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Boro Room -- For Boro-related tips, techniques, and questions. |
2016-07-15, 9:47pm
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Member
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Join Date: Jun 03, 2015
Location: Albany, Oregon
Posts: 34
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Large Marbles break in Kiln
I have marbles- large ones 1-1/2 inch and 2 inch progressing along wonderfully, nicely removed punny marks, but in the first hour in the Kiln fall apart. As if super stressed or shocked as if tossed in water. Why?? Perhaps made too fast and all the glass in the marble not consistently heated? Anyone else had this happen? Placed in Kiln at 1050 F. Then within minutes broke clean in half.
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Steve R
Bethlehem Champion, Bravo and Model A PMD2, various hand torches too. Bottled O2 from my days as an industrial production weldor.
Like floral Pendants, Vortex Marbles, and Shot Glasses. Like to make little snails, humming birds and hearts too.
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2016-07-16, 11:42am
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ManBearPig
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Join Date: Jun 28, 2005
Location: Roanoke, VA
Posts: 8,540
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Without seeing it it's hard to say, but could very well be a compatibility issue. Although breaking clean in half is usually a thermal shock issue. How are you finishing them? With hot fingers or in a marble mold? The only times I've had an issue like this are when I finish them in a mold. The graphite sucks heat out and can cause thermal shock. A lot of people do it successfully all the time. But the only times I've done it I've had experiences like yours.
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2016-07-16, 11:57am
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Member
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Join Date: Jun 03, 2015
Location: Albany, Oregon
Posts: 34
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Thanks Cosmo--- They do look like thermo shock. Using graphite mold-- the same one I round the Marble-- so it is hot- but still it is a pretty massive piece of graphite. Also I use my Little Smith torch with a number seven tip to mend the puny scar--- so maybe too much heat in one spot.
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Steve R
Bethlehem Champion, Bravo and Model A PMD2, various hand torches too. Bottled O2 from my days as an industrial production weldor.
Like floral Pendants, Vortex Marbles, and Shot Glasses. Like to make little snails, humming birds and hearts too.
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2016-07-17, 9:36am
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Senior Member
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Join Date: Aug 27, 2005
Location: Florida
Posts: 2,186
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Questionable DICHROIC Glass???? is the title?? Are the breaks along the dichroic glass? It the marbles are breaking at the juncture of the dichroic and the boro then maybe someone sold you Bullseye or 104 dicro?
You also may be allowing the marbles to cool too much before taking the punty marks off with the small smith torch.... Why not use your regular torch with the flame turned down? Aim your torch the direction you need to get the mark off just before you put it in the kiln. There are lots of inexpensive tools for moving hot marbles to the kiln and allow you to remove the punty marks without having to change torches.
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2016-07-20, 8:12am
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ManBearPig
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Join Date: Jun 28, 2005
Location: Roanoke, VA
Posts: 8,540
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If you bought some of that cheap dichroic glass off of ebay, that could be the issue as well. Some of that is made from old spotlight projector lenses and has a plastic coating on it.
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