It seemed like a clever marketing gimmick. I was already successfully marketing hand-made Creek and Maya style ceramics. Why not go a step further and create authentic shell-tempered pottery for discriminating collectors? Both the Maya Commoners and the ancestors of the Creek Indians, after about 800 AD, made extensive use of crushed shells in fabricating utilitarian pottery.
Potters from several areas of the world independently discovered the benefits of adding crushed shells to raw clay. This additive cannot be applied to clay turned on a potter’s wheel because its sharp fragments would rip a potter’s hand to shreds. Shell tempering, however, makes hand-building of ceramic vessels much easier. The wet clay is much more rigid and not as likely to collapse. When the vessels are drying, they are far less likely to crack. Shell fragments function in clay like fiberglass does in concrete.
The big attraction for Maya and North American potters was the magic that crushed shells perform in a kiln. The hydrated calcite (CaCO3) melts into a form of glass at a much lower temperature than most of the other minerals in raw clay. Using heat to create glass is known as vitrification. A water-tight ceramic jar, tempered with crushed shells, would require perhaps ½ to ¾ the firewood needed to completely vitrify a conventionally tempered clay body. This was an important advantage in the Yucatan Peninsula where high population densities made wood scarce.
Within the interior of North America, fresh water mussels were the primary source of shells for shell-tempered pottery. They were a common food source. Some mussel species also produced pearls.
In order to make my shell-tempered pottery even more marketable, I decided to obtain my mussel shells from the site a very famous Native American town, where Hernando de Soto spent several weeks in the summer of 1540. The Spaniards recorded its name as Coça, which is pronounced Kō-shă. Its real name was phonetically almost the same; written as Kvse in Itsate Creek and Kaaxi in Itza Maya. Pronounced Kăw-shĭ in both languages, it meant “forested mountains” in Itza. English speakers generally write the word as Kusa or Coosa.
The ruins of Kusa are now under the Lower Reservoir of Carters Lake in northwest Georgia much of the year. Occasionally, the U.S. Army Corps of Engineers drops the Lower Reservoir level to work on the dam or kill several species of mussels are now thriving in the lake. When the water level is down, it is possible to obtain a grocery sack of deceased mussel shells in a few minutes. The shells are crushed by placing them in an old pillow and pounding them with a smooth river stone.
Cooking up a mess of mussel shells
The recipe for making and firing mussel shell-tempered pottery is not normally found in such places as Southern Living Magazine or Mother Earth News. Eventually, I found it in a blog post by an anthropology student at the University of Alabama. It stated that the crushed shells should be heated to about 550ᵒ F. till chalk white. This was necessary to drive out the chemical impurities and the water that was chemically combined with the calcium in the shells. That seemed simple enough.
I poured the crushed shells in a cast iron pot and placed it on a gas range. Steam quickly began rising from the shells. Hydrogen sulfide could be smelled as it was driven out. Then, as the shells turned white, there was an odd odor. I leaned over to sniff and saw stars. Fortunately, I had about three seconds to cut off the burner, before completely blacking out. I woke up on the kitchen floor about 30 minutes later. This obviously is an experiment that one should not try at home.
Eventually, a friend, who is a chemical engineer, figured out what had happened. Freshwater mussel shells contain chemical impurities that are not present in sea shells, particularly in their mother-of-pearl inner surface. When heated to over 500 degrees those chemicals react to create cyanide gas! Methinks that the young lady at the University of Alabama was either trying to make herself immortal by entering the Guinness Book of World Records through the most anthropology students killed at one time, or she really, really didn’t like her ex-boyfriend, the married professor. I could see her fluttering her lovely Alabama Belle eyes and demurely uttering, “Some more hot, crushed, Black Warrior River, mussel shells my dear?”
When you are hot, you’re not
My dream was to make a giant two gallon Maya tripod cooking pot to give to my tribe’s museum. While many anthropologists considered “the Mayas in Georgia thing” a bunch of bunk back then, we Creeks have always known that we had Maya heritage. It was also to be composed of symbolic materials. That’s a Native American thing. The inner walls of the cauldron were ball clay dug from near the site of Tama (visited by de Soto) on the Altamaha River in southeastern Georgia. The bright red slip on the surface came from high iron oxide clay that I dug near Etowah Mounds National Landmark. I burnished the pot to a mirror finish with a river pebble from the Chattahoochee River.
Instructions from the Alabama Belle with a death wish, said to fire the shell-tempered pottery to at least a cherry-red temperature and hold it there for two hours. What temperature is cherry red? All pottery turns “red hot” when being fired. I guessed she meant “earthenware temperature” and placed the appropriate temperature cones in my kiln.
The Maya tripod pot fired beautifully. There was not a flaw. The pot pinged like the finest porcelain. It glistened like a Corvette with candy-apple enamel on it. As soon as the pot cooled enough to pull out of the kiln, I photographed it, and sent an email to the tribe’s Mikko (Principal Chief) to brag about the gift that was coming his way.
The next afternoon, I happened to glance at the pot. Hairline cracks were forming that gave it the appearance of raku pottery. I didn’t understand how cracks could form 24 hours after coming out of the kiln, but the pattern made the pot look even more exotic.
While I was cooking breakfast the next morning the pot’s handles fell off. By noon the handles were two piles of ceramic pebbles. Throughout the day, I could hear pop, pop, pop, as more tiny shards exploded from the vessel. By noon of the third day after firing, the beautiful two gallon Maya tripod cooking pot was a pile of polychrome pebbles. It was an artistic disaster.
Further research in a book on Britannic-Roman shell-tempered pottery revealed the source of the disaster. Shell-tempered pottery can only be fired to the point when it just begins to glow red. If it is fired the translucent, orange-red glow of stoneware and porcelain ceramics, the calcite changes into an unstable chemical similar to Portland cement. After it cools, the unstable calcium compound will absorb moisture from the air and revert to hydrated lime. At this point, nothing bonds the clay particles together, so they disintegrate.
There were enough crushed, hydrated freshwater mussel shells to make a big batch of pottery, if I mixed them with limestone sand. The chemical reaction was the same for limestone as shells. The new pieces of pottery were fired to just the right temperature. They came out of the kiln perfectly and did not disintegrate afterward. However, making shell-tempered pottery was not worth the effort and risk. I decided to move on to the next phase of my career, which was watching archaeologists and bureaucrats go into convulsions when they realized that the world was not flat and the Mayas came to North America.
Sometimes at night, though, as I brush the icicles off my mustache and hear the coyotes howling up on Springer Mountain, I wonder, “How many Native American women went to the spirit world before they realized that you couldn’t sniff the pot of crushed, freshwater mussel shells while they are a-cooking on the hearth?”
Those readers who wish to ask Richard Thornton questions about architecture, urban planning or Native American history may email him at Native Question@aol.com .