Rapid fire polish on formed pieces

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#13599
Stephen Richard
Participant

The infgormation in this quote needs to be treated with care:

“The 20 minute hold in Segment 1 is to ensure the glass is a uniform 1000F temp. This is important because glass won’t thermal shock crack above that temp no matter how fast the temp changes.  The 1200 degree per hour ramp in Segment 2 takes the temp up too fast for gravity to have any significant effect on the glass. The 4 minute hold is just enough to fire polish all surfaces but not long enough for gravity to do anything destructive”.

Yes, it is important to have the glass at the same temperature throughout before any rapid advance in temperature.  However the temperture given is not a universally applicable one.  It depends on the glass you are using.  For some Bullseye and Uroboros glass 537C is their annealing point.  So you need to be about 110F above that to ensure the glass will not thermal shock.  For float you need to be at about 605C for your soak.

If the piece is already shaped, you need to do this in the mould.  This is hard on your mould, think about the firing requirements for your mould.  Also think about the physical nature of the effect of heat on glass.  Your slump termperature is below the fire polish temperatue, so it will deform.  This suggested techniques works only on flat pieces.  The schedule on 6mm pieces.  It needs to be adjusted for thicker pieces.

Dennis Brady often pushes techniques working at the edge of technical possibilities onto novice fusers.  Be careful.

Stephen Richard

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

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