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is it possible to temper float after it has been formed/cast over a bed of corse chunky sand i.e. quite a heavy texture, annealed nicely. the thickness varies marginally,maybe from 9mm to 11mm max.also is there generally a % of breakages during tempering process as ive heard there is??????
cheers,dan

Dan

Yes you can temper textured float glass. Because you annealed it better than the factory, your chances at success should be better than off the case flat glass. Not every company will work with us so you need to call and ask around. You can not temper any glass with bubbles so fused float glass will not work.

cheers bert,thats what i wanted 2 hear,looks like its gonna be a day on the phones 4 me tomorrow,dan

There is a huge difference from one tempering plant to another. Don't send them a really great piece on your first try with them. I've had nothing but disaster with tempering, but then I don't need too many to blow up before I refuse to try again.

Lynne Chappell wrote:There is a huge difference from one tempering plant to another. Don't send them a really great piece on your first try with them. I've had nothing but disaster with tempering, but then I don't need too many to blow up before I refuse to try again.

Lynne

describe to us your disasters. What kind of glass? What did you do to it first? What kind of tempering facility?

My experience has been a good one. MY first project was 75 pieces. We lost 5 due to a shape issue. A bend on the edge got caught on the rollers and stopped the glass from exiting the heating chamber. Since then I have been more careful about the edges, but more importantly we put glass with a bend on the edge in at a skewed angle so that the bump does not get caught. I have had 100% success since my first try. I have put through large and unusually shaped pieces. The roller furnace that I use has doors that open up 1" so that is my limit for dimensional sculpture. (there is a hydraulic lifter so that they can lift the whole chamber a bit if they want to play. It is a very expensive machine so most companies are reluctant to "play".)

I was told by a glass manufacturer (don't remember who but I found them in the Thomas Register) that my fired and textured glass can't be tempered because the glass has different thicknesses due to the nature of kiln-fired glass. Also that it had to be flat.
Bert, you say your roller furnace opens 1" (inch). Does that mean your sculptural pieces don't vary more than 1 inch in their change of plane?
Also, by the methods you use is it possible to temper slumped serving pieces as long as they don't have bubbles?

Can flat float be slumped after it has been tempered?
jim

Jim Wixon wrote:Can flat float be slumped after it has been tempered?

Yes, but heating it to slumping temperature will cause it to lose the tempering and become ordinary glass again.

I have had a lot of success tempering cast/textured/sandcarved float glass. I've also had a few failures, and some of the tempering facilities I've used have stopped providing the service due to the risk involved, and the inconvenience of having to clean up a shattered piece. All of the broken glass contminates their rollers, and stalls their production. So, in order to stay in good favor, I would play it safe.
Although I have had success with all kinds of irregular shapes and sizes, it is important to leave the edge of the glass fairly consistant. And, in the instance of sand carving, I have been told to carve less than 1/3 of the way through the thickness of the glass-- or 1/4 of the way to be safer.... I applied that "rule" to the depth of the texture of cast float as well-- it is good to limit the variation of thickness to a degree for a better success rate. I would also be hesitant to temper anything thicker than 1", but find out what the company reccomends. And find out their size limitations. Definately run a test piece first! Inspect the float for bubbles-- sometimes they are in there.

Slumping a piece of tempered glass would remove the temper. Tempering a slumped piece might work though, as long as it is within the size/depth limitations.
Good luck!
-elin

lohman wrote:I was told by a glass manufacturer (don't remember who but I found them in the Thomas Register) that my fired and textured glass can't be tempered because the glass has different thicknesses due to the nature of kiln-fired glass. Also that it had to be flat.
Bert, you say your roller furnace opens 1" (inch). Does that mean your sculptural pieces don't vary more than 1 inch in their change of plane?
Also, by the methods you use is it possible to temper slumped serving pieces as long as they don't have bubbles?

In order to temper glass it must have no bubbles. Therefore with a few exceptions it must be float glass. I have not had any problems with my kiln carved float. I believe that kiln carved glass is less likely to break because we have annealed it better than the factory has.

My glass must be less than 1" from bottom to top.

Any glass has to "ride the rollers" if your glass has rolled edges, they must then face up so the glass has an easy ride. The tempering furnace is called a shake and bake as the glass is rolled back and forth inside the heating chamber. 10mm glass takes 5 minutes to heat up to 1100ºF. That is a rate of roughly 12,000ºF per hour. This can be done to a sheet of glass 120" x 60"x 10mm. One company I have worked with will only place the smooth side down on their rollers. Another doesn't care about that. Some won't touch my glass. The trick is to find the right company.

Thanks Bert and Elin, very enlightening comments.
I get many questions as to whether my trays are tempered. Also inquiries about making shower enclosures using kiln-fired glass. Will do some shopping.

The remark about uneven thicknesses at the edges would explain a lot of my problems. Keeping the edge thickness the same would undoubtedly be a benefit. Two of the tempering plants here won't even touch anything with texture, even textured sheet glass. They don't want to have to clean up the mess. And I have frequently had requests for tempered chipped edge glass, but haven't found anyone willing to do it.

Lynne Chappell wrote:The remark about uneven thicknesses at the edges would explain a lot of my problems. Keeping the edge thickness the same would undoubtedly be a benefit. Two of the tempering plants here won't even touch anything with texture, even textured sheet glass. They don't want to have to clean up the mess. And I have frequently had requests for tempered chipped edge glass, but haven't found anyone willing to do it.

I don't see a reason why chipped edge glass won't temper. Have you talked with Oldcastle? I don't know what factory Joel Berman uses but he does send all of his textured glass out to be tempered somewhere in BC

Lynne,
What I found, regarding the edge was that soft undulations weren't really a problem. But, if the edge had a "v" shaped indentation that actually came to a point, or if the edge got very thin, it had a slimmer chance of sucess. So, as far as the chipped edge, it would kind of depend on the nature of the chip shape-- if it is scallopped, and without very crunchy areas, it has a good chance of being fine.

Occasionally pieces I thought were doomed made it fine, and pieces I thought would be fine weren't... So, don't give up yet. The company I was working for at the time was always trying to push the limits, which is exciting. However, as a project manager, it could be VERY frustrating. In the end, it meant that on top of redoing many pieces that didn't make it ($$$), the tempering company we were using (which was only a few blocks from the studio) no longer wanted to risk squeezing these art jobs into their production, which was really an unfortunate outcome. So, I reccommend "safer" designs-- leave a border at the edge, and be modest with the depth and shapes of the texture. And, guage how the tempering co. feels about experimentation-- they may be into it, at which point, you can push the limits, and have fun!

Good luck!
-elin