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Firing Log

ancient kiln | 21st century logbook

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April 2, 2006

Firing Update, #6

Filed under: anagama, 6th,Firing — odin @ 4:00 pm

The firing is over. I called it this morning (April 2, 2006) around 5:00 am mostly because there was a collapsed shelf. It wasn’t a failure though. I finally feel like I can fire the kiln. As I spent some time peeking in the kiln, I realized that it fired extremely hot and glassy. The walls have become glazed to an extent far in excess of the first five firings combined. I was amazed as I looked inside when I saw a blob of glass drip down from the ceiling like a big spider dropping from a thread. The bead dropped and the thread just hung there for ages.

I also understand the kiln monitor issue. The probes are encapsulated with glass. This either insulated the probes or affected they’re sensitivity in some other way. This is the last time I let a number on the monitor influence my thoughts. I still like to have the monitor, because I can correlate what I see from the chimney and hear from the kiln with whether the temperature is rising or falling, but achieving any particular number is completely irrelevant.

Talk about hot too — the shelves look like lasagna noodles, thin pieces unimaginably warped, as if they melted over their wadding. I suspect a 25% retrieval rate will be generous. Despite the obvious failures in these regards I am ecstatic. I wasn’t positive I could fire this kiln to a glassy result.

Last firing, I made the firebox area a little bigger and results improved from firings 2-4: the 5th firing had decent glaze and a lot less black crud than those intermediate firings. In this firing, I made the firebox bigger still (too big) and it got even better. Obviously, the sweet spot in this kiln is somewhere in the middle and I’ll be able to hit it next time. Now I can focus on other issues.

Stacking shelves is difficult beyond belief in this kiln. The obvious solution is to make stuff that fits the kiln better and doesn’t need shelves. I think in the next firing I’ll make only two rows of shelves — the rest will be pieces made to fit the size and shape of the kiln at the various levels. I already have some ideas for things to go there and I’m very excited. Can I wait till September?

As for a kiln monitor to use till I’ve trained my eyes and ears to be all I need, I think I’ve thought of the perfect solution. I’ll make a thick rectangular slab shaped piece with a built in prop so it can be stood on edge easily. At the top, I’ll put in some gravel size feldspar chunks. When those melt, I’ll have glaze. More pulls too. I suppose I’ll have to have a center shelf right behind the firebox to raise these test pieces above the coal bed — perhaps a pillar of bricks would work best. A 9″ square pillar 18″ high will not fall over.

Anyway, now for the really hard part. Cleaning up the kiln site, and even worse, waiting for the kiln to cool! Maybe I’ll go pitfire something in the hole I dug getting dirt for the ceiling.

Firing Update, #5

Filed under: anagama, 6th,Firing — odin @ 1:45 am

11:06 pm, April 1.

I’m hoping if I write a bit, I’ll be able to stay awake till dawn. At this point, it isn’t clear to me that I’ll make it. Exhaustion is catching up with me. OK, take a deep breath. This is fun, an adventure. The sort of thing that makes good stories later. I enjoy this. The longer I stay up, the better bed will feel.

So I need some topic — how about “worrying”. I’m a worry wart (wort?). There isn’t anything I can’t worry about. A glass half empty guy and I’m noticing that the glass is cracked and leaking.

So today I gathered up all the bricks I could find. I don’t have a ton of leftovers. I came up with 24 bricks though, enough for four courses at the top of the chimney. So I raised the chimney 10 inches this afternoon. Here’s what I was thinking — the wind that I’m missing helps increase the draft. If there is no wind, increase the chimney.

So I do that (as if 10″ on 96″ chimney will have a significant impact) and immediately start worrying about black crud on the pottery. Here’s the worry:

I’ve been thinking about building a wood fired bathtub out here. FYI, my last shower was Tuesday, so — yeah, it would be nice to be able to take a bath. I won’t go into the plans but it involves a natural siphon, metal cow trough, old stove, and some piping. Anyway, in my research I ran across some wood stove discussion on the net in which it was mentioned that controling the burn rate of a stove by the air vents instead of a damper causes a sooty chimney. Well — this kiln has no damper, the air vents control the burn. So I was thinking that may be the cause of my black crud. Seems the same principles would apply.

So, to come back from that tangent, I no sooner had 10″ more chimney when it hit me — that effectively makes my air inlet smaller and there might be soot buildup. I’ve been concerned about that for the last few hours. I took off one course a little while ago — I’ll probably take more off later.

All this because the kiln monitor doesn’t want to break 44 mV reliably, and instead hangs out at 42-43 mV and I want to go to 50. Drat! But make that a real swear word.

On the other hand, there are two loose bricks on the bottom side of the upper fire mouth — the stoke hole. They’re constantly being knocked in a little and then I pull them back with the hook on the pole if I remember. The tips of these bricks have become glazed. If I can glaze bricks that have air coming in over them from the edges around the door to the firemouth — things should be OK inside the kiln. Really. I tell myself this but I still worry.

Well, I haven’t checked my email in two days and I’m worried about what disaster will have happened at work, so I better do that now. Besides, I need to go fill the wheelbarrow again. At least I feel “awaker”.

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