Alternate Names: Isinglass, Muscovite, Biotite, Phlogopite
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Stable, virtually inert except to hydroflouric and concentrated sulfuric acid. Impervious to water and atmosphere. Unaffected by exposure to UV light, water or extended low and high temperatures. Free of asbestos and other non-asbestos fibrous materials. It is non-flammable, non-toxic and non-hazardous. Mica is invaluable in the electrical and electronics industries because of its unique combination of physical, chemical and thermal properties, low power loss factor, dielectric constant and dielectric strength. Also used in insulation, paint, metalurgical, and polymers.
Mica flake is used in low fire clay bodies to add a sparkle effect. Typical grades are too fine, drilling mud grades are more suitable. Typically its use is limited to below cone 02 since the particles can melt above that (test your material to find out). Water washed micas are superior for this purpose. While this technique has been employed by various potters it is actually an old process. For more information about its history, see the book "All That Glitters" (available at www.axner.com) and micaclay.com.
Data sheets for various mica products quote a wide range of decomposition and melting temperatures (as high as 1800C for melting and 1500C for decomposition). A typical melting point of muscovite is around 1250-1300C. However there are many different kinds of mica. Thus it is impossible to give a formula and difficult to give a general chemistry (micas are never employed in ceramics for their chemistry anyway, the mineralogy of the material is what is important).
Clay-making mineral of the group mica (illite, glauconite, celadonite, etc.), a hydrous aluminum disilicate normally made up of Al, Si, K, Mg, Fe and Li plus traces of other metals. Can be used as a sort of catch-all mixture of recipe ingredients much as ash can be used, though not for the same or even similar composition, nor does mica absorb water as does an ash; and especially for increasing plasticity. Particularly when added to glaze slurries, a flocculant can hold the mica in suspension
for better mixing.
see aventurine, muscovite and schist
Muscovite Star Mica
An example of how a small addition of mica affects the fired appearance of a terra cotta clay. The effect is still working at cone 03 (left) but is more commonly employed at cone 06 (right). Notice that it is still visible even under the glaze. This body is popular on the west coast, it was designed by D'Arcy Margesson. Standard grades of mica are too fine for the effect, this is likely Custer LCM Drilling Mud Mica.
Out Bound Links
A mica mineral.
A form of mica often found as micro-flakes in processed raw clays. It can often be found in the mineralogical analysis of materials.
In Bound Links
In contrast to man-made materials (like frits), ceramic minerals have a highly ordered atomic structure and a specific range of crystalline manifestations. By taking the characteristics of these into account technicians can rationalize the application of glaze chemistry when recipes are mixtures of ...