By Tara Whelan
The weekend of June 22-23, 2012, some earth TEACHINGS hosted a natural building workshop on Earth Plasters & Natural Finishes. Architect and Director of soma earth, Ingrid Cryns led the workshop. Ingrid has much experience in building with straw, earth and mixing her own plasters. Our task for the weekend was to mix and apply a finish coat to the exterior of a straw bale and straw clay building while also learning the recipes and applications for other layers of plasters and natural finishes.
Starting off with a tour of the straw bale and straw clay building that we would be applying the plasters to, we saw different techniques of finishing and smoothness on the interior and the base layer of the exterior. Our first exercise was hand, or rather foot mixing a batch of base layer plaster to apply directly to some straw bales. Everyone jumped right in and mixed it up with our feet, trying to feel for the right consistency of water, clay and sand, we also threw in some chopped straw and manure for adhesives (and fun). For some, mixing the manure was a little challenging! One enterprising participant used surgical gloves on his feet to protect them!
After experimenting with our feet, we moved on to machinery so that we could learn how to mix the earth plaster in a mass production kind of system. To our surprise, we discovered that preparation work before we can get mixing is a big part of making these earth plasters. First we learned how to add a light clay slip to the straw bale walls in advance so that the plasters adhere better. Then the most intense major task is spending the time to properly and carefully sift the stone aggregates out of the clay and sand. We had large mesh screens to push all the dirt through to ensure there are not any large pebbles otherwise they will leave streaks and bumps or holes on the wall later.
We learned an interesting technique as to how to determine if you have any clay in your soil sample. You take a small ball and spit on it to add moisture, keep massaging it with your hand until you can roll it into a long coil. If you can bend the coil into a perfect circle without getting any cracks, then you have enough clay to work with!
Eventually, after sifting enough clay and sand we finally had enough to mix it up! I don’t think we can share our secret ingredient (TLC!), but the rest is a typical ratio of slowly adding water to – 1 part clay, to 3 parts sand, with additional binding agents – flour paste, manure and bull rushes in this case for the finish coat, or finely chopped straw for a base coat.
So, finally it was time to apply the plaster mix to the building! We had a small group of people but we were ready to get messy! Although, to our surprise, it was much more difficult and tiring than expected! Using our plaster hawks and trowels we were shown the correct (and easiest) way to apply the plaster to leave a clean finish and larger biceps!
The following day we had some new participants and we were asked to recap the processes from the previous day (with Ingrid assisting in reminding what was important to have learned). A great experiment that we did was adding different proportions of sand/clay/water to several jars to see how the particles settled over a day. The jar test showed that the clay that we were using was quite sandy. For the rest of the workshop, we learned how to mix the batches and test the consistency ourselves. A few mistakes were made in proportions, but by adding just little bits of sand or clay or binder in proportion at a time, you can always recover to create the perfect mixture.
At the end of the day, we all got to relax with some snacks while Ingrid presented a slideshow discussing other ways earth is used in construction and finishes (including earth bag building and earth floors which she plans on building soon). We also discussed other natural paint finishing options for healthy indoor & outdoor environments and where to get them in the area.
Overall this workshop was very productive since we got to do everything ourselves so that we remember it. We also met some fun people, including a fabulous woman who is going to be building her own straw bale building barn/workshop this year!