Our trainer was Middie, an attractive young woman from Seattle. Had been with EcoHaus for a couple years and had a degree in interior design. Who'd think that she could sling mud with the best of them. In a couple hours she showed six customers about the product, how to mix it up and apply it to wall, drywall sheets in this case. Luckily she asked if anyone had a special color in mind and I piped up with Verde Valley (light green) which we planned to use in the kitchen area. So she mixed up a 50 pound bag in a jiffy, and off we went.
American clay is an entirely organic product. Its composed of about 75% marble dust (binder), clay, and fine sand or ground up shells. The clay and sand is mined in New Mexico, whereas the marble dust is probably imported from Italy (their sources and quarry locations are proprietary info, so I'm speculating on the basis of my geologic background). The company is family owned and operated out of Albuquerque, NM; been around for 10-15 years I think. Check out there website (http://www.americanclay.com/our-clay) for info and pretty pictures of their product in use.
We'll use two types of American Clay. You always start with Loma, a sandy clay plaster that is the base coat. Loma has a sandy feel when applied, so we'll use a second, finish coat of Porcelina, which is smoother and resembles Venetian plaster. The nice thing about American Clay is that it has no lime (cement) content, so cleaning up tools, clothes, and adjacent surfaces is easy. Also the material isn't caustic to your hands like cement. On the eco side of things, the clay plaster generates gobs of negative ions, which is a good thing for controlling dust and other particles in the air. Their web site goes on with feel-good technobabble like : "Negative ions are believed to produce biochemical reactions that increase levels of the mood chemical serotonin, helping to alleviate depression, relieve stress, and boost our daytime energy." If this is true, I'll be one happy camper surrounded by 600 square feet of the stuff.
Another nice attribute of the clay is that its a hygroscopic material, meaning it absorbs water. In the Pacific NW this is a good thing. To what extent it does this is tough say. I'd had an argument with the trainer in Santa Fe back in 2008. This gal, who later left the company, told us that the clay absorbed 300 times its weight in water. My god, how could that be. Common sense never entered her little mind. Clay materials have a bulk density of about 1.2 g/cc but could go higher (1.5 g/cc) if compressed (like American Clay). That means that a sugar cube (1 cm) size block of American Clay, enough to cover about one square inch (7 sq. cm) in a layer 1/16" thick (the typical applied thickness) weighs 1.5 g. So stick with me here. You spread a sugar-cube size wad (1.5 g) of American Clay on the wall and it covers a square inch. To do a square foot (144 sq. in), you'd need 144 x 1.5 g = 216 g of material. There are 2.2 pounds per kg, so 216 g is the equivalent of 0.46 pounds. This makes sense since American Clay says one 50# bag of Loma will cover about 200 sq. ft of wall. OK, now back to the weight of absorbed water.Your 216 g (0.46 lb) of clay covering that sq. ft of wall absorbs water with increasing humidity. If its foggy in the house, there is plenty of moisture to hydrate the clay. 300 x its weight in water means that one sq. ft of clay-covered wall absorbs 140 pounds of water, and that 1/16" thick layer must swell to about 18" in thickness. I have visions of a gooey mess. So what happened was that the trainer in Santa Fe mistakingly used x (times) rather than % (percent). Even after I pointed out the error and its common sense implications, she was reticent to admit the error and continued to claim the nearly miraculous qualities of the clay. Obviously she'd been much impressed with mud packs and mud baths. OK back to the walls and plastering.
After we apply the Loma clay, we'll come back and top coat it with the Porcelina clay. This has little to no sand in it so it comes out with a smooth surface, much like a babys butt (so to speak). When its dried to a leather hard surface, you can burnish it with a steel or plastic trowel which gives the surface a special patina. So it looks like the next week will be dedicated to priming the soon to be plastered walls and laying the tile on the master bath floor. Stay tuned.
