Jan, my comments are in a

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Stephen Richard

Jan, my comments are in a different colour spread throughout your post. Oh preview shows there is no different colour.

“Stephen, Thanks so much for all the info. I bought fibre paper and tried another project which turned out fine. It was about the same size and covered 3/4+ with a second layer. My schedule was as follows:  275dph to 1000 hold 20 min,   100dph to 1350 hold 20 min, 9999 to 960 hold 1 hr. I slowed way down the speed going to 1350.  I want to try the John Deere emblem again. I read that two pieces of glass the same size have trouble getting the air out, but you can prop up the second layer with a small piece of glass and it disappears when fused.”

I have fused two sheets of glass up to 800 by 500 mm and had no difficulty in the air getting out from between layers.  The small pieces of glass will not completely dissapear.  They will have the appearance of little bubbles.

“Or I could try just the one layer again but without the border.”

Yes that would make it easier on the single layer.

“I could skip the border on  the double layer also.”

You don’t need to, if you have a bubble squeeze.  I emphasise that is not at 1000F ( a temperature above which the glass will not be temperature shocked – called the strain point).  Even S96 state that is at 1150F.  That is the temperature you need to soak at.

“I have the schedule suggested by System96 which has 6 segments. I can use that but they recommend 200dph to 1350 and I could slow that down to 100dph because that worked in the other project.”

Unless you know why it worked on one project and not another, you don’t have a good basis for decision.  Once you are past the bubble squeeze, it does not matter much how quickly you go (with certain limitations).  Review this document


and you will see that going slow in this region is going to give a problem of devitrification.

“I also read that a bubble squeeze could be held as long as 2-3 hrs for projects that pose problems. So I believe that means I could hold at 1000 for a much longer time.”

Again, 1000F is not a bubble squeeze, it is the strain point.  The bubble squeeze is at 1150F.  The long soaks are for very complicated and multilayered pieces.  30 mins should be sufficient.   A soak at too low a temperature does not do anything as the glass cannot fully slump, so when you speed up and go to higher temperatures, the piece seals the air that is left within.  Make sure your bubble squeeze is at a high enough temperature.  Look again at the S96 site and you will see 1150 as the temperature.

“Please tell me what you suggest and again thanks for sharing your knowledge and time. Jan”

Best wishes

Stephen Richard

blogs at: http://www.verrier-glass.blogspot.com/ and  http://www.glasstips.blogspot.com/

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