Fire polishing - what is it?
A simple technique of returning fused glass items to the kiln to melt them just enough to give a smooth, polished appearance.
It's perfect for rounding the edges of fused pieces that have needed a little tidying up with a grinder/sickle stone or have been drilled.
To fire polish: put the fused item(s) back in the kiln (don't forget your paper/kiln wash) and ramp the kiln to 700C (1300F ish) and hold at that temp for about 5-10 mins.
That's it! Easy peasy.
If you plan on slumping, it is always better to fire polish BEFORE slumping.
http://www.warmtips.com/20060227.htm - read this @ warm glass
The "trick" to a successful fire polish firing is high speed ramping. Commando Raid. Run in, do the job, run out. Here's the schedule we've used several hundred times to do a simultaneous slump and fire polish on 2 layer COE 96 (temperatures F)
1. 400 dph to 1000F hold 20 (to ensure equalized temperature)
2. 850 dph to 1200F hold 20 (complete slump)
3. 1200 dph to 1300F hold 5 (complete fire polish)
4. FAP to 960F hold 60 (anneal)
5. 400 dph to 300F OFF.
To fire polish castings, you can ramp much faster - we usually go 1500 or 1800 dph - but high speed ramping during a slump firing can crack the mold.
For COE 90 glass, add 25F to all top temperatures.
For float or architectural glass, add 50F to all top temperaturs.