What went wrong? - WarmGlass.com

What went wrong?

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KatyPattison
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What went wrong?

Postby KatyPattison » Mon Sep 29, 2003 10:42 am

Hi, I taught a class this weekend and I have no clue as to what went wrong. I have been making dichroic glass jewelry for over 6 years (I have 80 + wholesale accounts) and have never had this happen before. I have also taught this class, using this kiln, about 3 times and using a different kiln twice.

All the glass I was using was Bullseye or Uro 90 (some of my dichro is coated on Uro). We used a coe 90 black irid, a clear, some cobalt blue as our bases and the clear caps. We were using dichroic pieces that have been fired before with a clear cap (by me so I know the glass was all COE90) and unfired dichro (again all was from my own supply so I know it was COE 90). Some of the dichro was Austin Thin but the majority was CBS. Every piece has been used by be in my jewelry. It has never cracked or divitried.

I fire using this schedule, in my kiln, with these glass combinations at least once a week and never a problem!

First the results:

About half of approximately 60 pieces, randomly positioned in the kiln were very cracked and divitrified. They were not pieces made only by one person. They were not grouped together. They were not all the same base glass. They were not all using prefired pieces. They were not all using unfired pieces. They were not all using a combination...... I think you get the picture, there were no common factors. It was so bizarre!

Here is the schedule, it has alway worked before. Keep in mind the largest pieces are not more that 2" by 3". I cut the base glass and the clear glass into 1 1/2" - 2" by 3" strips for each student to use, they can cut those smaller if they want or use them that size. The pieces may have many layers ie. base glass, piled dichro shards, clear cap.


500 degrees per hour to 1000
AFAP to 1400
300 dph to 1500 soak time entered 15

(I shut it off as soon as the majority have been cooked to satisfaction, in this class we try to have them quite well rounded because a lot of the students don't have kilns and want nice rounded cabs at the end)


Since I am teaching and the majority of the students don't have fusing experience we do look into the kiln at various temperatures. I do this every time I teach and so it is not something new. (learned it from Bob Leatherbarrow so how could it be wrong!) I crack the kiln about an inch for about 20 - 30 seconds. We look in at about 1100 to see if it is starting to slump, again at about 1300 - 1350 to see the edges getting shiny and again after a few minutes of the soak at 1500. I then shut the kiln off and go home, nobody touches in until the next morning, no opening and thermal shocking. The only shocking was mine when we opened it Sunday morning!

Does anyone have any word of wisdom for me, I hate teaching when you have to say "I absolutley have no clue what happened!" Makes you humble!

Katy

Bob
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Postby Bob » Mon Sep 29, 2003 10:51 am

Hi Katy,

Was the problem with the Large Fusion Stained Glass kiln? When I taught last weekend I noticed the devit problem. I had not cracked the kiln open to vent during the initial heating phase. I had guessed the problem might be the binders were not completely burned off... but that was a guess.

The cracking problem is a total puzzle. Was the cracking through the glass or just as surface crazing?

I think you must have upset the kiln goddess hanging on the wall above the kilns.

KatyPattison
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Postby KatyPattison » Mon Sep 29, 2003 12:54 pm

Hi Bob, it was the big kiln, however, I have used that kiln many times this summer (probably 15 firings) for my production work and nothing.

Not all the pieces had divit only the pieces that cracked. The cracked pieces were not just crazed, they were more of a shattered crack. Some just the clear, you could almost separate the shattered/cracked clear off of the rest of the piece. Some were cracked all the way through to the base glass. I left one on the shelf in the back so if you are in there have a peek.

You are probably right about the goddess, this is my first class since May and probably the only one that I have not pointed her out.

Let it be known that the Fusion Kiln Goddess doesn't like to be ignored!

Katy

Marge B
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Postby Marge B » Mon Sep 29, 2003 3:01 pm

Just a thought - may not mean anything - but how about dicro surface to dicro surface? was that a factor? :?

I just hate it when the kiln gods make us look bad, like we don'thave enough to wory about.

Marge

KatyPattison
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Postby KatyPattison » Mon Sep 29, 2003 3:27 pm

Thanks for the response but that isn't a factor. I would say that it was thermal shock if all of the pieces had been affected or if just the ones in one spot had been cracked but they were evenly spaced throughout the kiln on two shelves both 20" square. They broke like a high temp melt that just shatters. I am baffled, must be that Goddess! and boy did she make me look bad!

Jackie Beckman
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Postby Jackie Beckman » Mon Sep 29, 2003 7:52 pm

Could it be that the kiln wash had broken down in the area where the cracking took place? That would cause the glass to stick to the shelf and shatter.

KatyPattison
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Postby KatyPattison » Mon Sep 29, 2003 9:33 pm

I don't think that was the case, both were freshly cleaned and washed. Good idea though!

Ron Coleman
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Postby Ron Coleman » Mon Sep 29, 2003 11:05 pm

If only the cracked pieces had devit (on the clear?) I would be suspicious there was some incompatible glass mixed in. Possibly even a non fusible glass. Of all the fusible glass that devits, clear isn't one of them in my experience.

Ron

Ron Coleman
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Postby Ron Coleman » Mon Sep 29, 2003 11:15 pm

Just thought of a test you might run if you still have some of the cracked pieces. Cap them again with known good BE or URO 90 clear glass and fire again. Look for cracking in the finished pieces.

Ron

KatyPattison
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Postby KatyPattison » Mon Sep 29, 2003 11:34 pm

The only clear bullseye glass I have ever had in my studio has been coe 90. I have a very small amount of spectrum 96 but it is the very smooth surfaced glass and all of my bullseye clear is the slightly textured glass. All of the dichroic glass is coe 90. It all has been used in my pieces and all is from full sheets that I have had coated for me. All of the fused, capped pieces that we used were the "skeleton" left over from when I water jet cut some of my pieces. I have used everyone of those in the cabochans that I make. I know they are both fusible and coe 90. I also used a black irid, a light blue and a cobalt blue that still had the orange bullseye sticker on them. This is why it is all so confusing.

I will certainly try your idea of refusing, a couple of the people in the class are always around Fusion and will certainly give them back to me, I also kept one to show to Bob and see what he thinks.

Thanks for you help, this may be one of those "we will never figure it out things". I am going out of town on Thursday but I would like to go into Fusion next week and run the exact same schedule with the glass that I still have in my teaching box and see what happens.

Katy

Melissa Terman
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Postby Melissa Terman » Tue Sep 30, 2003 9:49 am

I was talking to another fusing artist recently and he was telling me of some glass he received from BE that was incompatible. I'm not remembering the color for sure, but I think he was talking about crystal clear. He showed me through the polariscope the stress in his piece (which he was preparing for SOFA/Chicago). He makes large-square platter shaped pieces as wall art. I think he had 4 pieces with stress all in this one concentrated area. And, he knew it was the glass he received from BE because he ran out and ordered some more and used it in the same area on each piece where stress occurred.

The moral of the story is, Don't believe everything you read. Sweet little orange stickers can lie.

One other thing you can check. Was there a full moon on the day of the firing? :)
Melissa Terman

KatyPattison
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Postby KatyPattison » Tue Sep 30, 2003 10:00 am

That is the only thing that makes sense, all of the clear is glass from sheets I have used but I cut 8"x8" pieces out to fuse over my dichro. The strips of the edges are what I use in the classes. Non of the 8x8s have ever behaved strange but maybe there was an area of incompatible glass along the edges of one sheet and we were just unlucky enough to use it in the class.

Everyone on this board is so creative both with their hands and their ideas! Many minds definitely come up with many different ideas, thanks to everyone

Katy


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