slumping with irid glass

[chris webb]

Hi, I've just gotten into trying some slumping/draping/drop-outs and was wondering if someone might help me out with a couple of questions.

first I've got a few blanks that have been pre-fired with design elements and I want to slump some in bowl molds and some in a drop out mold. Do I have to do the drop-out mold piece in a different firing or can I fire it in the same batch as the bowl slumps?

Another question, I have an 11" blank that is cranberry glass on the bottom and pink striker on the top with the irid side fired up. Can I slump into the bowl with the irid side slumping into the bowl without messing up the irid?

for the slump firing I was thinking 300 dph 1150 hold 15min
100 dph 1250 hold 30min
50 dph 1350 hold 30 min
checking at 5min intervals

could someone tell me if I am way off here?

thanks you for your time

[Ron Coleman]

Hi, I've just gotten into trying some slumping/draping/drop-outs and was wondering if someone might help me out with a couple of questions.

first I've got a few blanks that have been pre-fired with design elements and I want to slump some in bowl molds and some in a drop out mold. Do I have to do the drop-out mold piece in a different firing or can I fire it in the same batch as the bowl slumps?

Another question, I have an 11" blank that is cranberry glass on the bottom and pink striker on the top with the irid side fired up. Can I slump into the bowl with the irid side slumping into the bowl without messing up the irid?

for the slump firing I was thinking 300 dph 1150 hold 15min
100 dph 1250 hold 30min
50 dph 1350 hold 30 min
checking at 5min intervals

could someone tell me if I am way off here?

thanks you for your time

Best not to fire both pieces at the same time. They both need different temperatures and treatment. The bowl mold will be finished and the dropout ring will just be starting to slump and you will have decide which one to you want to save if you do both at the same time.

For the bowl mold, fire to about 1200 f and watch what happens. With a 12 inch piece you should see slumping start about 1150 and it should take about 20 -30 min to finish, depends on how deep your mold is. The lower temp for the mold will give you less marking on the back too. Irid will slump into a mold without any problems, in fact you can't see any kiln wash marks if you keep temps low. I go about 3 inches with a lot of my irid pieces without any problems.

For the dropout ring you will need more temperature, maybe up to 1300 +. If you haven't done a dropout before, soak at maybe 1275 for a while and see if anything happens, then bump up the heat a little and and wait again. It's much better to take a little longer and get a good piece than to overfire and have one go down the drain. Best to start low and work your way up. Some dropouts may take an hour or so at lower temperatures, but they tend to stay centered on the ring better than using higher temps. Even temperature and well centered glass go a long way to getting a good dropout.

If you're doing irid in the dropout there will be some cracking of the irid because the glass has to stretch and the irid won't. The look isn't all that bad but will be different than slumping into a mold.

Hope this gets you going.

Ron

[chris webb]

Ron, thank you so much for your reply. I will do some fusing tomorrow and fire the drop-out in a different kiln or firing. I can't wait to see how they come out

[chris webb]

Ron, thanks again for your post, I did three bowls the other day, 2 small in my bead kiln and 1 11' fluted in my bigger kiln. They came out pretty well for my first attempt. The big one came out the best though the mold I used had somewhat of a lip and I didn't get one in the slump. It was like I didn't have enough glass, but it looks real pretty with the irid side showing (outside) and sits very level. The 2 small bowls one very shallow (about 1" drop) the other steeper (about 2") both with a lip came out but not as well. The steeper one slumped all the way in but I lost the lip, the shallow one didn't slump all the way so the bottom is a little too round but the lip stayed, this ones lip was 1/2 again as wide as the other. My deductions so far are that the big one should have an initial circle of glass cut a little bigger than the edge of the mold, the small ones could use a little wider circle but I don't know why the steeper one slumped so much and the shallow one so little. They were the same glass, one layer clear thin and one layer pink stricker irid, the shallow one with the irid up the other with the irid clear capped. I'm hoping to do the drop out mold this week.