EPK stands for “Edgar Plastic Kaolin” and is named after the company that has historically mined it from north-central Florida, the Edgar Plastic Kaolin Company, known today as Edgar Minerals Inc.

EPK is widely considered to be the best North American kaolin for use in suspending glazes because of its exceptional cleanliness, and it produces a smooth thixotropic slurry. It offers a high-quality white fired color, unusually good forming characteristics, and high green strength. EPK is whiter than other American kaolins because of its relatively low iron content and its low levels of titanium dioxide. 

About 15 million years ago, most of Florida as we know it today was submerged under a shallow sea. Parts of central Florida rose above the waters as islands, and what is now the Georgia-Florida border was actually an open channel of moving water known as the Gulf Trough. For a very long time, this channel prevented any kind of sediment running off the North American continent from settling on Florida’s detached and submerged platform, but a combination of lower sea levels and increased uplift from the Appalachian mountains to the north resulted in more and more sand and clay sediments entering the Gulf Trough. Eventually, these sediments filled the Gulf Trough and, along with other geophysical processes, connected Florida to the rest of North America. EPK is the buried result of that geologic story.

Before European colonization, this region was inhabited for thousands of years by a diverse collection of Indigenous communities that history remembers as the Timucua. These peoples probably had various names for themselves and one another and likely would not have referred to themselves as Timucua. They are now considered extinct.

In the 1880s, Charles Edgar began mining EPK after searching for the material all across north central Florida and finding it about 8 miles east of Hawthorne. A company town with Edgar’s name was established to support the clay mine’s workers and their families. Today, the mine’s main product is white sand, but EPK is still produced and distributed.

The clay and sand are mined simultaneously using high pressure streams of water that knock the material off the mine pit walls and into a pool in the middle. This slurry is pumped out of the pit, and vibrating screens separate out the sand from the clay. The clay is then pumped into a separate pool and a flocculant is added. Flocculation is when solid particles separate from the liquid they are suspended in to form loose aggregates or flakes, and a flocculant is a chemical agent added to a mixture to facilitate this process. The clay eventually dries and the flocculant is neutralized so that the finished clay product can be bagged and transported.

EPK comes from Edgar Mineral’s mine located at 651 Keuka Road, Hawthorne, Florida and is processed right across the street. From there, the clay travels to Rocky Mountain Clay in Denver. From Denver, the clay travels to Colorado State University for a total of 1,834 miles.