What temp can you take your fused glass out of kiln?

deborahbur · Post by **deborahbur** » Thu Apr 10, 2003 6:29 pm

How soon can I take my fused or slumped glass out of the kiln? What should the temp be to be safe?

charlie · Post by **charlie** » Thu Apr 10, 2003 6:36 pm

deborahbur wrote:How soon can I take my fused or slumped glass out of the kiln? What should the temp be to be safe?

if i don't have to, i let it sit until room temp. if i have to, i open the kiln at 200, and take it out and wrap it in towels at 150.

of course, in the summer, room temp is 115-120.

Brock · Post by **Brock** » Thu Apr 10, 2003 6:50 pm

Whjat size culleet do you want to make? Brock

Geri Comstock · Post by **Geri Comstock** » Thu Apr 10, 2003 7:35 pm

The best idea is to let it cool to room temp before removing it.

In a pinch, I've wrapped it in several layers of heavy duty towels at about 115 and it was fine.

Once when I first started fusing I took a piece out when it was too hot. That night about 3AM, it exploded into hudreds of little pieces. Scared the crap out of me, waking me from a sound sleep. LOL.

Good luck!

Geri

Colin & Helen · Post by **Colin & Helen** » Thu Apr 10, 2003 7:59 pm

For glass about 40c ...I find my kiln will take several days to cool to room temperature...

Just a side note on removing work while still hot... When I was working in pottery/ceramics I would use a white glossy glaze that woud craze ...pots would be fired in the normal way then at 400c removed from the kiln using tongs the sudden drop in temperature will cause the glaze to crackle .. the pots are then put back in the kiln and let cool then at 100c they would be removed again and the surface would be wiped over with red indian ink ....this would colour the cracks and give a slight tone to the glaze.....I have often thought if only this could be done in glass?????? Colin

Marty · Post by **Marty** » Thu Apr 10, 2003 9:14 pm

If you need to, start cracking the kiln at 250 to 300F. Start with a 1/4" gap at 300, 1/2" at 250, 3/4" at 200, 1 1/2" at 150. and 3" at 125. It'll come to room temp in no time.

The above not only speeds things up, but it also makes you feel like you're actually involved in the process. Don't stand around watching the pyrometer- start on new stuff!

gone · Post by **gone** » Thu Apr 10, 2003 10:10 pm

[quote="

Once when I first started fusing I took a piece out when it was too hot. That night about 3AM, it exploded into hudreds of little pieces. Scared the crap out of me, waking me from a sound sleep. LOL.

quote]

I didn't think you could get delayed breaking like that from cooling too fast. I thought that thermal shock happens while the piece is being subjected to uneven heating or cooling, not hours later. If you got it cooled in one piece and it's annealed correctly, the speed at which you cooled it won't matter, right???

Els

Kevin Midgley · Post by **Kevin Midgley** » Thu Apr 10, 2003 10:38 pm

The Boyce of book fame has said you can never over anneal. The slow cooling to room temperature and when you can get the glass out of the kiln without burning your hands is telling you the difference, the IMPORTANT difference between the internal temperature of your glass and the air temperature your thermocouple is reading. Pay attention to that and you can make pieces that stay together. I have regularly opened a kiln to crash cool single layer slumped 5mm float at 700 F. but you had better have annealed it properly if you want to try it. A 200 F temperature on a thermocouple is the absolute crazy max I have bare-handed-hot- potatoed a glass piece into blankets. OUCH! I prefer under 100 F. The 200 is definitely not recommended.
Kevin

watershed · Post by **watershed** » Thu Apr 10, 2003 11:15 pm

And for those casters out there. I have found the 350-100 degF range to be critical.

Here's my example. I open the oven at 350, look at the open faced molds. They look fine, no cracks. If I leave it cracked to say 100degF, then look, and they have cracked.

That's all I know.

greg

Geri Comstock · Post by **Geri Comstock** » Fri Apr 11, 2003 1:00 am

Els VandenEnde wrote:[quote="

Once when I first started fusing I took a piece out when it was too hot. That night about 3AM, it exploded into hudreds of little pieces. Scared the crap out of me, waking me from a sound sleep. LOL.

quote]

I didn't think you could get delayed breaking like that from cooling too fast. I thought that thermal shock happens while the piece is being subjected to uneven heating or cooling, not hours later. If you got it cooled in one piece and it's annealed correctly, the speed at which you cooled it won't matter, right???

Els

I didn't quite explain this right...when I took it out of the kiln too hot, I heard that noise of glass stressing from thermal shock that we all know too well...it didn't break immediately, though.

It was a delayed thermal shock break just like that glass table I mentioned not long ago that exploded from thermal shock hours later.

Yes, glass can break from thermal shock hours later. It stresses from thermal shock, but it can take a while for it to actually break from the stress (or explode in these two cases).

Best -

Geri

gone · Post by **gone** » Fri Apr 11, 2003 1:42 am

[

Yes, glass can break from thermal shock hours later. It stresses from thermal shock, but it can take a while for it to actually break from the stress (or explode in these two cases).

Best -

Geri

Hi Geri,

That was actually what I was questioning. I didn't think glass could retain stress unless it was introduced at annealing. Maybe the delay in breaking, in your case, was that it was still cooling hours later. Was it thick? Or am I wrong about the residual stress thing?

Els

Bert Weiss · Post by **Bert Weiss** » Fri Apr 11, 2003 2:33 am

Kevin Midgley wrote:The Boyce of book fame has said you can never over anneal. The slow cooling to room temperature and when you can get the glass out of the kiln without burning your hands is telling you the difference, the IMPORTANT difference between the internal temperature of your glass and the air temperature your thermocouple is reading. Pay attention to that and you can make pieces that stay together. I have regularly opened a kiln to crash cool single layer slumped 5mm float at 700 F. but you had better have annealed it properly if you want to try it. A 200 F temperature on a thermocouple is the absolute crazy max I have bare-handed-hot- potatoed a glass piece into blankets. OUCH! I prefer under 100 F. The 200 is definitely not recommended.
Kevin

I work with heavy float glass and my rule is wait until you can handle it with bare hands. 180 is cool enough for me to open the kiln and a few minutes later I can remove it. Only once did a table top break in 2 in my hands. Colored glasses are much less forgiving.

Gale aka artistefem · Post by **Gale aka artistefem** » Fri Apr 11, 2003 8:54 am

Now I know better than to do this!!

But - here I was last weekend running loops around myself working a show. Took a look in the kiln Sunday morning after a late Saturday night firing and the amount of heat coming out of the kiln "seemed" negliable. So I reached in, pulled out that pretty oval platter (was bit on the "warm" side, but I could still handle it with bare hands), wrapped it up, put it in the car with me and took off for day number two of the show.

As I'm pulling into the parking lot of the show, I hear the unmistakable 'PING" of a thermal shocked piece of glass.

I now have three pieces of a pretty oval glass platter.

......and when I got back to the studio later that evening , I found laying on my bench the platter mold neatly broken right down the center in two equal halves. Big double ARGH!!!!!!!!

Guess I'll now be making pretty oval platter "halves" now for the diet conscious - LOL!.

If the glass seems a bit on the warm side - DON"T TAkE IT OUT!

.......and I knew better than to do this

Patience and more patience is the key.

Jerry · Post by **Jerry** » Fri Apr 11, 2003 11:28 am

Dan Fenton, bless his little trouble making heart, when asked the question about when it was safe to take something out of the kiln said; "When you can lay it on your belley, it's safe to take it out."

Dan can say things in ways we can all understand.

Jerry

Geri Comstock · Post by **Geri Comstock** » Fri Apr 11, 2003 11:53 am

Els VandenEnde wrote:[

Hi Geri,

That was actually what I was questioning. I didn't think glass could retain stress unless it was introduced at annealing. Maybe the delay in breaking, in your case, was that it was still cooling hours later. Was it thick? Or am I wrong about the residual stress thing?

Els

Both of the pieces I'm referring to were thick float glass. They both made that "ping" breaking noise from thermal shock, one when subjected to uneven heat (a commercially made, thick float glass table top), the other when subjected to rapid cooling while it was still very hot (probably 200F or more), and it took them a while to finish breaking. I suspect it's because both were quite thick.

I'm not sure what you're asking, but yes, they did both break from thermal shock in my opinion. It started immediately (the "ping" noise in both cases when heat and cool were applied), but took a while because they were thick.

Geri

Patty Gray · Post by **Patty Gray** » Fri Apr 11, 2003 12:01 pm

When working with thicker pieces even venting a little can cause it to break (I have experienced this and it is a bummer). Experimenting is the best way to find out for your processes.

charlie · Post by **charlie** » Fri Apr 11, 2003 12:26 pm

Geri Comstock wrote:Both of the pieces I'm referring to were thick float glass. They both made that "ping" breaking noise from thermal shock, one when subjected to uneven heat (a commercially made, thick float glass table top), the other when subjected to rapid cooling while it was still very hot (probably 200F or more), and it took them a while to finish breaking. I suspect it's because both were quite thick.

I'm not sure what you're asking, but yes, they did both break from thermal shock in my opinion. It started immediately (the "ping" noise in both cases when heat and cool were applied), but took a while because they were thick.

Geri

isn't long term cracking a sign of tempered glass? when i broke a tempered car window, it continued to crack for days.

perhaps it wasn't annealed well enough and actually got tempered somewhat.

WarmGlass.com

What temp can you take your fused glass out of kiln?

What temp can you take your fused glass out of kiln?

Re: What temp can you take your fused glass out of kiln?

impatience

Temp?