Refiring pot melt

#12218
Stephen Richard
Participant

“I had one pot in the center as well as two on either side- I center pot was
large enough to hold the amount of glass I needed. Before I fired I was
concerned about that.”

My question was about the centring of the pot above the circular dam.  If not centred, It can leave you with more glass on one side than the other, if the high temperature soak is not long enough to  allow a flow to equalisation.

“I now understand the need for a slow advance and how
you came up with that.”

OK. Good

“3 more questions: Can I do this on thin fire paper
since I am firing to 1500 or do I need to prepare the shelf as I did for the
pot melt?”

I don’t now how you prepared the shelf, but by implication, you used batt wash.  If so, yes you could use thin fire or a new layer of batt wash.

“Do I need to go on and remove the kiln wash that is on the
underside on the piece?”

Yes.

 

“Do I need to dam it again? ( I think yes).”

Yes if you want it to be the same size.

“I am so
afraid to fire that thick a piece w/o one and I have never done a pot melt
w/o one.”

The major danger is that there will be too much glass and it will overflow the shelf.  But there is a good pot melt calculator on this site (under tools, I think) that will tell you how much glass you need to get a disk of given dimensions.  I do all my pot melts without dams.

“My firing schedule for this piece was 600/1000/20 250/1100/20
450/1700/90 9999/1540/45 then to 900/120 and a conservative cool down”

333C/hr seems a bit fast for the ceramic pot, but if it is surviving, fine.  The 20′ soak at 538C seems odd and unnecessary. Why you slow down to 140C/hr for 55C after 538C is also a mystery to me. If you want a soak to let the air out from between the glass pieces, this should be done in the region of 650- 677C with a soak of ca. 30mins.  In general people speed up as the glass gets warmer.  You seem to be slowing and then speeding up, but not to your initial rate of advance of 333C/hr.  Odd.  I think 838C (1540F) is too hot for your equalisation temperature, try your full fusing temperature instead.  I would use the Bullseye schedules for annealing thick pieces and go from your equalisation temperature afap to 482C and then apply the schedules.

“The first two this week have alot of popped bubbles on surface, not over an 1/8
diameter. Do I refire with top side up to a full fuse1500 with a dam?”

A good strategy is to clean the bottom and turn it over and fire, although I would normally not go much above a fire polishing temperature.  In this case you will want to go high enough to allow the glass to flow.  This means that more bubbles will appear and break on the surface.  It is part of the nature of the being.

“Using thin fire or heavy kiln wash?”

You can use either, although in this case I would use batt wash as you want the glass to move and that might pull the thinfire into the glass.  I – unlike most people – do not use thick layers of batt wash.  I spray the wash onto the shelf until it is uniformly pink.  This is not very thick.  All you are trying to do is to keep the glass and the shelf separate.

“Thickness 1/2 inch.”

?

“Or do I flip it over and fire to 1500. I would guess at a soak of 30 min”

I think you are asking whether to clean the present back, turn it upside down, dam and then fire slowly to 815C.  If so yes, but you will need a much longer soak to allow the glass to move and become approximately the same thickness all the way across.

“The need to redM is always confusing to me.”

Just as using the imperial system is to me.

Thickness again is 3/8 [10 mm] on one and 1/2 [13 mm] on the other.

So the difference is 3 mm (not the 7 mm you indicated it might be)  This means that you could fire as for 15 mm [5/8 inch].  This would mean an initial rate of 90C/hr to 250; 115C/hr to 500; 150C/hr to top temp. [no bubble squeeze required].

“The firing schedule on the ” bubbled” pieces were pretty much the same except

700/1700/90 & soaking at 1500/60″

This would indicate to me that you have not yet settled on a firing schedule.  Are you keeping notes so you can compare the results of different firing schedules on different amounts of glass and of different colour combinations?

I really appreciate your good explanations and advice. It is nice to know these forums are here and people are so

willing to take the time to answer these questions. Thanks Susanne”

 

Also note that unless you have your shelf perfectly level, the same un-eveness will occur again.

Stephen Richard

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

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