Tag Archives | clay

336146CE-1CFA-47E5-86F9-67B59B669140

Jurassic coast

We recently visited the Dorset Jurassic coast, so named because it features layers of Jurassic limestone: 145 million year old Portland stone and Purbeck stone, as well as layers of Wealden clay, Greensand and Cretaceous chalk cliffs. Some of these layers contain fossil sea urchins and shells, and there is a even a fossil forest, with […]

Continue Reading
respirator mask

Glaze materials 2

Earthenware glazes are made mostly of frit, which is a kind of man-made feldspar. Borax, soda and other water soluble materials can be made insoluble by heating together with silica. The resulting glass is ground up and used together with clay and silica to make low temperature earthenware glazes. Frits are also used to lower the […]

Continue Reading
chalk and limesone, glaze material

Glaze materials

Stoneware and porcelain glazes are made up of at least four ingredients: silica, feldspar, whiting and clay.  This is what they look like in their raw mineral forms. Silica is ground flint or quartz, usually from sand or sandstone. These are large pieces of milky quartz from a vein in igneous rock. Silica has a high […]

Continue Reading
typesofclay

Clay structure

Clay is an amazing material. You can shape it and it holds its form, then you can fire it and it turns into stone. Under the microscope, clay is made up of tiny stacked hexagonal crystals, which are able to slide over each other when lubricated by water. The kaolinite image below is reproduced from […]

Continue Reading
Map of clay deposits in UK

Geology for potters

I am currently writing a book on Science for Potters for the American Ceramics Society. An extract on Geology for Potters has been published in Ceramics Monthly November 2015. Many potters use locally sourced clays and rocks in their clay bodies, slips and glazes. While researching for my book, I have become interested in geology […]

Continue Reading