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I just fused and slumped my first dish, a 5X10" platter. I believe the glass was green aventurine. It was iridized (?) on one side and sparkly on the other. I placed a layer of clear glass on the bottom and put the iridized side face up. I then placed strips of the same glass, iridized side face down so that the sparkly green was showing. It broke in a very neat, straight line right up next to one of the strips. The margins of all of the strips are a little crinkled. I'm guessing I shouldn't have placed the iridized sides together?

Thanks for your input.

Sharon

more info required. what does the crack look like? sharp or rounded edges? schedules used for both firings.

The crack is flat and pretty smooth. Fusing schedule: two hours to 1100 with 15 minute hold, one hour to 1300 with 15 minute hold, then aqap to 1500. Took about half an hour for the layers to join and the edges to round out. Flash vented to 1100. Two hours to 750, 10 minute hold, then turned kiln off. Waited overnight to open. Slumping schedule: three hours to 1100, quickly to 1300, took about 20 minutes to slump. Flash vented to 1050, 10 minute hold, two hours to 750, 10 minute hold. Turned kiln off.

Thanks!
Sharon

flat and smooth doesn't say whether they're sharp or rounded. i'm going to guess that they're smooth and not sharp, which means you thermal shocked it on the way up the 2nd time. this is either too fast ramping the 2nd time, or not good enough annealing on the first time. i'd bet the latter.

your schedules are way off. your annealing is off: not the correct temp for annealing, and way too fast.

your fusing schedule should be something like

400 1150 0
100 1250 0
9999 1500 30
9999 970 15
75 800 0
150 700 0
off

your firing schedul should be something like

300 1100 0
100 1250 30
9999 970 15
75 800 0
150 700 0
off

Sharon,
At what point did it crack. In the fusing, or the slumping? On the way up or the way down? Do you know any of that? It sounds like it happened in the slumping.
Irid to irid of compatable glass will not cuse cracking. The glass will just not stick together since the metals will not bind to each other.

Sorry Charlie. The edges were sharp and Stuart, it cracked during slumping. Charlie, I'm not sure I understand your numbers. Is it 3 hours to 1100 with no hold, etc. (If I remember correctly). Sorry, I'm numerically challenged.

Stuart. The strips were small, less than 1/2 inch. They did fuse together although the edges were a little bit wonky. Is there any way to fix this. I hate to lose my first piece and it is quite nice, except for being in two pieces. Thanks again for your help.

artisand wrote:Sorry Charlie. The edges were sharp and Stuart, it cracked during slumping. Charlie, I'm not sure I understand your numbers. Is it 3 hours to 1100 with no hold, etc. (If I remember correctly). Sorry, I'm numerically challenged.

Stuart. The strips were small, less than 1/2 inch. They did fuse together although the edges were a little bit wonky. Is there any way to fix this. I hate to lose my first piece and it is quite nice, except for being in two pieces. Thanks again for your help.

if the edges are sharp, it cooled too fast the 2nd time.

my schedules read degrees per hour, top temp, hold time. if your controller uses rates, just divide the dph rate into the temp differental to get rates.

example: 400 degrees per hour from room temp to 1150 into a rate is

(1150 - current temp) / 400

artisand wrote:I just fused and slumped my first dish, a 5X10" platter. I believe the glass was green aventurine. It was iridized (?) on one side and sparkly on the other. I placed a layer of clear glass on the bottom and put the iridized side face up. I then placed strips of the same glass, iridized side face down so that the sparkly green was showing. It broke in a very neat, straight line right up next to one of the strips. The margins of all of the strips are a little crinkled. I'm guessing I shouldn't have placed the iridized sides together?

Thanks for your input.

Sharon

irid to irid doesn't fuse well at all. The irrid coating separates the glass and keeps it from fusing to itself. My guess is that if you had 3 layers the coating moved some when you were fusing (because glass wnats to be 1/4 inch thick) and thats why you were able to get them to stick together at all. Normally irid to irid just pops off. (It's the same with dichroic.)

Barbara

Thanks Barbara. I have experienced that with dichroic and should have known it would be the same with iridized. I have had luck with this technique with small pendants, but they were topped with clear glass. What a silly glass to chose for my first big fusing project. Oh well. I'll try again.

Thanks all for your help!

Sharon

Based on what you have described I would say it broke on the way up in the slump, as stated by Charlie. The reason it broke maybe more due to the fact you had varying thickness of glass. I have seen this happen to others as they learn to fuse. The break may actually be a tear in the glass, but I would need to see a photo to confirm my suspicions. A tear can be caused by the added stress seen by the glass on the edge of the discontinuity. The stress is very similar to what is seen from improper annealing. If you have discontinuities you need to slump at a very slow rate going up or you can get tears in the glass.

Tim