Shard bowl issue

[smallbitz]

In making my shard bowls/plates with tempered glass, I can't seem to get the edges thick enough. I pile the shards up just as thick on the edges (on plate/shallow bowl mold), but for some reason the edges come out like one layer thick and VERY fragile - hardly fused. The middle is perfect. The only solution I can come up with is to dam the piece first, fire and then slump. Just afraid that I'll get a lot of devit with two firings. Any suggestions??

[Stephen Richard]

I suggest trying two separate firings. You have nothing to loose as the current process isn't working. Spray each firing with borax solution. You may have to embrace devitrification is part of the process.

[smallbitz]

Thanks. That's kind of what I figured...I'll give it a try and see if I get better results. Will the borax spray do any good if I'm not firing above 1400?

[Bert Weiss]

Thanks. That's kind of what I figured...I'll give it a try and see if I get better results. Will the borax spray do any good if I'm not firing above 1400?

If you want the glass to stick together, you will have to fire considerably hotter than 1400. You won't need borax on a first firing. Borax will cause more problems than it solves if you get it in contact with the mold. If you need a second firing, the borax will work well for you.

I've been working this process out for a year now. What I learned is firing too cool results in the glass easily falling apart. I have been firing much hotter than I would have imagined.

[smallbitz]

Won't I loose the individual 'shards' look (which is what I'm going for) if I fire that high?

[rosanna gusler]

sometimes you just can not have it all. if it is falling apart/fragile , it needs more heatwork. i would go fast after 1100f to a higher top temp with a short hold. you will just have to do tests. tests tell you more if you do not change more than one thing per test. rosanna

[Bert Weiss]

Won't I loose the individual 'shards' look (which is what I'm going for) if I fire that high?

In my fiber kilns I fire to 1500 and I still get the bubble frit look. Usually I get clarity, but sometimes I get frosty. You have to experiment a lot to surf the wave.

[smallbitz]

Yep, I'm finding that out - can't have it all. I have another test in now adjusting my top temp. Float/tempered glass is new to me, and I haven't had to do this much experimenting in while. I'm actually having a fun/frustrating time with it. Good thing I got the glass for free!! I will not let this go...I'll figure it out, even if it is 'temperamental' (sorry, couldn't help myself ) stuff. Thanks so much for all the advice. This board is such an incredible resource!

[Bert Weiss]

Yep, I'm finding that out - can't have it all. I have another test in now adjusting my top temp. Float/tempered glass is new to me, and I haven't had to do this much experimenting in while. I'm actually having a fun/frustrating time with it. Good thing I got the glass for free!! I will not let this go...I'll figure it out, even if it is 'temperamental' (sorry, couldn't help myself ) stuff. Thanks so much for all the advice. This board is such an incredible resource!

I get my glass for the cost of driving to the tempering factory (about $25). The catch is that it takes quite a bit of processing to break it up in to the frit pieces I want. I started out making castings that seemed to fall apart way too easily so I kept increasing time and temperature until that stopped happening. My next stage produced bowls that were porous, and still a bit weak. Each time I have upped the temperature. Now I am getting solid sheets, but hitting the edge of the devit zone.

[smallbitz]

Success! (After many, many tests ) I had to do it in two firings, but I got the look/thickness/and clarity that I was hoping for! Now for my next question....

I got a lot of tempered glass from a friend (old shower doors) - do I need to keep each piece separated once shattered and use only those shards together? Or can I mix all my shards? Any compatibility issues?

[Bert Weiss]

Success! (After many, many tests ) I had to do it in two firings, but I got the look/thickness/and clarity that I was hoping for! Now for my next question....

I got a lot of tempered glass from a friend (old shower doors) - do I need to keep each piece separated once shattered and use only those shards together? Or can I mix all my shards? Any compatibility issues?

Float glass is a commodity. Most suppliers buy from more than one factory. So, even from the same source 2 glasses of the same thickness that look identical to the naked eye could be totally incompatible. Or compatible. I got a load of broken tempered from my fabricator. They saved pieces that were scratched or otherwise rejected, for me, from a couple of days of production. My fabricator buys a container load of glass every week. They like to mix up their sources so, if one can't supply something they need, another will be able to. That said, they do have their favorites. It turned out that everything I have tested is compatible with Youghiogheny EZ fuse. This means it probably came from the PPG plant in Fort Worth Texas, which is one of their suppliers. I did get a few batches, where they gave me several sheets of the same thickness, and sometimes the same size. Everything I tested turned out to be compatible. I tested the different glasses together, as I broke and processed them, and added a few pieces of the colored glass to the piles. I was really surprised that everything fit together. Previously their favorite source for glass was AFG Montreal (Now named AGC). This factory has closed down. I know that the AGC glasses and the PPG glasses are not compatible, because I have tested them in the past.

[smallbitz]

I have no idea where this tempered glass came from. It could be 5 or 20 years old...guess I shouldn't depend on it being compatible.