slumping help please!

[AZ gram]

Another newby question: I tried slumping into an 8" scalloped bowl mold and peeked at the end of the hold at 1250, then added 5 min. four times...so the total hold was 25 min. The result is a nice shallow, scalloped bowl, but it should have slumped deeper...another 1/2"+ or so.

Would you suggest more time, or more heat? or what

[steve_hiskey]

either. It depends on how thick the glass is.

For two sheet thick (1/4in), on a big bowl, I tend to add more time.

for example, I use

300deg/hr up to 1100
100deg/hr up to 1250 hold 10

The slow climb from 1100 to 1250 means that I am usually done before I even get to the 'hold 10'

However, there are other reasons to use different temps. The one I use above is for "bumpy texture on bottom of bowl where you still want the inside to be smooth." If I have a smooth piece on both sides, and I am worried about devit, I might do something like

300deg/hr to 1100
100deg/hr to 1200
500deg/hr to 1300, hold 2hr

The hold 2-3 hr de-cloud-ies the devit spray without climbing to 1400. (a trick I learned on this forum... works great).

have fun.

[Paul Tarlow]

Another newby question: I tried slumping into an 8" scalloped bowl mold and peeked at the end of the hold at 1250, then added 5 min. four times...so the total hold was 25 min. The result is a nice shallow, scalloped bowl, but it should have slumped deeper...another 1/2"+ or so.

Would you suggest more time, or more heat? or what

You could use either (heat or time) -- or a combination of the two.

As a general rule, when I doubt I opt for more time. Things happen more slowly (and often evenly) so you can respond better. For example, a hotter slump is more likely to keep moving during the initial cooling from the top temp.

- Paul

[Tim Swann]

I agree with Paul. I use time rather than temperature on very steep slumping molds. If you get the glass too hot it will slip down the side of the mold too far.

Tim