Plaster with teeth

17 Nov

Serendipity sometimes proves to be a pleasant surprise. One day while we were El Punto doing other things, we took a break and tried making a sample of plaster from resources within our own tract of land. Ed had some sifted clay in a bucket. We also had a bucket of screened sand. The barrel under the gutter for the ramada roof was full of rain water. Then we strayed from convention: we shredded several dried leaves of lechuguilla, a prominent succulent in the Chihuahuan desert.

Bowl of clay, sand and water, lechuguilla fibers, dried leaves below.

Because of last year’s drought, many plants  throughout the northern Chihuahuan desert suffered a high mortality. Frankly, the desert in Big Bend region looked parched. Prickly pear cactus and lechuguilla were the most hard-hit and many have still not recovered with this year’s high rainfall. Thus an abundance of dead lechuguilla leaves are all around our place. Knowing that indigenous peoples used to pull apart the fibers of of this plant to make rope and sandals, we spent an hour pulling fibers to make a small pile to add to our plaster mix. In place of straw, which is conventionally used in cob and plaster mixes, we experimented with using what we had ready access to.

When adding the fibers to the wet mix it could not really be differentiated from thin straw. We proceeded to hard trowel the mix with fibers onto the exterior of a few of adobe blocks that form the west wall of the ramada. Even the wooden trowel was made at home; Ed sourced a few wood board scraps and fashioned a nice handle. Pushing hard on the plaster to work it into the adobe surface and joints, we stood back and hoped for the best.

Plaster after 12 hours of application.

The next day  I checked our plaster experiment and photographed it before leaving. Considering that it was applied in the heat of the day and sunshine, the cracks were few and not deep. The lechuguilla fibers seemed to impart a subtle black stain on the plaster surface, which Ed wasn’t pleased with. But I reminded him that time will tell if the stains are permanent.

A month later I checked our plaster experiment. Completely dried, the dark streaks had disappeared and the cracks remained superficial. Nor could I pull any of it from the surface of the blocks! It remains firmly attached. I posit that if the raw plaster had been applied under more favorable weather – i.e. cooler temps and not in the direct sunlight – cracking would have been greatly reduced.

As for mass production of this mix, using dried lechuguilla would probably be nearly if not completely prohibitive. We pulled the fibers and ripped them from the leaves by hand. Straw used in plaster is usually chopped to fine fibers by running through a hammer mill twice. Considering the strength and tightness of lechuguilla leaves, it would take a large and sturdy hammer mill to reduce the leaves to individual short fibers. We will probably stick with straw for our plastering jobs in the future.

Lechuguilla plant (Agave lechuguilla). Note the dead and dried leaves at the base.

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