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Old 07-21-2017, 03:14 PM
Rick Kellner Rick Kellner is offline
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Gas annealer lowdown

Any pointers on annealing soft glass with gas fired kilns?

Off the top of my head, I think something like a Partlow gas throttling valve could be really useful, for maintaining a set point temperature easily. Could you just shut off the burner after the hold period, and successfully anneal, depending on the insulating properties of the kiln? Perhaps this wouldn't get the temperature profile curve within range.

I know that setting one up like a gas furnace would facilitate the highest level of temperature/time control, but that sounds like overkill to me.

Would be nice to achieve something in between old world primitive annealing in a little chamber above the furnace, and a complete, state-of-the-art computer controlled rig.

What type of set-ups are folks using to anneal with gas ovens?
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Old 07-21-2017, 06:50 PM
Dan Vanantwerp Dan Vanantwerp is offline
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Hi Rick, I worked with Michael Hermann in San Diego to help build some of his equipment. He had an old ring burner that we set beneath a vertical annealer that was probably 4' wide x 3' high x 3' deep. This was an outdoor, covered venue...no need to worry about venting. The entire annealer was stuffed with probably 4" of blanket and had a soft brick floor. Michael set up an old needle pyrometer to dial in the working temp but when he went to anneal he just shut off the gas.

http://hermannlunnglass.com

Michael and Gina are damned talented and Michael's work, in particular, is very fine (goblets and all the Lino inspired designs). That he trusts this setup would be good enough for me if I worked there.
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Old 07-21-2017, 08:15 PM
Tom Fuhrman Tom Fuhrman is offline
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Check with some of the Europeans. I've seen these in many of the Italian and Czech studios. They've been using this type of annealer a long time.
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Old 07-21-2017, 08:39 PM
David Russell David Russell is offline
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Harry seaman at corning had one running about 10 or so years ago. Made for Elio.
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Old 07-22-2017, 08:15 AM
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Pete VanderLaan Pete VanderLaan is offline
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I ran one over 30 years back. It had a really tiny venturi pilot and a mid sized venturi for the main burner. It was behind a bagwall and was on an old love controller. The controller supervised the main burner solenoid which was turned on and off but the pilot relit it each time. It was really nice for colors that wanted a reducing atmosphere in the lehr. It was also dangerous as I recall and I would not be likely to try it again. It was also disconcerting to have stuff blowing at you a bit when you opened the door.
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Old 07-22-2017, 08:48 AM
Nick Delmatto Nick Delmatto is offline
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I've been gas annealing since '82. All my ovens have false floors like a pot furnace. I use a venturi burner system & control the temp by watching it while I work. After soaking, I turn it down for a few hours to 750, then shut it off. I have to crack the door before I go to bed so it's cool in the morning. The only drawback is I can't lay pieces down. It's old school & I love it.
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Old 07-22-2017, 08:50 AM
Nick Delmatto Nick Delmatto is offline
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Also, the false floor is silicon carbide shelving with fiberfrax board on top, sometimes a thin kiln shelf on top of the fiberboard.
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Old 07-22-2017, 09:39 AM
Travis Frink Travis Frink is offline
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Quote:
Originally Posted by Nick Delmatto View Post
I've been gas annealing since '82. All my ovens have false floors like a pot furnace. I use a venturi burner system & control the temp by watching it while I work. After soaking, I turn it down for a few hours to 750, then shut it off. I have to crack the door before I go to bed so it's cool in the morning. The only drawback is I can't lay pieces down. It's old school & I love it.
I know a couple people running systems like this here. They tend to do thin production items with few bits added. I've seen some questionable "annealing" out of said ovens as in some things break... days, weeks, etc after they are made. Other work gets slumped if it the temp gets too high cuz the furnace burner is working overtime for some reason ( the annealer is heated with flue exhaust after it exits the recouperator).

Another close friend who used to do this same thing later added electric elements (after noticing that some work was breaking!) to finely control cool down. It is still largely heated from the furnace flue heat. A lot of complex work comes out of this oven with no problems at all. I personally would try to add some elements like this or a burner on a controller if possible.

The hot air flowing through some of those gas annealers does seem to circulate the air which seems to anneal things a lot faster than a closed (no circulation) electric annealer.
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Old 07-22-2017, 10:07 AM
Nick Delmatto Nick Delmatto is offline
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Travis, I'm not recuperating. My annealing temp for hollow ware is 900 F but I take it up to 925 F for paperweights & I can get a rougher bottom but I grind it out. I've had no under annealed problems with my system. It's my understanding that bottom heated ware is annealed more completely.
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Old 07-22-2017, 10:57 AM
Travis Frink Travis Frink is offline
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Quote:
Originally Posted by Nick Delmatto View Post
. It's my understanding that bottom heated ware is annealed more completely.
Interesting. Thanks.

I'm sure your system works and your experience over so many years is proof. I respect that.

What do you if you are making more complex objects (lots of bits, differences in thickness throughout the piece, etc) or one-off items that might be quite different from the items you usually make?
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Old 07-22-2017, 12:01 PM
Nick Delmatto Nick Delmatto is offline
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Travis, I'd keep it at 900 & a longer soak for variable thickness. Thin stemware would be 890 F. I'm using 89 COE factory clear cullet if any of these #s sound weird to you all. I bought a life time supply of cullet when Lancaster Glass (Ohio) went out of business in '08.
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Old 07-22-2017, 12:53 PM
Steve Stadelman Steve Stadelman is offline
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I built a hybrid for Donald Carlson that had a pilot for reduction and ni chrome heaters for the heat control. It was to provide reduction for color maintenance. Don't use A1 in a reducing atmosphere.
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Old 07-22-2017, 01:15 PM
Eric Trulson Eric Trulson is offline
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Quote:
Originally Posted by Steve Stadelman View Post
I built a hybrid for Donald Carlson that had a pilot for reduction and ni chrome heaters for the heat control. It was to provide reduction for color maintenance. Don't use A1 in a reducing atmosphere.
That's really cool. Did you use bare coils of nichrome wire, or the oven style with the ceramic powder insulation and metal tube on the outside? Any idea if the element life was shortened appreciably?
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Old 07-25-2017, 02:21 PM
Rick Kellner Rick Kellner is offline
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Great dialogue here. Thanks to everybody for all of the information and anecdotes. It's given me some ideas of things to try.
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Old 07-25-2017, 03:23 PM
Eben Horton Eben Horton is offline
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I used to occasionally blow glass at a studio that had 2 annealers that were heated by flue heat. They were on each side of the furnace and the flu made a "Y" shape out of the back of the furnace. The floor of the annealer was a 2" thick slab of mizzou and there was a vent on the ceiling. Baffles were used to close down one side while the other side was being used. It worked great. The mizzou slabs acted as a heat sink and would provide a nice steady 12 hour turn down. The thicker the slab the longer the turndown and vice versa. Sorry for any typos- I typed this on my iPhone.
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