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Ocean Sediment Glazes
by Joan Lederman

Communities of organisms, dead and alive, have settled in layers on the ocean floor and are sometimes taken by researchers as core samples. Occasionally, I get their excess. I learned that most samples melt into a glaze at cone 10 and 11.

They each have a character of their own. While the glazes that humans have concocted are often exquisite... they have a different voice. They are more contrived from nature than they are released by nature. I achieve my results by thinning the mud-like ocean sediments with fresh water and applying them like any glaze. Many make branching patterns like river deltas, our brains, and some potters say, like ash glazes. They appear to flow downward while crystallizing upward. Some look waxy and thick, and some look glassy and liquid.

How might this be useful to other potters? A potter with persisting interest could find out which institutions send ships out to collect cores. Possibly a Google search on coring would offer names of all the archives in the world and approaching one by one might turn up some samples.

I began this process when a sample arrived at my door and the kiln was on, so I stuffed some into a spy hole. It melted. The next test was a bisque firing and in a third test sediment was thinned with water and applied to clay. That’s when I discovered foraminifera - small calcium carbonate shells which science uses to date materials. In nine years of using these materials, I observed that sediments with foraminifera usually make branching patterns. So far, no sediments from the Pacific Ocean have made branching patterns.

I’ve used materials from various locations, including the Arabian Sea, the Dead Sea, the Red Sea, the Mediterranean, the Bering Straits and the Black Sea, the Indian Ocean, Pacific Ocean, Southern Ocean and the Atlantic Ocean, as well as materials from hydrothermal vents and crust slurry from the mid-Atlantic Ridge crust. I’ve also learned that magma within the Earth, which takes many forms after volcanic eruptions, and land samples in Iceland, are similar to those in Hawaii. This should come as no surprise, since we all do float on the same core.


I live in Woods Hole, Massachusetts, USA. It is a deep-water port and home to many research institutions, including the Woods Hole Oceanographic Institution, which is how I happened to receive these materials. I mark the source locations on the pots, so the stories are accessible to people. Many photos of pieces are available as food for the eyes on my website The Soft Earth.

If anyone out there would like to continue this type of work, or wants to undertake an applied interdisciplinary program at a university, I would love to see more people doing it... and will help by sharing my knowledge. I am interested in hearing from you, if further discoveries result from someone having read about my work, in partnership with the Great Mother Earth. She is a good teacher for me. Joan may be contacted by email: .


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