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Sunday, March 3, 2013

I give up

 I love throwing bowls, and I can make very pretty bowls. But I can't keep my kiln from killing them.
I got up at 7am and went down to open my kiln from firing yesterday. I knew it was either going to be really good or really bad, and based on past experience with this kiln I expected the worst.... and I got it.
 The entire load was a loss. My kiln is a manual gas Olympic kiln, and while it is fine for raku and bisque and my terra sig work, I cannot get a decent functional glaze firing to save my life. This is the last of many efforts. I'm not doing it again.
 The glazes I used were for ^5, so I fired to ^5 and I tried to cool it slowly, but again, it's manual and I was just guessing at what to do. These glazes needed a soak, obviously, but I don't know how to make that happen with this kiln.
 The Standard #266 clay bloated on some pieces, some pieces bubbled, not enough melt, some pieces melted fine but separated, the teal and purple ran like a mother at ^5 and there were bubbles that didn't settle on them as well. The glazes have potential for being really nice, just not with my kiln.
 I know all the reasons for what went wrong, just don't know what to do about firing in my kiln. Until I have a windfall and can buy an electric kiln, I think I am going to stick with terra sig, raku and maybe give it all up for weaving..... that went well over the weekend while my kiln fucked up all my hard work from the past month.
The lone survivor, a satin white matte on raku clay. A tiny bit underfired, but the only thing that looked decent.
I sat down and cried for a minute, then took a deep breath and kept myself from throwing things and smashing things. Then I came in from the cold.
I have two spring shows, I was hoping to have some bowls, but I won't. I will have some pendants and some barns. I want warm weather, I want clarity, I want direction. I have none of that right now. So I am going to weave and think about what I am doing.
and wait for Mercury retrograde to settle down.

27 comments:

Anna M. Branner said...

Ugh. Posts like yours scare me. My kiln was new when I bought it, with a computer to fire it. I just push the buttons for the cone 5 program and walk away. I know nothing about soaking, slowing cool rate...one of these days this disaster is going to happen to me.

I am SO sorry Tracy. SUCH a let down...like getting a hunk of coal for Christmas. Weave away to heal your heart and head!

Charles Hughes said...

Tracey, judging from the run of the glaze I think you hit at least cone 7. I used to use some 266 and found it really didn't tolerate much above 5-6 before bloating. I also think you're right about it needing a controlled cool, but it's so hard to judge what's happening. I have an Olympic gas kiln I was using for Raku, I thought about going to cone 6 was was afraid I would face the same problem. I'm guessing a pyrometer is the only way to really get a handle on the heat inside those little kilns. If you decide to try again, spring for the pyrometer, I'm guessing it will make everything better.

smartcat said...

I wish I could give you some advice. but I know nothing about gas kilns. Is there someone you could fire with so you could get some hands on experience?

If I lived closer I would say come fire in my kiln. Hope it gets better ((hugs))

Dennis Allen said...

Pottery is not for the faint of heart.Do you have cone packs to show us? I've never fired one of those updrafts but word is they are difficult to fire evenly.If you slow cooled from peak temp, you could have added to the heat work.Good luck figuring this out.You have a lot of talented readers to draw help from.

Tracey Broome said...

Hey ya'll thanks for checking in. Charles, the runny glaze is due to the fact that the recipe said it was for 04-5, which I thought was doubtful and it did run like crazy, but I was no where near ^7, I'm sure. Dennis, I don't use cone packs because there is no where to view them, I use my pyrometers and it works fine for most firing, just not functional glazes, obviously!
Thanks for your sympathy, ugh this pottery business.....
Xo

Laura Farrow said...

NNOOOO!! and damnit!! so sorry, pal. come put some in my electric anytime.. if you ever decide to make more. really. xo

Melissa Rohrer said...

Makes me sick to see those nice bowl forms going to waste. I am almost totally ignorant about gas kilns, but wonder if having cone packs here and there might be a good idea even though you won't see them until opening the kiln- just to get a better feel for how it's firing. I realize that's probably not the main issue, though. Sound like you need a gas kiln guru.

Tracey Broome said...

Nay on the cone packs, thats not really the issue. I needed to go up in temp a little higher and cool slower, I need patience at the end of a firing to sit and hold the temp manually and then cool it manually. I have no patience for this at the end of the day when it's thirty degrees outside, if I'm going to make functional pottery, I need a decent kiln to fire it in, that's the biggest problem. I sticking with raku for now!

k.houser said...

Sorry to see this post Tracey...I do understand the feeling. I would like to advise you against the 266 dark brown clay from standard. I have used it and had multiple problems and they were from an electric kiln. If you experienced bloating of the body you exceeded ^6...that clay doesnt like to get too hot...I think they are pushing it when they say ^6...plus its FULL of iron and if it is not bisqued to a higher than normal temp...there will be pinholing issues, blistering too. I have also gas fired that clay in a ^6 soda fire with full on crap results...that clay, electric ^5 or best yet...use another clay body. I did...Standard has better bodies that are not as dark but still nice...hate to see all yr work down the pipes...I feel yer pain!

oldgreymare said...

Have you considered beginning a campaign on Indiegogo? or a similar site? My daughter did one to raise funds for her required short film for NYU and raised more than her goal..In addition you have a blog to get the word out and you'd be amazed how many friends are happy to donate $10-20 and it all adds up and you might just be able to get your electric kiln?
just a thought.....
meanwhile... sorry about the firing....<3

June Perry said...

Tracey, I don't think it's your glazes. I think it's the claybody. Try a different body, same glazes and fire slowly. Don't fire down, but go really slowly (about 100F per hr) for the last few hours to avoid the glazes boiling so violently. Going super slowly avoids that and allows any bubbles to settle down without over firing. Use large cones and only fire till they point to 3 o'clock to be on the safe side.
I'm not sure how your burners plates are set, but make sure they're open enough to avoid any reduction if those are oxidation glazes

June Perry said...

PS: if the clay is bloating, it's either over fired, or it's contaminated with lower fired clay. That happened to me once with a cone 10 body contaminated with cone 04 earthenware. My supplier Georgie's in Portland, mixed the cone 10 without cleaning out the mixer after mixing a batch of earthenware. Of course, I was only refunded the cost of the clay and not the cost of my time, glazes and firing. :-(

cookingwithgas said...

stomp foot and insert bad words here. buggers... I am sorry.
If you want to make some work to fire in our cone 5 let me know and we could work something out.
Pottery is not for the weak is right.

Sherry said...

The disappointment of hard work, excitement at new pieces and then finding that it didn't work as it should. The blessing here is that you know how to do all the other work in our kiln and it fires well for that. What I take from this is that you tried anyway, even know that the kiln you have might not allow this to work the way you had hoped.

Sissy said...

Trace, I agree with June - it´s the clay body. My electric kiln works like a dream BUT it kills semi-porcelain and stoneware clays high in iron or grog. My heart stopped for a sec - what a disaster!!! Please don´t give up on bowls, the form is just perfect!

Tracey Broome said...

Hi June and K. My friend Barbara has used this same clay body/glaze combo with perfect results, that's why I was encouraged to use it. I know 266 well, used it a lot a few years ago so I know the glazes that it likes. Plus, I had two different clay bodies in this firing and both behaved the same. I'm pretty sure I was just at cone 5, I fired on the low side of 5 and my pyrometer is usually very accurate. Of course without cones, I'm not positive, but I feel pretty certain over firing is not the issue. I could have fired too rapidly, again with manual gas, there is sometimes a big variance if you don't sit at the kiln the whole time. The too fast firing is a very good possibility.iI've had this kiln for a long time now, so I know it's limitations, and this is one of them!
Meredith, been there done that, not interested in hauling work around to fire, but I do appreciate the offer so much!
Sherry, I'm trying to keep this same attitude, thanks for reinforcing it!
Hugs to all of you for your input and your sympathy!!!
Been thinking it over this morning and I am concluding that I fired too fast and the glaze didn't settle out at the end. If anything,I think it was under fired, the satin matte on the raku clay didn't bubble but it was definitely under fired. I know the glaze and the clay are compatible, it was just my error somewhere and using an updraft raku kiln does not help!
I'm blaming it all on Mercury, I am having crazy computer and camera issues today too!!,

Tracey Broome said...

Hey Sissy, I'm just about positive it isn't the clay body, like I said my friend Barbara fires this glaze/clay combo a lot with perfect results, she just has an electric kiln that she can program. Maybe I will raku bowls..... Thanks for your comment. Xoxo

June Perry said...

Tracey, if you are sure the clay is OK, then all I can think is that the bloating is caused by over firing, which puts your pyrometer as the main suspect. The large glaze bubbles indicate a possible too fast firing as well as possible over firing.
Stick a few cone plaques in there with cones 4,5, and 6 and fire very slowly. One of the problems with a dark body is the stuff released early on that can cause lots of irritating problems, like pinholes, etc. with glazes. So go real slow with the firing. I don't know how high you bisque, but with such a dark body, I'd fire a slow bisque to 04 or even 03 to burn off a lot of that stuff than can cause glaze faults later on in the firing. And lastly, don't pack the glaze firing too tightly.

Tracey Broome said...

Hey June, I bisque high 04, I already went down that road a couple of years ago with pinholes. I think you have it right with firing slowly, the kiln jumped up fast a couple of times while I was somewhere else and that seems very logical that it fired too fast, i didnt think of that when ruling out other possibilities. I'm almost positive it did not over fire. I raku in the kiln a lot and know its heat pretty well. The kiln was also packed pretty lose so that wasn't an issue. Thanks so much for all of these suggestions, I'm going with too rapid firing, I have had similar results when raku firing too fast.....

I'm liking the idea of a kick starter project for a new kiln:)

sheapottery said...

Tracey,

You fired much higher than cone 5. I can tell by the following reasons:

-- The bloating of your dark claybody. It's a fairly standard problem with dark iron rich clays and enough people have already chimed in on that.

-- Based on the pictures you posted, those aren't pinholes in the glaze, they're blisters that have broken open. They have sharp edges, right? Pinholes are smooth around the edges of the circle and happen because the glaze needs some time at a high enough temperature to smooth out at the end of a firing. Blisters only happen when the glaze is over-fired.

-- It's also unlikely that you'd have a glaze that runs like the blue/green ones did that also has pinholes like that on it if it were under-fired.

Glaze maturation and cone dropping are functions of time and temperature (heat), not just firing to a specific temperature. If you fired slowly at the end and/or tried to slowly fire down the kiln, you were continuing to add heat to the kiln and that means you reached a higher cone than your pyrometer indicated.

Technically, I fire to cone 8 in my electric kiln pyrometer/temperature wise), but because I fire very slowly in the final several hours to reach temperature and then slowly cool for several hours to get the glaze effects I desire, Cone 11 is completely flat when I put cones in the kiln to test the results. I suspect that I'm actually firing to cone 12 or maybe even higher.

When the pain and angst has faded and you're ready to try again, I'd suggest that you go out on the interwebz and find a good firing schedule to follow and try again. It's also a good idea to put some cone packs in several places in the kiln so you can see where the kiln is firing hot and where it's cold.

I know the heartache of an entire kiln of crap and you have my sympathy. Don't let it stop you from trying again.

Tracey Broome said...

I'm still not convinced this was an over firing, but again I can't be certain since I don't use cones. I don't have any spy holes so they are of little use except in this case where they would tell me something that would be nice to know. I only had one piece bloat and that was actually the raku clay. The colored glazes ran because they have a huge amount of melters and were said to be 04-6, I had a feeling they were going to run. I'm sure that glaze over fired, but not the white. The white was fine on the white clay body and it was fine on the insides of some of the dark clay.
I ramped up 270 an hour to 2205, that's what I have used in the past, but there were a couple of times that it shot up faster than that. I think I fired too fast.
The person that can help answer this is Barbara since she has fired this clay and glaze a lot. She will be over here next week and an take a look.....
Thanks for the input, all valuable information! Lesson here is cone packs help answer questions, haha! And, raku firing is more fun:) thanks a bunch!!!

June Perry said...

The firing down,depending on the schedule you used could have also added to it. The only way you can know for sure is by using cones. The bloating from what I understand is either due to body continuation or overfiring.
Pyrometers can go off at any time, and I never use it as my only tool. A little trick learned from my local supplier
Years ago, was to wipe the face of the pyrometer with some vinegar.

June Perry said...

That should have read "body contamination"not continuation .

Shannon said...

I know disaster is in the eye of the beholder, and I get the reason they are considered flawed but wow--do they look col with all the bubbles and spots. heh heh.

angela walford said...

Just as I read what everyone is saying trace... slow down and get some more air in your kiln... gas is a totally different fish to electric firing.. can you open up your air ports where the burners enter the kiln and even open up the gas to air mix on your burners.. Its reads like a dirty firing to me :P wish I could get my hands on your kiln but there are peeps closer to you than me!! hope you have some nice recovery time :))

Amy said...

what about using a couple of them as flowerpots? sorry for the disappointment! sounds so frustrating! ugh....

Fish said...

I wonder if you're using the dark clay 266. If so, I suspect it has manganese added to the body. That, as you know, will cause bloating and all kinds of odd glaze/body fittings.