FreeShip, Goldart Clay, Stoneware/Fireclay- (Prompt Rebate On Multi-Item FreeShip Orders!)

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We have two fireclays, Imco 800 and this listing's Goldart. Both are about 200 mesh, Goldart at 95% <74 microns. It increases refractoriness when used in clay body recipes. Clays that are resistant to deforming and melting at high temperatures earn the name of "fireclay". Probably almost anyone who works in ceramics has heard of Goldart. It has been a mainstay in the field for many years, from the 1960's and going back from there (I could not find when it was first mined). It comes from Cedar Heights Clay company who selectively mine it in southern Ohio. Goldart is a light buff color when fired at ^8, oxidation, and a cream color at ^2. It is vitreous stoneware at ^10. It is balanced enough to be used alone. It is an ingredient for scores of stoneware clay bodies on the internet currently and in books on ceramics going way before the internet existed.
Go to { https://glazy.org/materials/15258 } for tech info and a long list of clay recipes (earthenware to stoneware) containing Goldart. It is most often used in stoneware bodies, but it fits the definition of a fireclay, which is any clay that can be fired to a minimum temperature of 2,759 F (1,515 C), cone equivalent about ^19. It has a broad firing range which makes it valuable for stoneware clay bodies at cones 7 to 10 and it is versatile enough to be used alone (or with other refractories) as a high fired temperature (^10+) fireclay body for making kiln furniture and other refractory products. If fired at lower temps (^6 to ^10) it makes a wonderful base for many stoneware clays.
Digitalfire describes fireclay in general as "...a generic term that in the simplest terms refers to a refractory clay (one which can be fired to a high temperature without deforming or melting). Typically fireclays are plastic and have significant iron impurities. Light duty fireclays have a PCE [cone equvalent] of about 27 and super duty materials can melt as as high as cone 32.
The obvious use for fireclays is to make bricks and shapes for the structural elements in kilns and furnaces. These clay can be mixed with other materials to introduce air space in increase the insulating value of the product.
Fireclays are useful in many types of ceramics including brick, certain types of tile and sculpture and pottery clays. They impart plasticity and particle size distribution to the body and counter the early melting of any low temperature clays in the mix. For vitreous fireclay based bodies, considerable feldspar content is necessary.
Hundreds of different kinds of fireclays are available. However they are not normally interchangeable in body recipes since they vary drastically in plasticity, particle size, fired color, thermal expansion, and mineralogy."
Wikipedia { https://en.wikipedia.org/wiki/Fire_clay } says:
"Fire clay is a range of refractory clays used in the manufacture of ceramics, especially fire brick. The United States Environmental Protection Agency defines fire clay very generally as a "mineral aggregate composed of hydrous silicates of aluminium (Al2O3·2SiO2·2H2O) with or without free silica....
High-grade fire clays can withstand temperatures of 1,775 °C (3,227 °F), but to be referred to as a "fire clay" the material must withstand a minimum temperature of 1,515 °C (2,759 °F). Fire clays range from flint clays to plastic fire clays, but there are semi-flint and semi-plastic fire clays as well. Fire clays consist of natural argillaceous materials, mostly Kaolinite group clays, along with fine-grained micas and quartz, and may also contain organic matter and sulphur compounds.
Fire clay is resistant to high temperatures, having fusion points higher than 1,600 °C (2,910 °F); therefore it is suitable for lining furnaces, as fire brick, and for manufacture of utensils used in the metalworking industries, such as crucibles, saggars, retorts and glassware. Its stability during firing in the kiln means that it can be used to make complex items of pottery such as pipes and sanitary ware."