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Old 02-11-2019, 03:42 PM
Rick Kellner Rick Kellner is offline
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Fire polishing in the kiln

Anybody have some suggested firing schedules for subtly fire polishing glass in the kiln?

I present to you a hypothetical scenario:

A piece blown from Spruce Pine SP87.

Cold worked with battuto style (or fill in the blank).

Final sandblast to minimize striations on cold worked facets.

Use kiln to soften up the coldworked treatment to something of a satin appearance, rather than a full gloss heat.

Thanks in advance for any advice.
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Old 02-11-2019, 04:31 PM
Eric Trulson Eric Trulson is online now
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I don't have any exact schedule for you (only just starting to do kilnwork myself), but a keyword that might help in your search is "edge firing". I'm pretty sure that's the kilnworker's term for a firing below tack-fusing or slumping temperature that just rounds the edges of a piece slightly.

I expect this is going to be a tough thing to do for most blown pieces. You're trying to heat up the piece just enough for surface tension to start glossing over the surface and rounding the edges, but not enough for the glass to start slumping and deforming. Not super difficult for a flat sheet of fused glass that's 100% supported underneath, but for blown glass where some of the lower portions of the piece are supporting a fair bit of weight from the upper portions, I expect you'll start to see deformation of the form before you see glossing of the surface.

That's a total guess on my part though, so please do try it out (on a test piece that you don't mind losing) and let us know what happens.

Edit: If you don't mind a slightly more hands-on approach, you could also try picking the piece back up from a pickup oven on a punty, then fire-polishing the battuto section directly with a torch or glory hole. Less automated, but more control, and you'd be in a position to recover from accidentally overheating the piece that way.

Last edited by Eric Trulson; 02-12-2019 at 10:06 PM.
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Old 02-11-2019, 04:54 PM
Eben Horton Eben Horton is offline
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Reverse your annealing schedule then bump up to 1075 degrees and hold. Drop back to annealing temp and anneal as usual.
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Old 02-11-2019, 06:56 PM
Kenny Pieper Kenny Pieper is online now
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this can only be done if the piece is relatively thick and the kiln is pretty powerful. you have to bring the piece from annealing temp up to a softening point, hold there till the surface starts to soften and then bring back down to annealing temp before the piece starts to slump.
Eben's suggestion of picking the piece back up and fire polishing in the gloryhole or torch is a good one
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Old 02-11-2019, 07:32 PM
Eben Horton Eben Horton is offline
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Sorry. I forgot to mention the pick up part.
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Old 02-11-2019, 09:38 PM
Marty Kremer Marty Kremer is offline
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I'm "curing" coldworked stuff (Bullseye) in the kiln from 1100 to 1300F with soaks from 10 minutes to an hour depending on the finish I want BUT this stuff goes back in the mold it slumped in originally; there's nowhere for it to move. I wish I could pick them up and flash them in a glory hole...
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Old 02-12-2019, 01:16 AM
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Quote:
Originally Posted by Rick Kellner View Post
Anybody have some suggested firing schedules for subtly fire polishing glass in the kiln?
.
I'd stick it up on a punty and flame polish it in the glory hole. Way more control vs. trying to do it in a kiln.
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Old 02-12-2019, 10:31 AM
Peter McCarthy Peter McCarthy is offline
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I don't know if it will get you the surface you want, but another alternative is to acid etch after sandblasting. I use Vari-Etch from His Glassworks, and like the satin finish it gives.
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Old 02-12-2019, 08:08 PM
Josh Bernbaum Josh Bernbaum is online now
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Rick, if you do end up going the fire polishing in the glory hole route, you may want to reach out to Adam Waimon. He's a glassblower in Providence, RI, and he reheats and fire polishes all of his pieces (made with SP batch) in the GH. He's a super open kind of guy, and would prob have some good tips for you if you go with that method.
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Old 02-13-2019, 01:07 PM
Rick Kellner Rick Kellner is offline
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Thanks for all of the ideas.

Reversing the annealing schedule and holding at 1075 sounds promising. I guess I have to experiment with hold times. Maybe a run of little test samples is in order.

I had read about acid etching, but it was in the context of nastier reagents. The Vari-Etch looks like another good option. Perhaps a bit more user friendly in terms of safe usage and disposal.

Was hoping to avoid picking up on a punty and fire polishing in the hole. Somehow my intuition is that the kiln could yield the most potentially controlled results, but I guess it might be a matter of establishing the optimal temps and hold times.

Did something similar in classes at Bullseye, but obviously that was with different glass and temperatures.
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Old 02-16-2019, 01:26 PM
John Riepma John Riepma is online now
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Here's a link to Mark Leputa fire polishing battutto in the glory hole after picking back up out of an annealer:
https://www.youtube.com/watch?v=Tn688MkP1bM
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Old 02-18-2019, 05:16 PM
Marty Kremer Marty Kremer is offline
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[quote=Rick Kellner;142769
I had read about acid etching, but it was in the context of nastier reagents. The Vari-Etch looks like another good option. Perhaps a bit more user friendly in terms of safe usage and disposal.
[/QUOTE]

Vari-etch in my experience worked ok on sandblasted fused BE but it didn't give a fire polish, it just smoothed the blast surface. It had an affinity for red opals.
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Old 02-18-2019, 05:59 PM
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Pete VanderLaan Pete VanderLaan is offline
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nothing with fluorine is friendly. Compare to "Littlefinger " in Game of thrones.
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Old 02-19-2019, 09:49 AM
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but he is...oh.
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Old 02-20-2019, 09:12 PM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is offline
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Rick- I question your assessment of sandblasting to minimize striations from your cold working, to begin with a good quality diamond wheel wont make any striations, and secondly a good wheel will give you a much better start to fire polish than a sandblasted surface will.
The blasting will take the sharp edges off scratches but any depth difference will remain- the blasting will remove equal amounts of material in the valleys as the mountain tops so to speak
Further I think your intuition that kiln polishing will give the most control is simply wrong, picking it up and fire polishing in a hole gives so much more control, although I think the optimal way is to heat your piece in the hole and then hit the surface at the bench with a gas/oxygen mix torch- then you see the progress of the polish very clearly as its happening, with complete control- no risk of over polishing away your cold work
That was a novel punty the guy did on the youtube movie- could someone explain how that is supposed to work- if that flat thing he made was actually the punty?
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Old 02-21-2019, 04:40 AM
John Riepma John Riepma is online now
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Michael, I wondered about that punty also and my guess is that the flared out shield is meant to reflect heat from the torch onto the engraving on the top of the piece rather than trying to get it hot enough to polish in the glory hole. I've also seen Eric Meek at Corning doing a grail demo and using a surface mix torch to fire polish the engraved areas as well as reheating in the glory hole, so I imagine that there are many methods to skin that cat.
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Old 02-21-2019, 07:35 AM
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Pete VanderLaan Pete VanderLaan is offline
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Quote:
Originally Posted by John Riepma View Post
Eric Meek at Corning doing a grail demo .
****
Sort of a Holy Punty? or did you men graal?
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Old 02-21-2019, 07:52 AM
Josh Bernbaum Josh Bernbaum is online now
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Quote:
Originally Posted by Michael Ahlefeldt-Laurvig View Post
That was a novel punty the guy did on the youtube movie- could someone explain how that is supposed to work- if that flat thing he made was actually the punty?
I've heard that called a "face punty". I think Mark used it there in the video because he didn't want to attach to the bottom of that form and it's easier than trying to size an incalmo-style punty to the rim of that vessel because you wouldn't have to size it or aim perfectly when sticking up the piece. And then it's minimal coldworkng afterwards if it's just tacked lightly to the rim there. This type of "face" punty can be very useful for making things like an open-ended cylinder or other shape that you might want to have openings on both sides. The diameter of the rondel should be a bit larger than the diameter of the rim of the piece. And if done right, you can chill and then torch that connection from behind the rondel/face punty and the piece will pop-off right at that connection which makes for even less cold working if done right.
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Old 02-21-2019, 01:54 PM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is offline
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That makes sense,- thanks
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Old 02-21-2019, 03:22 PM
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Paul Wheeler Paul Wheeler is offline
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Here's some fairly reliable fusing schedules including fire polishing.
https://www.slumpys.com/Company-Info...iring-Schedule
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Old 02-21-2019, 06:49 PM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is offline
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Holy graal- fantastic
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Old 02-21-2019, 06:51 PM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is offline
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Paul , it has absolutly nothing to do with what were talking about here
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Old 02-21-2019, 10:53 PM
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Sky Campbell Sky Campbell is offline
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I'm not sure what anyone is trying to say about the punty used. I do find it very interesting the way he made the foot for the vessel and applied it when picking up the piece for fire polish. That foot is part of the finished piece and really clever in my opinion. You would not be able to battutto the bottom of the vessel with that foot already in place.
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Old 02-22-2019, 12:15 AM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is offline
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Yes I was afraid of that too, how was it clever?
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Old 02-22-2019, 04:24 AM
Rosanna Gusler Rosanna Gusler is offline
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Quote:
Originally Posted by Paul Wheeler View Post
Here's some fairly reliable fusing schedules including fire polishing.
https://www.slumpys.com/Company-Info...iring-Schedule
Nope. Their schedules are notoriously bad.
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