This is from the "Pit" section of the marvelous book Alternative Kilns and Firing Techniques, by James Watkins and Paul Wandless.
Pit firing is simple and very, very old, and most cultures have some variant of it. In Mexico burnished work is sort of sandwiched between layers of wood above the ground, then lit like a bonfire. In parts of Africa the pots are stacked aboveground and covered with brush and grass and any other dry plant material, and that is then burned. Firing in the ground means the earth acts as an insulator, so the fire can burn hotter. One effect of this is that colors become more pronounced, not just black and gray.
There's some minimal history; now on to the logistics. Watkins and Wandless (W&W) say to dig a hole as deep as it is wide, say 24", and fill the bottom with a three-inch layer of sawdust (more on that soon), small twigs, and newspaper. I have an abundance of twigs and my boyfriend is kindly saving his newspapers for me as I do not get the newspaper.
In an electric kiln the wok is placed upright, on shelves, but here I'll be doing something called tumble stacking, which means using no shelves and packing the pieces in there so they look haphazardly placed - but are really very carefully placed indeed, with sturdier/larger ones on the bottom, and as little of their area touching each other or the walls of the pit as possible. (Areas cut off from the smoke will not get the colorful effects as distinctively.)
Then you pack the pit around the pieces, with layers of straw, sawdust, and newspaper, according to W&W. I'm going to use kindling instead of straw, and I don't know how much sawdust I'll have, but I'll make sure that I get a lot of small combustibles of one kind or another. This packing will also help ensure that they stay stacked as they are, and that the wood which will be placed on top doesn't fall and crack them. (I hope, I hope, I hope.)
You then stack some of the larger wood pieces on top of the pile, which should be at ground level. Soak them with lighter fluid (I don't know what's in that, I don't have anything specifically designated as such, I'm going to use gasoline) and toss in a match. According to W&W the fire should burn for about an hour, but stay hot for many hours after that. It will reach temperatures between 1000 and 1350 F.
It is very very VERY important not to unpack the pit too soon, for safety and more importantly because the sudden temperature differential will cause the pieces to crack. I have witnessed this with electric kilns. So I must overcome my curiosity and let the pit cool overnight at least before seeing what I have wrought.
Pit firing is simple and very, very old, and most cultures have some variant of it. In Mexico burnished work is sort of sandwiched between layers of wood above the ground, then lit like a bonfire. In parts of Africa the pots are stacked aboveground and covered with brush and grass and any other dry plant material, and that is then burned. Firing in the ground means the earth acts as an insulator, so the fire can burn hotter. One effect of this is that colors become more pronounced, not just black and gray.
There's some minimal history; now on to the logistics. Watkins and Wandless (W&W) say to dig a hole as deep as it is wide, say 24", and fill the bottom with a three-inch layer of sawdust (more on that soon), small twigs, and newspaper. I have an abundance of twigs and my boyfriend is kindly saving his newspapers for me as I do not get the newspaper.
In an electric kiln the wok is placed upright, on shelves, but here I'll be doing something called tumble stacking, which means using no shelves and packing the pieces in there so they look haphazardly placed - but are really very carefully placed indeed, with sturdier/larger ones on the bottom, and as little of their area touching each other or the walls of the pit as possible. (Areas cut off from the smoke will not get the colorful effects as distinctively.)
Then you pack the pit around the pieces, with layers of straw, sawdust, and newspaper, according to W&W. I'm going to use kindling instead of straw, and I don't know how much sawdust I'll have, but I'll make sure that I get a lot of small combustibles of one kind or another. This packing will also help ensure that they stay stacked as they are, and that the wood which will be placed on top doesn't fall and crack them. (I hope, I hope, I hope.)
You then stack some of the larger wood pieces on top of the pile, which should be at ground level. Soak them with lighter fluid (I don't know what's in that, I don't have anything specifically designated as such, I'm going to use gasoline) and toss in a match. According to W&W the fire should burn for about an hour, but stay hot for many hours after that. It will reach temperatures between 1000 and 1350 F.
It is very very VERY important not to unpack the pit too soon, for safety and more importantly because the sudden temperature differential will cause the pieces to crack. I have witnessed this with electric kilns. So I must overcome my curiosity and let the pit cool overnight at least before seeing what I have wrought.
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