How to prevent "dog boning" slumping a deep dish mold

[John Weidert]

I am getting a "dog bone effect" when using a 10" x 13" deep dish mold. The mold drops 1 1/2" and has a flat 2" web on all four sides.

The slumping results look great with the exception of the dog boning on the four sides. The 10" sides do not show much dog boning, but the 13" sides show a distinct "dog bone" effect.

Is there a way to minimize this dog bone effect? I am using bulls eye , coe90 glass. There are two pieces of the glass fused together and then slumped.

Thanks,

John Weidert

[Brad Walker]

Rectangular or square molds that have steep sides or a deep drop are prone to dogboning. It can't always be prevented, but it can be minimized by slumping slower and at a lower temperature or by using more than two layers. A thicker piece will be less likely to dogbone, as will a piece that's held longer at a lower temperature. But it's the nature of some molds that you will get some dogboning no matter what you do; you can reduce the extent, but it's difficult to prevent entirely.

Another comment: usually, the molds that have the worst dogboning are molds that were not made for slumping glass, but are simply bisque ware with a hole drilled in the bottom.