By Rose Stainthorpe

1600 feet underground, beneath layers of sandstone and shale, there is a network of roads, spanning miles and miles. Lights overhead illuminate the rasped walls and low ceilings of rooms and tunnels—there is a whole human world down here, of streets, bathrooms, maintenance shops, not to mention, hulking, colossal machines. One of them, broad and low-slung, begins approaching the wall ahead, its rotating teeth accelerating into a sharp whine until it is biting, shredding away at the rock. This is the world’s largest known deposit of trona, the material from which we derive soda ash. Almost 90 percent of soda ash in the United States comes from this place, underground, in the Green River Basin, Wyoming. 

Trona is, by far, Wyoming’s greatest global export—unimaginable quantities of Wyoming earth are hollowed out, shipped all over the world. The scale is staggering. Every minute and a half, a mine may hoist as much as 23 tons of material up to the surface.  In fact, this operation is so massive, the Federal Reserve Board uses soda ash production as a measure of the overall US economy. 

Trona use is old, its oldness revealed by its etymology. The English word ‘trona’ likely derives from either Swedish or Spanish (trona), but each of those, in turn, derive from Arabic (aṭrūn), the Arabic from Ancient Greek (nítron), and the Ancient Greek from Egyptian (nṯrj). Over 5000 years ago, Egyptians used natron (another source of soda ash) in glassmaking, as a soap, cleanser and antiseptic, and as a drying agent in mummification. Perhaps for these reasons, the Egyptian nṯrj is believed to have meant ‘divine’ or ‘sacred,’ since, to enter a temple, or to be mummified, meant cleansing or being treated with soda ash. 

Both the long history of soda ash, and the enormity of its mining operations and distribution networks today, attest to how much this material is embedded in our everyday lives. The vast majority of soda ash is used in glass manufacturing, be it in containers, fiberglass, or as a part of the construction or automotive industries. It is also used in air filtration, detergents, paper products, food products, and as a water softener. Ceramic studios, in other words, make up a truly infinitesimal portion of soda ash use. 

So, what is it? Sodium oxide, carbonate, crystal water. A coarse, opalescent grain. Soluble stuff, slippery and soapy in water. Of our materials, it is one of the few that is caustic—get it on your skin and it hurts. Even though, for our purposes, sodium is a powerful flux, we rarely use soda ash as a melter—unless to specific effect. Its solubility means that, when it is used in a glaze, it travels with water in and out of the pores of our bisqueware, creating less homogenous glaze chemistry. Instead, we frequently use soda ash as a deflocculant. It is also a common ingredient in frits, our prefabricated glass powders. And, of course, we use it in soda firings, in which we create a sodium vapor that interacts with the silica and alumina of our clays to form a glaze. 

Compared to another ceramic material mined nearby, Wyoming’s trona deposits are geologically young: a mere 50 million years to bentonite’s one hundred million. As the Western Interior Seaway began to recede and close, a large freshwater lake formed in Wyoming. Over time, runoff into the lake transported sodium, alkali and bicarbonate, creating what is, today, a trona bed of over one thousand square miles. Mining here is also relatively young—oil and gas exploration in 1938 revealed the presence of trona, and the first mine shaft was dug in 1946. It is a reminder of the interconnected web—often invisible—of resource extraction, as well as the political histories that enable it.