Pit fire done

Tell us! Tell us! This is so exciting.... hopeless, hopeful...... I wish you at least a few beauties to make the learning more fun.

Catherine in Yuma, AZ

OK - so I didn't take anything out because everything was too hot still, and left it for another day: mistake, as the evening's thunderstorm filled the pit with water. I was not worried because I figured everything would be fired, and should not fear the water.

Anyway - Yes - some beauties, some very strange things too. Before the beauties, some questions.

I found a large amount of the sawdust in pristine, unburnt, unscorched condition, and even some of the newspapers which were used to keep the copper wire in place unburnt - black, but clearly identifyable as newspaper.

My favourite piece fell apart as I lifted it from the water, and the inside (under the wonderfully black surface) was leather hard clay. It had not been fired at all, and the thunderstorm had soaked it.

How is it that with so much heat coming off the burning stuff, things left in the pit for 48 hours come out just blacker, but not fired? Obviously not enough air was getting to them to let the sawdust / embers around them burn properly, but how do I remedy this?

Should I break apart the stuff that I thought did fire ok to check that it has fired indeed? Some of the ware does rign out when struck with a key or a coin, but not all of it.

The slips I used performed ok, given it was a test firing, and I think I understand the behaviour of burnished when compared to non-burnished. I don't understand why what broke, broke, and why what didn't, didn't.

The copper wire produced metallic silvering on the pots, which was fun.

The successes were the wonderful black shiny surfaces where the burnished pieces got very reduced. I like the look of that.

Basically, I have to do it all again, either with a grate to keep the pots slightly higher in the pit, or with air holes coming into the bottom from outside the pit. I want to get another pit fire done better, before moving onto making a simple brick kiln like on sidestoke.com/firstkilns/firstkilns.html (thanks for the link, Graeme).

Last question - should I put the blackened but unfired clay into the re-claim bin, or should I throw it out?

Stelios

Stelios, it has been my experience from raku work that if a piece is exposed to heat, it is no longer good for reclaiming as clay. Might make good grog when ground up if it got up to bisque temps. Blackened clay will have a large amount of carbon in it. Will cause unpredictable results (in both body and glaze) if re-used. It sounds as if the sawdust was too tightly packed, which is why some of the pots were "insulated" from the fire, and some of the sawdust and paper did not burn at all. You might try refiring any pieces that, as you say, do not ring out. you might be surprised at the results. Next time, try mixing the sawdust with some smaller (chip size) pieces of wood, twigs and whatever is available. Or if you have access to some charcoal (you might have some in the pit now...dry it thoroughly) you can mix the charcoal with the sawdust. anything that will let air and combustion get into (and break up) the areas that are mostly sawdust. I have seen people use lengths of iron pipe as air intakes (placed in the pit vertically while placing the pots, and before lighting. You might incorporate some of those into your plans for a grate. Like they say...test, test, test, and good luck on your next firing! It sounds like you are on your way. Wayne Seidl

Stelios, I haven't been reading my newsgroups for a long time, so hope this might be of some help for next time, and hopefully you will see this.

I did a very successful pitfiring with some non-potter friends and every one came out "perfect". Though I'd warned them, some of them made very thick items, and others had little thin protrusions on their pieces. But none broke. I used raku clay (which can take heat shocks better than earthenware).

I bisque fired all the pieces to cone 04 first. My bonfire pit is about 12" deep, round, 4' diameter, earthen base, but surrounded with rocks. First layer was twigs, branches, kindling mixed with wads of newpaper, with pieces of newspaper sticking out from the edges all the way around the outside. Then larger branches (one inch diameter or so) Then a layer of sawdust.... very fine, from a portable sawmill.... oak and black walnut The pots were individually wrapped in newspaper, after festooning them with plants, copper sulfate (drain cleaner), salt, oxide powders, pennies (which I learned are NOT copper, and they melted into pewter-looking blobs). These were dispersed into the sawdust, covered with more sawdust, then in succession, twigs, branches, limbs, firewood sized pieces. We set fire to the newspaper sticking out from the bottom layer, and added more wood as the fire burned for about an hour. I then covered it with a piece of tin roofing that had holes punched into it with a shovel (every foot and half or so). This did not totally cover the whole firepit. Next day dug them out and they were wonderful..... mostly white, grey and black with not too much other color, though. Kira