Embossing float 10 mm glass

[Victoria Balva]

I never worked with float glass before and any related information is highly appreciated. I am working on the project, wall divider 30 by 92 inches, 10 mm thick. I want to create a mix of fiber blanket pattern and dry plaster and then to emboss this pattern into glass. I also want to keep edges of the glass relatively straight and fine detailing of small size texture. What would be the best combination of time hold and comparatively low working temperature? I am thinking of keeping the glass on hold at 1300 -1350 for an hour. Should I go higher for float?

[Bert Weiss]

You need to go hotter. I have 2 approaches that I use, 1420 hold for 40 minutes, or 1480 hold for 6 minutes. The edges get softer on the hotter firing, but I keep the shape intact. That is in my kilns. I can't guarantee it works in yours. I have a friend who fires considerably hotter to get more precise castings on bowls. I'd like to see his work in person. Be sure to put tin side down, or you will get a rough bottom. In my kilns I am able to heat my 10mm at the rate of 600ºF per hour. I use that rate all the way to top temp. I can't guarantee this rate works for anybody. I have never lost a piece using it. I make shower doors.

I use an unconventional anneal schedule for 10mm float. I have used it for decades now. (my controller programs from temp to temp over time)
afap > 1000 hold 1.2 hours
1000 > 900 take 1.2 hours
900 > 700 take .8 hours
700 > 300 take .8 hours

In general, float takes 80ºF more heat to soften and to anneal than the fusing glasses.

[Victoria Balva]

Thank you Bert. Yesterday I run one sample in a small kiln and ,yes, I need go hotter. I'll try 1420 with 40 m hold. Why tin side down? A lot of sources recommend tin up to avoid devitrification. What do you mean that air side down will make it rough? Sorry for questions, but I will run my kiln today to finish peace before Monday and really do not have time to experiment any more

[Bert Weiss]

Thank you Bert. Yesterday I run one sample in a small kiln and ,yes, I need go hotter. I'll try 1420 with 40 m hold. Why tin side down? A lot of sources recommend tin up to avoid devitrification. What do you mean that air side down will make it rough? Sorry for questions, but I will run my kiln today to finish peace before Monday and really do not have time to experiment any more

Try it and see. The big deal with the tin side is where you compress it, it will frost up, as in the inside of a bowl shape. However it only frosts where the surface has been compressed, so it looks really bad.

The biggest deal with float or any glass is getting it really clean. Never ever use Windex. I am a big fan of Glass Plus from the grocery store. It works for me. Learn to detect schmutz on glass.

[Rick Wilton]

Devit with float is much worse with thinner glass. I do not have ANY issue with devit on 6mm or thicker glass. I ALWAYS fire tin side down. Anything thinner is a nightmare, I won't waste my kiln time trying to fire anything thinner than 6 mm.

I am one of those that fires HOT and has little or no holds. In my kilns I've found I like the results of hot and fast firing.

[rosanna gusler]

Thank you Bert. Yesterday I run one sample in a small kiln and ,yes, I need go hotter. I'll try 1420 with 40 m hold. Why tin side down? A lot of sources recommend tin up to avoid devitrification. What do you mean that air side down will make it rough? Sorry for questions, but I will run my kiln today to finish peace before Monday and really do not have time to experiment any more

tin down. The tin acts like a seperator. Air down tends to pick up fiber and grit.

[Victoria Balva]

Thank you. I got devit strips along edges around 1.5 - 2 inches wide. They really do not bother me, but I am thinking to try hand polish ... Is there any sense?

[Bert Weiss]

Thank you. I got devit strips along edges around 1.5 - 2 inches wide. They really do not bother me, but I am thinking to try hand polish ... Is there any sense?

Did you dam the glass? If so, it isn't necessary. As Rick said, I like to work with 10mm glass. I clean it really well, fire tin side down, and have no issues with devit. I never go thinner than 6mm for any reason. The geometry of my glass remains stable, with the exception of the edges which round over, depending on how hot I have fired. With 20mm I will get shape change, but not with 10mm.

[Victoria Balva]

Edges are fine I like them. except devit along the edges. I was thinking to polish it off just a little bit (but really I do not want to spend time on it). Alternatively in my mind the finished peace will have gold leaf applied to some areas and glass may just benefit from combination of gold leaf and mat devit. I think that to go higher temperature and shorter soak could be better in my case. The glass was cleaned perfectly before firing. Now the question is what is perfect cleaning and how could I avoid devit in future on float?

I have another question. There is a low iron glass available. How different it is in firing from regular float?

[rosanna gusler]

The devit was probably from burning out the binders in the fiber paper. To avoid that I vent the kiln up to 1100 f and usually hold there for 20 min or so. This hold just seems to make the glass happier. Venting is huge. R.

[Victoria Balva]

How to organize in the best manner the process of lifting/turning/moving large peaces of glass? Can somebody recommend special vacuum cups for textured glass or any other equipment?

[Rick Wilton]

Looks good Victoria, Rosanna is correct about the devit and venting.

As for low iron, there are many brands (starphire, krystal klear, ultra-white, optiwhite, ultra clear) of low iron and each is slightly different. You likely won't know which you have unless you get it direct from the manufacturer. That being said I usually run a slightly cooler schedule with low iron, I don't think you'd mind the low iron result with the same program however.

Here is a spec sheet for starphire. http://www.jnsglass.com/pdf/Starphire.pdf

[Bert Weiss]

There are soft rubber suction cups I have seen some shops use for textured glass, but not as 3D as in your picture. The cups I have only work on flat glass.

I have a set of glass grips that I use for any shape of glass. I discovered that they are obscenely expensive, and I can't imagine that I spent that much to buy them, but I do have a pair.

I like to use rubber glass handling gloves from CRL. 2 or more people with these gloves can lift and carry glass just fine. I have done this with slabs weighing up to 230 pounds.

I believe low iron glass anneals a bit hotter than regular float, and therefore softens hotter as well. I don't like to use it, so I avoid it unless my client insists on it. I think it will behave reasonably well using the same schedules as regular. Clear glass behaves really odd in the kiln. I have observed that the radiant heat from my elements goes through the glass and heats the sand beneath the glass, before it heats the glass itself. The proof for this comes when I heat 2 layers of 10mm glass on a sandbed with dimples in the sand. The glass over the dimples slumps down in to the dimple and leaves a small bubble between the layers. If the top piece of glass were hotter than the bottom, that wouldn't happen. I have only roof elements.