Last kiln load cracked me up. Literally. Crazing was everywhere on the pots with clear glaze.
I have two possible reasons:
1. Switched from Aardvark's Bee-Mix to Laguna's B-Mix... Would that make THIS difference?
2. Unloaded a hot kiln... But I really didn't think it would matter THAT much. Jeez...
I've been sitting with this for a couple of days, reluctant to glaze anymore with the same clay/glaze and have the same problem repeat itself. Kind of paralyzing.
Then I read about it happening to someone else who unloaded a hot kiln. Like in her situation, the pots looked great then and even later that evening. In my case, I even put them out in the gallery space. Then, the next time I took a look at them - OUCH!
So, my plan now is to re-fire, wait a very long time before unloading and see what happens.
If that doesn't work, I might actually do more test tiles. Imagine that.
16 comments:
Ok, I am a babe in the woods, but does crazing have to be bad? I kind of like the look of it.
Sorry about the crazing--I've had that happen a lot from unloading a hot kiln. Do you know what the temp was at unloading?
definitely could be from diff. clay body...maybe it doesn't shrink as much, and yes, we want too know..how hot was the kiln?..sorry about the "craze-y-ness"
I think I read the same story you did. She said it was fine after refiring-but-that is related to her opening the kiln very hot she thought. If your crazing is from different body-then different matter. The clay body does make a huge difference in my experience. I had to try about six bodies before I found one that my celadon did not craze on.
Hey Linda - Yea, if it was the exterior of a vase or something like that, I could go with it. Just put some strong tea over the top and it would flow into the lines and stain the pattern. Would be pretty. However, it's supposed to be food-safe ware (plates, bowls and such) and crazing to this extent is not good. Plus, I'm really trying to have the finished pieces end up to be what I was intending. Though I'm totally cool with creative surprises, this was not what I had in mind. Yikes.
Hi Ben and Jeff - I didn't note the temp (I know, I know, I know... screwed up) but I'm thinking it was like 270 or maybe 340?... Hot enough that I had to use towels on my hands to remove shelves and ware.
A friend was with me and I was all distracted, yacking away. I do recall thinking, I shouldn't be doing this. And then, rationalizing, well, it's not THAT hot. I take things out of the (kitchen) oven when it's this hot. Surely, this won't be a problem...
Deborah - I can't imagine having to go through six clay bodies! I'm just not that patient. Whine. Whine. Whine... (I'll grumble for awhile and then I'll eventually buckle down and do the work.) However, I am hoping for a turn-around of events by re-firing and seeing what happens with a slow cool and no early opening. Not even a peek.
You must be referring to Chi's post the other day...
It's worth a shot to refire and if it still crazes, do some tests with different clay bodies or tweak your glaze recipe to change the expansion ratio of the glaze to see if that helps.
Sadly, every damn thing makes a difference. I really think most pots are happiest, and this is based on experience, if they are left to cool extra hours until nearly down to room temp. Also, a higher bisque can help: I go to 06 now. AND some glazes tend to do that on some pots with some clays. Years ago I had a good glaze for terra cotta, but it shivired right off white clay pieces! It was horrible (shivering is an extreme crazing---the glaze crackles and some falls off the edges).
Back to the drawing board, eh?
Oh geez, plates must be food safe - what was I thinking. I remember one community glaze load in a large gas kiln at friend's house, we opened up peep holes so we might peek to see how the glazes turned out at about 180 or so on a windy day and we heard a popping noise and plugged them up real quick. Then we waited till later that evening to unload. We didn't have any problems on anything we could see, but I always wondered if something in that load might have cracked later on.
Hi Cynthia - Yes, it was Chi's post. Sounds like she had success with re-firing, so I'm going to give that a shot. Sometimes, it just seems like it's a process of elimination. Thanks for visiting my blog. I really appreciate your input!
Hi Gary - Thanks for your suggestions! I read that about going to a higher bisque on Clayart too. I've just been going to 05, so I'll change up and see what happens. I'll be reporting back...
Hi Linda - I thought about your initial comment later today. I was showing someone the studio and he was immediately attracted to the crazed plates I had stacked in the back (awaiting re-firing). He liked them, and pointed out the pattern to me (as if I needed that to be pointed out!)... To him, they were a good thing. Anyway, I explained what had happened and that I was going to re-fire.
I'm no expert, but high 200's does not seem unreasonably hot to unload-meaning I don't think it should lead to that problem and I'd be inclined to think it's the change in body. Someone once wrote that if a glaze was going to craze, it crazes. How to say? If indeed it is temp. related, bringing them from the kiln hot might encourage something to happen more quickly than it is eventually going to anyway. I have made pots and months later, and in one case a couple of years later, noticed that they had started crazing. I wonder have you seen one of your pieces with this glaze a couple of years after you made it? Just a thought. Sorry my comments can be a little wordy.
Hi Patricia-I hope I don't sound like a know-it-all. You probably already know this so forgive me, but if you go to 06 like Gary instead of 05 as you currently do, you are firing LOWER. Maybe you are intending to go to 04? I personally bisque to 06, but I like my bisque softer and more absorbent.
Hi Patricia,
Thanks for your comments on my blog.
I liked your famous maker challenge... very fun!
I think your problem is the change of clay. Another possibily could be that you applied your glaze too thick. Some clear glazes tend to craze when applied thicker
Best to you. Lucy Fagella
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