White Ware

BMaxham · Post by **BMaxham** » Mon Dec 22, 2003 1:02 am

A family member, thinking they were doing a good thing, bought me two molds for slumping, however they got them from a ceramics store. They are labeled as "White Ware from Laguna Clay. Can I use these for glass? They are both marked on the bottom not to fire at a ramp rate greater than 250 C per hour, much less than the typical rate I use. I have tried some of the ceramics forums, but no answers there.

Thanks for any help.

Tony Smith · Post by **Tony Smith** » Mon Dec 22, 2003 7:33 am

What are you slumping that you can ramp up at more than 480Â°F per hour?

Tony

rosanna gusler · Post by **rosanna gusler** » Mon Dec 22, 2003 8:03 am

i think that they mean not to go fast through quartz inversion temps. we are generally going full on at around 1150f. darn i wish i could remember the exact number. anyhow i have broken molds going fast there. rosanna.......ok i looked it up, quartz inversion happens at 573c or 1064f. i go slowly through those temps as a favor to my kiln brick and furniture. i hold at 1150f or so for evinivity, then blast off. google quartz inversion sometime. it is a good read.

Ron Coleman · Post by **Ron Coleman** » Mon Dec 22, 2003 8:48 am

I think the point of confusion about the firing rate is degrees F and degrees C.

250 "C" is more than fast enough for any slumping .

Ron

BMaxham · Post by **BMaxham** » Mon Dec 22, 2003 9:25 pm

Sorry, I meant 250 F, not C. I typically ramp at ~400 F/hr, hold for a few minutes and then up AFAP to ~1300.

Geri Comstock · Post by **Geri Comstock** » Mon Dec 22, 2003 10:02 pm

I don't know what you're slumping, but that sounds awfully fast to me. I'm really surprised you haven't had breakage.

What kind of glass are you using and what are you slumping (how big, how thick, etc.)?

250F is the rate at which I generally slump.

Geri

BMaxham · Post by **BMaxham** » Mon Dec 22, 2003 11:32 pm

I've slumped a variety of types of glass; Bullseye, Spectrum (standard and System 96), & Gecko, 2 inches to 22 inches in diameter and as many as three layers. So far have never had any breakage.

I use profiles suggested by Spectrum as the starting point for all of my work. For System 96, a piece 12 inches and 2-3 layers they recommend a ramp rate of 400 F per hour. Even for larger pieces, where I would ramp in three stages, the slowest rate is 400 F per hour.

Jim Wixon · Post by **Jim Wixon** » Tue Dec 23, 2003 12:01 am

250Âº Æ’ is my slump rate...you may need to drill holes(or not)...kiln wash...and go for it