Maximizing Kiln Output - Fast Slumps??

[Cindy next door]

I am trying to get a bunch of work done for my opening and should make it with the schedules I use, but it will be close.

In my push in fusing, I have found that I can vent at 300 and open at 150 - even take out and cover with fiber blanket at that temp.

I have a Skutt 1414. My slump cool downs are much slower than fusing cool downs. For a 22" circle a little over 1/4" and 3/8" to 1/2" pieces, I cool down after annealing:

60 degrees to 500
150 degrees to 200


Since I've found I can push the fusing cool down, can I do the same with the slump cool down. Is it really that different?

Cindy next door

[jim simmons]

Since I've found I can push the fusing cool down, can I do the same with the slump cool down. Is it really that different?

Cindy next door

I don't think so. You are coming down from above the annealing range in both cases.

Jim

[Cindy next door]

I've done a second firing adding with large fused inclusions and cool down after annealling

100 degrees to 600 then off.

Then when it gets to 300 I vent and open at 150.

Am I risking anything doing that after a slump? It would seem that a fusing would be more of a problem so I could do it after a slump too.

Cindy next door

[S. Klein]

Cindy: I think that you are pushing it already for a 22" rnd piece. However I think that you can go a bit faster on something 15" or smaller. I'm presuming that you are slumping on stainless or a mold that is less than 1/4" thick. My slumping program for a 22" piece is 30 dph to 860, 60 dph to 600, off. I do (only if necessary) vent at 300, and I have taken pieces out at below 200 with a towel or newspaper over it. Under 15" I go 40 dph to 860, 80 dph to 600 and off.................steve

[Cindy next door]

Okay, just the advice I needed.

The 60 to 600 is great. I do 60 to 500, but it's the 150 to 200 that seems to take forever.

I have to call Skutt because I seem to have a problem going down 30 degrees an hour. I end up either with an error message or it just gets stuck at one temp. Really weird. I use that when "double" annealling for high fires.

Thanks a million and a half for your help.

Cindy next door

[Cindy next door]

Oh, and I forgot about the molds.

The one right now is on one of Brock's big sushi molds. 1/4" steel.

The others will be cylinders, also 1/4" steel - 4" and 6-1/2" diameters. The 6-1/2" is 36" long but will have two pieces on it - one 12" long, the other 18".

Does that change anything with regard to cool down?

Cindy

[S. Klein]

I think that should be fine. You just have to be careful that your mold is cooling as fast as the surface of the piece. Glass wants to be at the same temp throughout...........steve

[Brian and Jenny Blanthorn]

I am trying to get a bunch of work done for my opening and should make it with the schedules I use, but it will be close.

In my push in fusing, I have found that I can vent at 300 and open at 150 - even take out and cover with fiber blanket at that temp.

I have a Skutt 1414. My slump cool downs are much slower than fusing cool downs. For a 22" circle a little over 1/4" and 3/8" to 1/2" pieces, I cool down after annealing:

60 degrees to 500
150 degrees to 200


Since I've found I can push the fusing cool down, can I do the same with the slump cool down. Is it really that different?

Cindy next door

I would suggest geting an ordinary old oven ( 4 cooking )

Now transfer the glass + mould 2 the oven

Get the oven slightly hotter than the glass

Now temp 2 transfer

Well my guess is if ur quick U could probably B at max oven temp

Put glass + mould on rigidized fibre board

Remember its thermal shock U gotta watch out 4 so guard against draughts

MayB put a peice of fiber board over the top of mould

Thin even glass can cool realy fast But U gotta do it evenly

[Bert Weiss]

Cindy

There are no stock answers. It depends on what kind of forces are at work in your glass. I found that I could crack the kiln at just below 500 when firing 7' long x 7"-12" 3/8" thick kiln carved float glass. I never lost a piece. I spent 2 hours or a little more between the first crack and starting the next load.

Colored glasses or varying thickness will present another world of stress problems.

Some people use newspaper or fiberfrax to cover hot glass freshly out of the oven. If you have some pieces that you are willing to risk, you can see just how far you can push the envelope. Of course if the goal is to finish in as little time as possible, risking losing a firing is probably not worth it.

[Cindy next door]

Just stopping at 600 has made a world of difference.

My kiln is at 350 right now and I almost vented, but dared not. It's not a big piece - 12 x 12 - 3/8".

I think about windows out here in Arizona and how much heat they take, so I've been thinking of experiementing.

I haven't taken any out at above 150 - I don't know if it would be too hold to hold the shelf or mold anyhow. But when I do I cover it with fiber blanket.

I ran out to sandblast the last load last night and took the newspaper advice since I didn't have enough fiber blanket to cover both sides and I had to take them off the mold. Thankfully I had no problems.

I may even be able to make an extra firing now.

Thanks for all your help!

[Cindy next door]

Okay, had an idea, maybe a benefit to being in this heat.

I put the thermometer on my outside table. It goes as high as 120. After 15 min., it registered beyond the 120.

Can I take my piece out at 150 and just stick it in the sun?

But, I'm thinking it would end up hotter than 150.

Maybe use a thermometer next to it and shade it to cool down.

Hey, a natural kiln here! ?

[PaulS]

I am trying to get a bunch of work done for my opening and should make it with the schedules I use, but it will be close.

In my push in fusing, I have found that I can vent at 300 and open at 150 - even take out and cover with fiber blanket at that temp.

It's better to cool something very, very slowly that is going to last 2000 years.


Paul