Krinkly effect

[Jack Bowman]

I've searched but can't find my problem in the archives.

I am inexperienced at slumping, having done only a couple dozen or so. I've been doing 3/8" thick bowls into a mold and am getting a wrinkled effect at the bend. The surface finish looks like that krinkle spray paint.

Using System 96 and moving from 1175 to 1250 over a period of about 1/2 hour.

Any ideas to prevent the krinkle?

Thank you,

Jack

[Doris Sisk]

Hi Jack -
I am relatively new to this too, but, have you tried not going so hot? When I am slumping a bowl of about 16 inch diameter I only go to about 1160 and hold for about 20 minutes.
I was slumping to about 1220 but had deformities, especially with the large bowl shape.
I, too, use Spectrum 96 glass.

Doris Sisk
http://www.kamehaworks.com

[Lynne Chappell]

I'm not sure if you're describing serious devit, or glass collapsing down the walls. I've had float glass "krinkle" on the top surface from devit - it looks kind of like cracked ice. I've also had krinkly looking glass when I've overfired with iridized glass on the surface. The glass starts to flow down the walls and the irid surface krinkles. Actually in moderate forms, it looks good - gives the irid a more metallic look.

I don't spend that long on my slumps. I take it up to temperature (which changes depending on the width and depth of the opening, from 1220 to 1275) and hold for 10 minutes. Others like to go low and slow. If you're going to slump for 30 minutes, maybe you're firing too hot.