Waaaaah! :-(

OK, Let's learn, why did it happen?

I think it's her kiln. Suzi, please pack that kiln up and sit it out by the curb. I'll be by later and haul it away for you.

It's nice to have such caring friends who will go out of their way to protect me. :-)

I think it blew because I didn't wait and let it cool down to ambient room temperature before starting the slump (kiln was still at about 185 degrees when I put the mold and glass in and glass was at about 72 (I had pulled the previous piece that had finished slumping out when it dropped below 200 and put it in the fiber blanket). Sigh.

"Lord, give me patience, and I need it RIGHT NOW!"

:-)

If we say nothing else about Moonraker, let us say he has a heart as big as Wyoming.

Suzi? Cracked on the way up or on the way down? Bet it was on the way up. I used to run pieces as big as 12"x12" up to slump at 450F/hr. I'm talking 1/4" thick here. As my pieces got better (IMHO) that was usually the result of more work going into them. I finally had one crack that had several hours into it. Now I ramp important pieces at 250F/hr. Under

1000F you can't ramp too slow, but you can ramp too fast.

If it cracked on the way down... Too fast or glass locked over rim of mold.

Ah! Impatience. It won't mix well with glass firing.

Another sign from where I used to work:

There's never enough time to do it right, but always enough time to do it over.

Another suggestion. Check your pieces at 950-1000 on the way up. That way if they are cracked you can cool and put them back together and re-fuse them.

If you haven't already done so, you should check out

I used to run pieces as big as 12"x12" up to slump at 450F/hr. I'm

Hmm, wonder what's up here? I bend lamp panel pieces, about 8X 12, trapezoid shape, serpentine curve, etc. daily, or near so, and I fire normally at 1200F/hr, for important stuff of larger size I am down around 450-600F/Hr,(until 750F then hold there for a bit ,15 min,then hit it faster,) depending on other factors. Shelf coverage, thickness variance, etc.

So now I see people here firing at those lower ramps normally and slowing from there more.

Jack, when you do that ,are you talking pieces 1" and thicker?

and Suzi, you KNEW that was going to happen with a thermal shock didn't you? We have all done that, known the earthly properties of something and decided that day they didn't apply to us? I've done/am doing that.

I'm probably over cautious. The pieces I'm talking about are 1/4-3/8 thick generally at least 12" diameter. On a new layup with only 1/8 thick, I go much faster.

Your trapezoids. 1/8?

I'm curious about the 750F soak. Is that above the strain point of the glass you're using? I generally do a 10 min soak at 1000F to let everything stabilize then AFAP if necessary.

One thing to my advantage, or maybe disadvantage, is that I'm not in a hurry. More time than orders. Also my kilns are the only source of heat in the studio.

snipped

To answer, Yes, the traps are for antique/old slag glass lamps, so I bend alot of KOG and Wissmach, but I fuse mostly Bullseye and am playing with some Spectrum again. When I have time, although I did just do a batch of 60 cabinet door and drawer pull handles that came out very nice. Done in Bullseye and Sandberg. Must admit to being pleased with the result.

750 is above the strain point, I believe, and below the annealing point. It has never given me any problem, I just do it 250 F below you, don't think there is a problem either way. Just time , you have plenty and I don't have enough!

You've just discovered how to carry out a thermal shock test, Suzi.

Your piece failed.

Uh, how about just re-fusing this one, then slumping again? (maybe a little slower..) Barbara Dream Master

Autumn is a second spring when every leaf is a flower. ~~ Albert Camus

I don't think re-fusing is an option because of the design.

I made a whole bunch of little "doots" (cut 1/8" cubes of glass and fired to round them) and arranged them in the pattern of a bluebonnet with additional bits-o-glass for stem and leaves on top of a piece of regular thickness clear 3.5"x3.5". Added border of 1/8" green irridescent to edges. Did a full fuse. Placed assemblage on mold and started firing. Piece cracked right through the middle of the bluebonnet.

I'll get a picture of the 5.25"x5.25" version that I successfully slumped earlier up on my webpage and come back and post a link. It's a thing of beauty. :-)

Time to make and fire more doots so that I can start the process again.

Remember, if you catch it on the way up you can often put it back together and only you will know.

Jack

PS Suzi, edges sharp= broke on way down, edges round, broke on way up..... m

Here's the url for the picture (and yes, the picture will be redone as soon as I can find my light diffuser) :-)