such color if thick. That solution is to first use boro clear as the base and then build up the color on top. Or mix the NS white with boro.
Have batch annealed beads with very few cracking issues. However, marbles are a different issue!!
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2012-12-20, 2:53am
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Senior Member
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Join Date: Apr 11, 2006
Location: Switzerland
Posts: 575
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With soft glass there is that tendency too. In the Effetre assortment for example the COEs are not all exactly 104 and some combinations of colors are known to be troublesome, like yellow and cobalt. That puts additional tension into the beads. As long as you are batch annealing, I would keep the shapes uniform and try not to mix too many colors in one bead.
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2012-12-20, 3:06am
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Cave Dweller
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Join Date: Mar 29, 2012
Posts: 275
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We bench cool (no blanket, no vermiculite) soft glass all the time with
no cracks and batch anneal at a later date.
The cracking problem is caused by having uneven heat in the glass
as it cools.
(one part of the bead is cooler and contracting faster so it cracks)
Try to make sure there is even heat throughout the bead when it is
removed from the flame, keep spinning it until there is no visible heat
indication, then spin it a bit more because it's still hotter than Hades,
and finally put it into the thermal blanket.
(heat travels upward, rotation helps to give the heat much more even
distribution in the glass as it cools.)
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2012-12-20, 7:28am
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Senior Member
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Join Date: Aug 28, 2005
Location: Sanger, Tx
Posts: 3,552
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Since your basement is cold the fiber blanket will be cold too. Try using vermiculite in a heated crock pot instead.
-Donna
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2012-12-20, 9:44am
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Senior Member
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Join Date: Jul 18, 2007
Posts: 568
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I like the annealing bubbles from ArtCoInc better than vermiculite.
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2012-12-20, 3:44pm
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Junior Member
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Join Date: Oct 15, 2012
Posts: 4
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Thanks to everyone for all their help. We did get some vermiculite for now, but ordered some of the annealing bubbles, too. Malcolm at ArtCoInc was really nice!
I think a lot of this is learning to keep the bead at a consistent temperature after it is finished. My daughter has only been doing lampworking for a couple of months, so she is still getting familiar with these things. She also has only done classes on round beads, so is struggling with the sculpted beads she wants to make. Fortunately, she has a great teacher and after Christmas we'll schedule some time for her to work with her teacher on sculpted beads.
For now, we'll use vermiculite and focus on round, symmetrical beads.
Thanks again for everybody's posts!
Happy Holidays!
Marla
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2012-12-20, 10:44pm
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Senior Member
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Join Date: May 27, 2008
Location: Albion NY
Posts: 517
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Round,barrels,lentel/disk and cones beads are good for basics to build on.
You can try heating the bead evenly and slowly backing it out of the flame untill it's hard, then put it in the bead "hot tub" to soak.
Expect to loose a few as you learn and keep praticeing.
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2012-12-20, 11:00pm
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....uhm...
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Join Date: Sep 24, 2012
Location: Texas
Posts: 1,155
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And practicing dot placement and size and applying stringer can be beneficial to working sculptures. If she wants to do anything with eyes...she needs to be able to place dots well. I personally like sculptures too, but I have to master basics to make my sculptures good. Post some of your daughters beads in the Newbie/Intermediate thread, we'd love to see and we are very supportive. Everyone on this forum is very supportive.
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2012-12-21, 12:17am
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Junior Member
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Join Date: Oct 15, 2012
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Thanks again everyone. Dawn, I'll get her to post a few when she feels confident enough.
You guys have been wonderful!!!
Marla and Amy
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