My glass refuses to slump further

[Sadna]

I need advise on a piece I am working on. I am trying to slump a square two layered piece on metal tray which is a sectional tray. I have tried slumping this plate 4 times already, but it refuses to slump in the trench part of the metal tray. I even drilled air holes in the metal tray and suspended it on kiln posts to ensure proper air circulation.

The last temperature I went up to was 1320 for 5 minutes. I have read Bullseye’s tech tips on heat and glass, but this piece’s refusal to slump makes no sense to me.

My questions are:
How high can I go to safely slump the peace without making it all melted.
And is it safe to slump the fifth time?
Does making hold time longer at 1320 help? For how long?

[Mary Kay Nitchie]

Hi Sadna,

Some questions:

What style numbers of glass are you using in this piece?
What are the dimensions of the whole mold?
What are the dimensions of one section of your tray?

Looking forward to learning more about your project.

Mary Kay Nitchie
Bullseye Glass Co.

[Monika]

Sadna,
can you post your complete slumping schedule?
and to add to Mary Kay's questions
How deep is you mold/tray/section you want to slump into?

just a note up front - a 5 minute hold want do much,
lower temp and a longer hold (maybe hours) might give you a better result.

[Sadna]

Hi Mary Kay & Monika,
Thanks for your replies.
The glass I am using are, one layer of Clear & white streaky-2130, and second layer is a mix of canary yellow-1120 & Orange - 1125.
The mold is not more than 3/4" deep.
Size of the mold is 12"X12".
Some sections are: 5"X5", some are 4"X4".
Slumping schedule I am using is from Skutt folks and I have used that schedule for all my pieces and so far results have been good.
Here it is:

Step 1 2 3 4 5 6 7 8
Rate 300 300 300 600 600 9999 30 60
Temp 250 500 750 1150 1320 1000 970 750
Hold time :25 :25 :25 :05 :05 2:00 2:00 :01

Thanks you so much for you help, it is really appreciated.
Sadna

[Mary Kay Nitchie]

Hi Sadna,

It can take extra time and practice to slump glass across a section's short span (2-5 inches across), especially if the sides are canted steeply. I think holding at process temperature for 10 minutes and then checking it every five or ten minutes would help you find the right cycle. Keep notes as you are keeping time. That way, when you DO find out how much time the slump will take under these circumstances (this particular mold in this particular kiln with this particular glass at this particular process temperature) you can program this slumping cycle in the future. In the future, even when you have the new successful cycle programmed, we recommend peeking at your project at the process soak temperature to make sure the piece slumped according to your expectations before continuing with the rest of the cycle.

Whether or not it will need to be at process temperature for an hour, I can't confirm.

Mary Kay

[Monika]

Sadna,

Not quite sure if this will help you but I did a slump into an 1.5 x 1.5 x 1 inch opening and it took a loooong time to slump. (this took about 18 hours to finish)

this is one - others had 6 openings to slump

flower-bridge-empty.png (8.77 KiB) Viewed 629 times

If I would be you I would read all the BE technotes available and than change my schedule- I would use maybe 4 steps
1 - slow to 1150 and for an hour or so but check in between if the glass had moved - if not or not enough you could extend time or go
2 - 100 to 1250 and hold for as long as it takes (add time and not heat to avoid distortions)
3 - 350 to 900 hold for anneal
4 - low to 700 check BE technotes and off to room temp.
again (I don't want to sound too preachy but) read BE technotes and firing schedules - take very good notes - and develop your own schedules for your projects - you'll have more success and less disappointments.
Put it back into your kiln - Good luck and lots of patience for your attempted slump.


(Tip: I set my kiln on delayed start - so that it will be at 1150 in the morning when I had time to check on and off during the day)

[Sadna]

Monika & Mary Kay,

My piece slumped, finally!!! It took two hours at process temperature.

Thank you so much,
Sadna

[Mary Kay Nitchie]

Sadna,

Glad to hear that you found the solution! Plus, I learned vicariously from your experience, and I am sure others did, too. Thanks to you and Monika for contributing!

Mary Kay