Compatibility Shift

[Yardic Glassworks]

I was recently working on a piece about an inch thick and 17 by 17 inches in size. The glass used was Bullseye opaque white (sheet and stringers), 0013, along with light neo-lavender shift and crystal clear. On the third firing I experienced a dramatic shift in compatibility by the opaque white. The piece fractured along just about every white line, and within a number of squares surrounded by the white. None of the firiings were above a standard full fuse temp. I am aware that people have experienced compatibility shifts with Bullseye's dense white. Anyone have a similar problem with the opaque white? Tim

[Marty]

Tim- Please post your schedules.

[Yardic Glassworks]

The initial firing schedule prior to cutting with the tile saw was as follows:
150-350-90
100-1100-120
100-1250-60
300-1510-90
9999-1100-60
70-900-330
60-830-60
60-760-210
80-350-0

The second fusing schedule was as follows:
80-350-90
60-11-12-
100-1250-60
300-1490-60
9999-1100-60
70-900-330
50-830-60
60-760-210
80-350-0

Black markings on the attached photo show the patterns of the cracks.

[Marty]

Tim- the only thing that stands out is the long hold at 1510. Are you sure that's necessary? Have you tried longer/lower?

[Yardic Glassworks]

In short, I probably could have gone lower for longer. This piece started as basically a large pattern bar stacked 2 inches high. The long hold allowed it to level out and rid itself of most of the bubbles, the final thickness being about an inch and a quarter. It was then cut on the tile saw to one inch strips, flopped, then in for the second fuse. The first fuse cut like butter on the saw, so I did not suspect any anneal issues. The results of the second fuse were quite a surprise. Tim

[Rick Wilton]

Can't help... but I have to give you credit for posting this without a single swear word.

I couldn't make a piece like that and have it be ruined without venting.

Cool piece though.

[Laurie Spray]

I recently did a high fire Bubble Pot Melt where I dripped onto White 0013. Day after firing the entire layer of white cracked away from the flow leaving it intact. I am sure it was do to a shift.