shari
New Member
Posts: 7
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Post by shari on Feb 11, 2017 9:56:08 GMT -6
Thank you for this forum! I have been watching from afar and am trying to absorb as much as I can. The detailed discussions appeal to my inner geek. I am relatively new to the world of crystals but am addicted; as are most.
Hello to Jerry S, Kuba, Ginny and Jose! You have all helped me immensely! My ultimate goal is still crystals in gas reduction. Jose makes it so easy and I am still struggling with my gas kiln. I wish I didn't have a full time "other" job and could dedicate more to my pottery. Pottery is my fun, relaxation, and challenge.
A question to anyone reading... I'm trying to make my mind up on going to Portland NCECA. Will there be material or presenters specifically on crystalline work? I scanned the site and didn't see anything that jumped out, but there was so much going on.
Thanks to everyone who contributes to the forum. I hope I can be a contributor at some point too.
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Post by tileman2 on Mar 2, 2017 17:07:20 GMT -6
Hi Shari:
I attended NCECA in KC this past March, and enjoyed every minute of it. I had arranged to meet and study with Ron Roy beforehand, and spent most of my time hashing over the fine points of clay formulation. I had to leave midway through it due to prior obligations, so I did not get to take in everything, or meet many people. One person of interest was Marcia Selsor: a retired professor of ceramic arts at the University in Billings. She had retired to Texas, but just recently moved back to the Red Rock area. She did her degree work in crystalline glaze at the University of Illinois, Campaign back in 1973. She still fires crystalline every once in awhile, but she primarily does raku and obavara firings now. If you would like to speak with her via email, I am sure I can get that arranged for you? She is an extremely kind lady, and is currently doing a series of online education series: which also might be of interest to you?
The other thing about NCECA, is that all of the tool makers, clay and glaze makers, and a host of others have kiosoks set up for you to review their products. Even better, they sell off their demo products CHEAP... I bought a Shimpo wheel while I was there.
Tom
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shari
New Member
Posts: 7
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Post by shari on Mar 4, 2017 8:34:01 GMT -6
Tom, thank you for the reply. Yes, I would love to reach out to Marcia and appreciate your help. Sometimes it is amazing the resources around us we don't know about. I've backcountry horse-packed in her neck of the woods and it is a beautiful part of Montana.
I also see there is a book library to be at nceca. Know of any gas reduction crystalline books that might help me?
My latest theory is that the air movement in my gas kiln is killing the crystals. Do you think that is possibility? I have a geil that fires relatively evenly, but perhaps turbulent. I am experimenting with blocking off the sides of my shelves to create a quiescent zone. The sheltered pieces and flat pieces (outside the shelter) grow crystals more reliably. I also get bubbles on the pieces outside the quiescent zone. I don't know if it is a secondary affect because of how heat work is built or cooling slowed, but the cones inside and outside the shelter are consistent. I need to keep trying since it is hard to keep all other variables constant in gas. Any thoughts are appreciated.
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Post by tileman2 on Mar 4, 2017 9:35:43 GMT -6
Shari:
Check your PM messages: Marcia sent you an invite to join her. She is a very smart cookie in all things pottery. I seem to remember her saying she did her degree work on crystalline glaze in a gas kiln back in 1973. I fire only electric, so I cannot offer you much help with gas firing. I do know crystalline glaze requires an oxygen atmosphere, or at minimum a neutral atmosphere in a gas kiln.
Tom
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Post by billcampbell on Mar 4, 2017 10:09:28 GMT -6
Shari
I fire a gas kiln several times a week without a problem. That has not always been so.
After getting rid of my reducing atmosphere, everything began it work out.
Play with the gas to air settings until you have a blue flame. Make sure that your damper is open enough for all of the gas going into your kiln is burning. You can overdo that and you will get air entering your kiln and cooling it off. This is a tricky part to get right.
The issue with the blisters is, the reduction of Zinc oxide. When zinc oxide is reduced, it changes into the metal zinc. that metal boils at a low temperature, and causes blisters. Once that it starts to boil, you may fire it forever without losing the blisters,
Fire your kiln empty, and keep an eye on what it is doing. any yellow flame will tell you that it needs more air to get to a neutral or oxidizing atmosphere. You shouldn't need any kind of "bag wall" to stop the turbulence. The kiln that you have is heated two ways. It is heated by radiation, like an electric kiln, and by convection. That is caused by the turbulence. That is a good thing. It allows the pots in the middle of the kiln to be heated the same everywhere in the load.
Bill Campbell
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Post by Arnie Benton on Mar 4, 2017 14:19:04 GMT -6
Hi Shari -
I agree with everything Bill says - only I had so much trouble getting the kiln to stay in a neutral atmosphere that I gave up on it. In an oxidizing atmosphere the kiln actually can cool rather than heat - or it takes what seems like forever to heat up to cone 10. In a reducing atmosphere the zinc boils off, so no crystals and craters.
Hopefully you'll be able to find the settings that will allow you to have Bill's success. In my own experience that requires constant attention and adjustments, even with the electronic controls. I also had major problems with post fire reductions in the 1300 to 1400 F range - because it's very hard to get a reducing atmosphere at that temp - especially because the safety settings don't allow you to close the damper enough. I had to turn the gas way up, which would cause the temp to rise higher than I wanted.
So I gave up and switched to electric heating -
Arnie
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Post by jfox on Mar 4, 2017 15:21:08 GMT -6
I switched to firing in a gas kiln a a few years ago so i could use a bigger kiln ,had all the same problems till i installed some blower burners now i can climb nicely in neutral. still get some burnout around the edges but it lets me fire more and larger work. downside is it not programmable so i have to fire manually
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shari
New Member
Posts: 7
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Post by shari on Mar 9, 2017 20:42:03 GMT -6
Thanks everyone! I will try with an empty kiln and change one variable at a time. I have an oxygen probe and can confirm (although only one spot) that I always get minor reduction. If med-heavy reduction is say 110 on my probe for a given temp then when climbing I can creep up to 10 and sometimes 15 when trying to stay in oxidation. Running when cold or door wide open is 0. Do you think 10 or 15 is significant? Sounds like it might be...
New enough that I didn't realize the zinc changed state and boiled off. Thank you for that knowledge!
If I can successfully get to cone 10 without reduction, at what temp or cone is it safe to post reduce? I think I'm looking for what temp does zinc not go to zinc metal in reduction. Correct? Or what would be a source to look that up.
Thanks again!!
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Post by jfox on Mar 10, 2017 9:27:34 GMT -6
if all the zinc gets bound up in willimite your safe but i havent found anything i liked from highfire reduction and i think the best results come going
all the way down to 1350 to 1450 F
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shari
New Member
Posts: 7
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Post by shari on Mar 10, 2017 19:13:01 GMT -6
Thanks again. I will try! Jim, do you fire with an oxygen probe or know by flame and pressure. I'm curious how precise I need to be?
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Post by jfox on Mar 10, 2017 19:25:55 GMT -6
I dont use one i put enough gas with damper fully closed until i can ignite (with a torch) the exhaust from a small port at the bottom of the kiln and it will stay lit. i give it 10 o r15 minutes like that. be careful relighting the kin at that temp. you can see some of the reduction stuff in the links below
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Kuba
Full Member
SztukKilka in Old Formu
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Post by Kuba on Mar 11, 2017 8:51:02 GMT -6
Hello Shari  Wish You luck with Your gas kiln. Check @ I sent You something. |
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shari
New Member
Posts: 7
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Post by shari on Mar 12, 2017 13:41:37 GMT -6
I was looking back at my data from a run in fall that I have questions on as far as temp, reduction, and crystal growth. I'll post it in the Beginner's section if people wouldn't mind giving me further thoughts with specifics. Thanks! Shari
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Wish You luck with Your gas kiln. Check @ I sent You something. 