Page 1 of 1

Why want it slump?

Posted: Sat Apr 12, 2003 4:35 pm
by Betty
I put one piece of glass, not the heat glass just regural glass, in the kiln and it didn't slump in the mold. Won't regural glass slump or does it need to be hotter to slump. there are just so many beautiful glass it seems a shame not to try a few.

Posted: Sat Apr 12, 2003 5:02 pm
by Tony Smith
Do you mean window glass (float glass) when you refer to "regular glass"? If so, you will find that it slumps at higher temperatures than art glass. Keep raising the temperature until it starts to move, then hold until it's fully settled in the mold.

Tony

Art Glass

Posted: Sat Apr 12, 2003 8:33 pm
by Betty
What i am using in the stained art glass. I just want to slump it in some small molds.

Posted: Sat Apr 12, 2003 8:36 pm
by Brad Walker
And what temperature are you firing to?

Posted: Sat Apr 12, 2003 8:53 pm
by Betty
It is a new kiln, skutt Hot start, and I am using the preprogramed settings. The insturation are confusing for me.

The firing was medium speed and slump with a soak of 1225 for 15 minutes

Just what all this means i am still learning.

Posted: Sat Apr 12, 2003 9:00 pm
by Betty
Rate Soak Hold
400f/hour 600f 5 min
600f/hour by process by process
9999f/hour 960f 40 min
175f/hour 800f 10 min

like i said it still makes no sence to me but it willl

Posted: Sat Apr 12, 2003 11:00 pm
by Brad Walker
Actually, it's a strange firing schedule and I'm not sure I understand the logic behind it either. Nevertheless, if a soak of 15 minutes at 1225 didn't work, then I would soak for longer at that temperature.

In general, you need to know the type of glass, the thickness and size of the glass, and the type of mold in order to select a proper firing schedule. The type of mold is especially critical, because different molds require different amounts of heat to slump properly. Small molds generally take longer soaks or higher temperatures (or both!) than big ones.

In general art glass will slump between 1100 and 1300 F, after a soak of 0 to even 60 minutes or more. It all depends on the factors I mentioned in the previous paragraph. But the critical thing to know about slumping is that if you're inexperienced with the particular slump you're trying you need to watch the glass carefully to learn how it will behave. And don't be afraid to slump for a longer period of time if necessary.

Posted: Sat Apr 12, 2003 11:51 pm
by Lynne Chappell
If the stained glass is Spectrum, then it should slump at 1225 if the mold is a decent size. If it is Kokomo, Wissmach, Armstrong, then you might have to go higher. Some of them devitrify (get scummy on the surface) even at those low temperatures and then they don't slump well.

I have found that some factory programs don't go hot enough for small molds (or get there too quickly for the heat to do it's work). Change the process temperature to 1275 and see if that does the trick. I can't tell you exactly how to do that as I haven't used that particular controller, but I think you hit the up arrows and it goes up 10 degrees at a time, or something like that. The manual should tell you how.

Posted: Sun Apr 13, 2003 10:47 am
by Betty
I would love to change the temp. but the direction are confussing to me. Going away for a week and will call Skutt when i get home.