How High Can It Go?

One question we are all very curious about is how hot can this mud oven get?

When working in the Craft of Fire, you start to develop a point of view on the history of the human being as the history of the production and management of ever-hotter fires. If you can get your fire hotter, you can produce new kinds of materials, and that brings with it certain (big) advantages:

 "When those who had forged iron came along and attacked the ones who had bronze weapons, the bronze would break. They came with iron and broke the bronze of the other guys. Run! It was ridiculous. Terrible. They had to run because their bronze would break. And so things moved from the Bronze age to the Iron age. The people of bronze had a superior civilization, with great productions, but they hadn't produced iron. And the other primitive types around where they lived hadn't melted bronze, they went straight and melted iron. And like that they defeated the ones with the superior civilization - because they had superior technology, not a superior civilization. But that's a historical anthropological discussion that could be called, 'On how the lesser can overcome the greater, in certain circumstances.' But the people of bronze shouldn't get cocky because they trounced the people of copper, too. And those of copper shouldn't get cocky either because they defeated the ones who hunted with sticks and bones... [And so on.]"  - Silo, the talk of 'The Stone', 2003

In our backyard we're a long way from bronze, or even copper. But with our more humble baked mud and clay and some wood, we thought we'd do a test to see how hot our oven gets.

We bought some pyrometric cones which melt at different temperatures and allow you to determine what temperature you've reached. The little red/gray coloured cones in the photo are (left to right), Cone 08, Cone 010, and Cone 014, whose respective bending points are 942°, 898°, and 807° C. These are usually used in kilns where the heat and rate of heating can be more carefully controlled, but we figured that, more or less, we would get some idea of how hot the oven environment was with this kind of spread, between 800° and 950° C. It was a guess on my part that that range would be feasible.

And since we were going to get this thing as hot as possible, I also put in a few clay pieces that needed firing. In the previous photo with the cones, you'll notice three little Venuses and a small pine cone, and in the photo immediately above, two of those hot neolithic mamas are getting nice and warm (the cones are behind them).

So we piled in the wood, spread it deeply throughout the oven, and kept the fire going for nearly 2 hours. At which point we realized that nothing at all had happened with the cones. In other words, we never even reached 800° C.

There they are, our stiff and toasty cones. Who knows, maybe the floor of the oven was 800°, or certain parts of the fire, but getting the entire ambient temperature up that high is no doubt a whole other matter...

(The consolation pizza, however, turned out very well.)

After dinner, we sifted through the coals in searching of the clay pieces.
And we found one casualty.

But two out of three goddesses ain't bad.
And I like how one fired black and the other came out white.

So it's back to the Pottery Supply store to get some even lower temperature cones and try the experiment again. And in the meantime, we'll also be making casts with our molds using the same mud-clay mix that we built the oven with, so we can fire them next time we do the test.
I made two quick casts, slapping the mud in without doing anything to improve its quality:

Stay tuned for the next oven temperature experiment, and to see if we can refine our mud and cast any half-decent objects with it...