Sunday, March 2, 2008


Though the wind was calm when we awoke this morning, a high wind warning was posted and we didn't want to take any chances that our careful work would be undone. Rather than begin on the oven, we each worked on an experiment:

Our first step in oven building is to create a large sand dome, a hemisphere 16 inches high and 27 inches in diameter. The clay will be molded around the sand dome; when the clay dries and we remove the sand, we will have a domed void inside the clay oven. Odel's project was to determine the sand-to-water ratio for our sand form. Too much water and the sand will slump; too little water and the sand will collapse.

The result? He worked out the correct ratio, and built a little model which we visited from time to time throughout the day to see how quickly the sand dried. We're ready to tackle the real thing!

The oven will be heated with fire. It occured to us that many cultures use dried animal dung as fuel, and Rosanna has an unlimited supply here on the ranch! Rosanna's project was to see whether dried horse manure would really burn, and whether it could make a contribution to heating the oven.

This is a fire of both wood and manure. The manure burned well, but burned quickly, and we aren't sure whether it burned hot enough to be much help. The jury is still out on that one.

The manure had another potential contribution to make, though, and I worked on that. When the clay oven is completely dry, we intend to add a layer of "insulation" that will help both to retain heat and to protect the clay during the summer monsoons. The insulation is a mixture of clay and a dry, lightweight material. We used clay mixed with sawdust for the insulation below the oven floor, but I wanted to experiment with something potentially lighter.

A visit to the horse corral and I was all set. The clay/manure mixture was a great success. Once I had it mixed, Rosanna and I slapped some on the vertical side of our concrete block foundation to see whether it would stick and how long it would take to dry, and we are pleased with the preliminary results: light, stiff, and airy, excellent insulation.

By the time we were done with our experiments, the wind was starting to gust and we were glad we hadn't let our impatience to built the oven get the best of us. We're hoping tomorrow's weather will be calmer.


  1. I have never been quite sure where exactly the fire is. Is it inside the oven and then you bake after it's burned itself out? Or is it underneath the oven and you have to keep it going while you bake?

  2. The manure will also make the clay very adhesive and workable. Mix it the day before and let it sit just like you did before, you'll love it.
    Are you going to put some sort of "roof" over your oven? I didn't and was sorry but was moving anyway.