Fire clay

Fire clay is a range of refractory clays used in the man-ufacture of ceramics, especially fire brick. The UnitedStates Environmental Protection Agency defines fire clayvery generally as a “mineral aggregate composed of hy-drous silicates of aluminium (Al2O3.2SiO2.2H2O) withor without free silica.”[1]

1 Properties

High-grade fire clays can withstand temperatures of 1775°C (3227 °F), but to be referred to as a “fire clay” the ma-terial must withstand a minimum temperature of 1,515°C (2,759 °F).[2] Fire clays range from flint clays to plas-tic fire clays, but there are semi-flint and semi-plastic fireclays as well. Fire clays consist of natural argillaceousmaterials, mostly Kaolinite group clays, along with fine-grained micas and quartz, and may also contain organicmatter and sulphur compounds.Fire clay is resistant to high temperatures, having fusionpoints higher than 1,600 °C (2,910 °F), therefore it is suit-able for lining furnaces, as fire brick, and for manufactureof utensils used in the metalworking industries, such ascrucibles, saggars, retorts and glassware. Because of itsstability during firing in the kiln, it can be used to makecomplex items of pottery such as pipes and sanitary ware.

2 Chemical composition

The chemical composition typical for fire clays are 23-34% Al2O3, 50-60% SiO2 and 6-27% loss on ignitiontogether with various amounts of Fe2O3, CaO, MgO,K2O, Na2O and TiO2.[2] Chemical analyses from two19th century sources, shown in table below, are some-what lower in alumina[3][4] although amore contemporarysource quotes analyses that are closer.[5]

3 Extraction

Unlike conventional brick-making clay, some fire clays(especially flint clays) are mined at depth, found as aseatearth, the underclay associated with coal measures.

4 References[1] “Calciners and Dryers inMineral Industries” (Background

Information for Proposed Standards). U.S. Environmen-tal Protection Agency. 1985. pp. 3–48. EPA-450/3-85-025a{{inconsistent citations}}

[2] Minerals Zone, World Mineral Exchange. Retrieved2011-6-23.

[3] Thorpe, Sir Thomas Edward (1890). A Dictionary of Ap-plied Chemistry Volume I. Longmans Green & Company,London.

[4] King, William B. (1878). King’s Treatise on the Manufac-ture and Distribution of Coal Gas. self.

[5] Shackelford, James F (2008). Ceramic and glass materi-als: structure, properties and processing. Springer. p. 121.

1

2 5 TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES

5 Text and image sources, contributors, and licenses

5.1 Text• Fire clay Source: https://en.wikipedia.org/wiki/Fire_clay?oldid=680094313 Contributors: Alan Liefting, Leandros, Nabla, Kjkolb,Snowolf, HGB, Ground Zero, Bhny, CambridgeBayWeather, Shaddack, SmackBot, Snori, Fplay, O keyes, AndyAndyAndy, Luminaux,Wikid77, Magioladitis, STBot, J.delanoy, Theriac, Biscuittin, Toddst1, Excirial, Grapeguy, WikHead, Addbot, Yobot, Citation bot, Com-panicus, Shirik, Erik9bot, FrescoBot, Riventree, I dream of horses, Gaurav4490, ویکی ,علی Look2See1, Very trivial, ChrisGualtieri,PhantomTech and Anonymous: 27

5.2 Images

5.3 Content license• Creative Commons Attribution-Share Alike 3.0