Monday, May 14, 2007

Wattle and Daub

We have been finding many chunks of burned clay in the three most recent house excavations (units 315, 316, and 317). These are burned daub, sometimes called “bajareque.” They are evidence of the use of wattle-and-daub construction in the houses at Calixtlahuaca. This is somewhat of a surprise, both in terms of the presence of this type of house in the Toluca Valley

and in the nature of the construction methods. Wattle and daub is a form of house construction that was used in virtually all parts of the world in ancient times, and in traditional ethnographic houses in tropical areas today. A frame is built of sticks or cane; this is the wattle. Then mud (daub) is applied over the frame. The mud dries and fills in the spaces between the wattle. When a wattle-and-daub house burns down, the daub (sun-dried clayey mud) is fired like any other ceramic material, and becomes hard and almost indestructible.

The photo shows some of the pieces of burned daub from unit 316. The first odd thing is that this kind of construction was used at all in the Toluca Valley. Most Aztec houses in central Mexico were built using methods and materials that are still found today in traditional peasant houses in the same region. The stone foundation walls and adobe brick construction of Aztec houses I’ve excavated in Morelos match precisely the foundations and walls of modern peasant housing in the area. We found small amounts of burned daub at these sites, and wattle-and-daub construction is still used today in Morelos for traditional kitchens and occasionally for houses. Aztec houses in the Valley of Mexico are also quite similar to modern peasant houses in the area.

Wattle-and-daub is rarely or never used in peasant houses today in the vicinity of Toluca and Calixtlahuaca; in fact I can not recall seeing this technique at all. Modern traditional houses are built of adobe bricks. I had figured that the climate was too cold and rainy around here. But the hundreds of pieces of burned daub shows that this conclusion was incorrect.

The second unusual thing about our burned daub is its form. The burned daub I have seen from Morelos and from other parts of highland Mexico (e.g., Oaxaca) shows the impressions of numerous closely-spaced thin sticks or canes. All pieces show one or more cane impressions. Although some of our daub looks like this, much of it is different. Some pieces show only a single stick impression (photo, upper right), and some show none at all. Many pieces have a very well-smoothed surface, and some pieces have several smoothed surfaces. At first we thought that the piece in the lower right of the photo was a fired brick (a technique not used prior to the Spanish conquest). But washing and close inspection showed that this is clearly burned daub, not brick. Overall, our daub more closely resembles construction methods in which the wattle provides a frame for the daub, but many pieces of daub were not in contact with the wood. The sketch shows a traditional wattle-and-daub house from Italy (modified after: Shaffer, Gary D., 1993, An Archaeomagnetic Study of a Wattle and Daub Building Collapse. Journal of Field Archaeology 20:59-75. This kind of construction was common in European Neolithic houses.

In reading about the archaeology and ethnoarchaeology of wattle-and-daub houses, I am struck by the fact that accidental fires are almost never sufficient to fully fire the daub. When archaeologists find extensive burned daub at a site, it is almost certain that the houses were deliberately burned down; additional fuel typically has to be added to the fire. Perhaps significantly, two or three of our excavations with abundant burned daub also have extensive areas of burned earth and charcoal. Who burned these houses and why? We are still looking for answers to these and other questions.