cloudy underside

Val · Post by **Val** » Fri Mar 19, 2004 11:59 pm

Has anybody had a problem with coe 96 clear glass getting a cloudy look after slumping.
I am trying to take a full fused blank that turned out beautifully clear and slumping without getting a cloudy appearance on the underside. No matter how slow or fast I ramp I still have a cloudy appearance to the underside of the glass. Sometimes it looks as if the glass has stretched and sometimes it is just cloudy although it is not devit. Could it be a kiln wash problem? Could it be the ceramic molds I use?

If anybody has any suggestions I'd appreciate some advice.

Val

Bert Weiss · Post by **Bert Weiss** » Sat Mar 20, 2004 1:31 am

Val wrote:Has anybody had a problem with coe 96 clear glass getting a cloudy look after slumping.
I am trying to take a full fused blank that turned out beautifully clear and slumping without getting a cloudy appearance on the underside. No matter how slow or fast I ramp I still have a cloudy appearance to the underside of the glass. Sometimes it looks as if the glass has stretched and sometimes it is just cloudy although it is not devit. Could it be a kiln wash problem? Could it be the ceramic molds I use?

If anybody has any suggestions I'd appreciate some advice.

Val

If you have fired your mold above 1400ÂºF, I would suspect a kiln wash problem. kiln wash needs to be covered up or removed after it has been above 1400. Below that temp it shouldn't be a problem.

Cynthia · Post by **Cynthia** » Sat Mar 20, 2004 2:14 am

Val wrote:... No matter how slow or fast I ramp I still have a cloudy appearance to the underside of the glass. Sometimes it looks as if the glass has stretched and sometimes it is just cloudy...

How slow is slow, and how fast is fast ramp wise? How high are you going temp wise to achieve your bend?

Tim Swann · Post by **Tim Swann** » Sat Mar 20, 2004 11:08 am

Val,

I have had this happen on more than just clear. It shows up on both kiln wash and fiber paper fired pieces. I have found that it is present before slumping, and appears to be a surface devitrification caused during the fusing. I have verified this by using fiber paper on the first fuse, and then flipping the piece upside down and refusing with the same fiber paper. I ended up with the same results as you described on both sides of the glass. Time at temperature does seem to play a part, as does the fuse temperature. I suspect that both the paper and the kiln wash act as a nucleation point to start the devitrification during fusing. The surface can be polished and the effect removed before slumping.

Tim

Tony Serviente · Post by **Tony Serviente** » Sat Mar 20, 2004 5:32 pm

I too have experienced this. I have observed a very specific set of circumstances surrounding it. Project has been fused first, in my case on thin fire. Glass going in is free of visible devit. Project is slumped into stainless with the fused side down. Hazing is confined to only the upper edge. The rest of the project is clear with no marking. If the project is slumped fused side up, no hazing is present. It does not occur on irid. The effect is seen with both Spectrum and Bullseye glass. I have eliminated interaction with the surface of the form, as I see the haze on folds that have not touched the form sides. I made some stabs at a remedy years ago but got nowhere. Anyone figure this one out?

Bert Weiss · Post by **Bert Weiss** » Sat Mar 20, 2004 6:01 pm

Tony Serviente wrote:I too have experienced this. I have observed a very specific set of circumstances surrounding it. Project has been fused first, in my case on thin fire. Glass going in is free of visible devit. Project is slumped into stainless with the fused side down. Hazing is confined to only the upper edge. The rest of the project is clear with no marking. If the project is slumped fused side up, no hazing is present. It does not occur on irid. The effect is seen with both Spectrum and Bullseye glass. I have eliminated interaction with the surface of the form, as I see the haze on folds that have not touched the form sides. I made some stabs at a remedy years ago but got nowhere. Anyone figure this one out?

Tony

I have similar results with clear float, fused and slumped in to a stainless steel, kiln washed mold. Sometimes this can be attributed to tin bloom, but not always. I wonder just how the stainless steel is involved?

Mica is the best resistor I have found for this. It slides down the mold and does not show marks or anything, even with enamels holding it on.

Cold working is the answer most often used to solve it.

Tony Serviente · Post by **Tony Serviente** » Sat Mar 20, 2004 6:07 pm

Yep, knew it wasn't tin bloom since I don't use float, though it looks like it. How do you use the Mica Bert? Previously fused into the glass before slumping? Yes, cold working would do it, but would be cost prohibitive for my situation. I have shifted to glasses that do not show the haze, and used irid down when I can.

Bert Weiss · Post by **Bert Weiss** » Sat Mar 20, 2004 10:20 pm

Tony Serviente wrote:Yep, knew it wasn't tin bloom since I don't use float, though it looks like it. How do you use the Mica Bert? Previously fused into the glass before slumping? Yes, cold working would do it, but would be cost prohibitive for my situation. I have shifted to glasses that do not show the haze, and used irid down when I can.

I'm, still working out the mica techniques. Mica mixed with flux (clear enamel) sticks to float glass. With colored enamels, it can sink in and disappear much like with BE, although if you apply a thick enough coating it stays on top. I have done a few different things like fusing enamel, with an overspray of mica and then slumping mica side down. I have also successfully enameled with a mica overspray and done one firing on a slump mold, with mica down and got great results.

The major trick I have employed is to mix the mica with squeegee oil and thin it with essence or turp or paint thinner and spray that over water based enamel.

I plan to test mica, flux and CMC (klyr fire) [or Ferro spray medium ] on the surface of clear glass. I'm going to test the same in between layers of glass as well.

Val · Post by **Val** » Sun Mar 21, 2004 2:05 pm

I've fused on sttaight on kiln washed shelves and on thinfire paper. Slowest ramp I tried was 250 degrees up to 1000 10 minute soak then 250 up to 1250 soak for 12 minutes. Then down to 950 ASAP and soak 10 mins. The Ceramic molds have not been up above 1300.

I will try a slump with fuse side up and see if this solves the problem.

Val

bskirwin · Post by **bskirwin** » Mon Mar 22, 2004 9:42 pm

Can you sandblast off the cloudy residue and firepolish it again..??? Barbara

Tony Serviente · Post by **Tony Serviente** » Tue Mar 23, 2004 12:16 pm

No, you can't fire polish that way. Temps to bring up a nice glossy surface will also change the shape of what you slumped. Would be nice though.

WarmGlass.com

cloudy underside

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