Sunday, March 3, 2013
Thanks again bloggers!
I spent some time this morning weaving, and that settled me down a bit, and gave me time to think this through, absorb all of your posts and then do some reading in my pottery problems bible. I love this book and can almost always find the answers to my questions here.
It seems hard to believe that I over fired, my pyrometer just barely hit 2205f and I shut down the kiln. I was freezing and ready for supper. Is 2205 too hot? Of course, there is no way to tell if the pyrometer was correct, although it is very reliable when I bisque and raku fire. It is a likely reason for the bubbles though, it happens to me when I raku too hot, but it also happens when I raku too fast.... It would have been most helpful to put in cone packs. I don't use them and the one time I tried to there was no way to see them, there are no spy holes you can view them through, and they matched my pyrometer, so I thought I was good to go. It would have been helpful to have put them in with this firing to see if I did indeed overfire, which is likely.
The other cause for all of this is likely, as you said, rapid firing. The kiln jumped up in temp a couple of times and I got impatient at the end and bumped it up a bit. I ramped up mostly at 270 per hour. Is that too fast? This is the schedule I have used in the past.....
I do know that it's not the clay/glaze fit, I have seen these two together and they are fine.
oh and ps: I was wrong in my comment about the one bowl that bloated, that's it in the top photo, beautiful bowl except for a tumor on the inside, it was the 266 clay, not the raku, and yes, that clay body is prone to bloating, again, maybe over fired. I knew going into this that 266 is a problematic clay, but it is a beautiful clay body, I love throwing it and I love the dark brown raw clay, I do not love the problems it brings with it though. Maybe I will hand build some dishes that aren't glazed with what I have left of it......
Oh well, whatever, I'm over it, ready to move on. I have some tiles I want to make for raku and I have little houses and pendants waiting to be raku fired. I had this thing about bowls that I needed to get out of my system and so I did. I have no desire to make any more right now, maybe later...... for now I will just enjoy all of the great ones I have from other potters.
One other question: would it be worth a refire, or more fun to smash them with a hammer? I could take care of that right now!
Thank you all once again, I truly value your input!!!!!! Wise words and much appreciated sympathy :)
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You must be feeling better about this to some degree...your sense of humour is in full flight!! xoxo
I find most pyrometers to be less reliable the higher you go. I mostly only use them in wood firing, and only to know if the kiln is climbing or falling, as you can't trust them temperature readings.
I'm sorry you've had a bad firing. Believe me I feel your pain! Maybe put those pieces out of sight for a while? Once you've made some new work you can decide whether it's worth it to try and revive these.
Tracey, my latest bisque firing, I used the slow bisque firing schedule as listed in my Skutt manual; but just in case, I put a small cone 03 bar cones in the Dawson kiln sitter which I had installed as an extra safety feature when I purchased the kiln.
When I opened the kiln, the 03 was bent,and had tripped the sitter; and that was most probably because I did a ten or fifteen minute soak at the end, which was enough to take it up another cone.
And of course, glazes with a wide firing range can be problematical at the high end of the range, possible making them good candidates for winding up off the pot and onto the kiln shelf.
I just read both recent posts this morning Tracey. So sad to see the results from the firing of your lovely bowls.
The glazes look like they are potentially beautiful - I'm sure you won't give up on them.
I don't have the wealth of glazing experience that your wonderful bloggers here do, so I have no valuable advice to give, I'm sorry to say. Still a glaze newbie.
But, I can say that I have cried over myriad failed glaze firings and spent much time trying to work out what I was doing wrong. I have learned A LOT from my mistakes and lack of understanding - especially as I had no one to ask, so Google helped me out many times.
I still have a looong way to go and will never stop learning.
I never used cones initially, so didn't know my kiln wasn't firing to schedule - even though the controller showed the "desired" temps were reached.
But when I did start using them, I began to learn more about my kiln, and this helped me adjust temps and programme schedules to fit accordingly. Not before much pulling of hair and gnashing of teeth tho'!
I know you won't give up, because you love what you do - the beautiful results show that. And when we love what we do, we forgive ourselves (sooner or later) and try again... and again :)
And, as for Mercury Retrograde, don't get me started!
He's already played havoc in my personal life this cycle, and I don't appreciate his tricks. Very disappointed.
Roll on the 18th, I say!! :)
smash em trace, it's rather fun but only if you're in the mood!!
I sometimes, well, way too often, produce hammer-ware which goes, subsequently, directly into the trash but I have a friend who has a heap out behind her kiln shed where she throws (and leaves) the bad ones. Breaking them is satisfying one way or another.
Get a big hammer and go to it. Re-firing over fired pots, which I think they are, will not do any good.
Take the ten dollars or so for the re-firing and put it towards a nice bottle of wine which you can have after you're done with the hammer.:-)
Here is a short film on quality control by potter Jason Wason:
Alrighty, I will smash, haha!,!
Thanks, y'all definitely going for the wine tonight:)
Oh, man! That sucks that the firing didn't go your way. From firing electric and soda, I think that ^5 is closer to 2167 than to 2200. (We do an approx. 25 minute soak at the top that brings it to ^5 1/2.) Anyway, that dark brown clay is a bear to work with (I use something similar). Bloating has never been a problem but I've found that the glazes are a difficult fit.
If they're over-fired, re-firing won't do any good.
Pinholes might smooth out if re-fired. Over-fired blisters won't.
If you under baked a cake, you could possibly put it back in the oven and maybe get it to come out right. If you burned a cake, putting it back in the oven won't help, even if you put more batter on it. Think of it like that.
my cone 6 firing reaches 2232. I only do slow fire--these days but will experiment with medium soon. so your highest temp isn't too high for cone 6.... maybe it's the pace at which the temp rises? hmmm
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