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PV Clay - 1 lb.
It is a feldspathic semi-abrasive mineral consisting of clay, mica, feldspar and silica (Moh hardness of 5). It is a product of the hydrothermal alteration of intrusive rhyolite and is mined from a substantial deposit in the Mojave Desert of California. In a ceramic casting slip or plastic clay body, PV Clay has the unique capability of promoting plasticity from the clay portion, fluxing action from the feldspar portion, and low shrinkage and stability from the non-plastic quartz portion. Its relatively high potash and soda content give P. V. Clay a lower PCE than most kaolins and ball clays (18 vs. 26-35), and thus was widely used in the ceramic industry as a low temperature flux for artware and tile bodies. Its formula is quite similar to Cornwall Stone. It has the unique ability to promote plasticity, fluxing and stability all from the same material. Its loss on ignition (approx 3% vs 10-15% for kaolins and ball clays) and its high silica content tend to impart low shrinkage, good density, and excellent hardness at low firing temperatures in the range 1900-2100F. It has an ideal combination of feldspathic silicates and kaolinites that permit low temperature firing in high talc bodies with exceptional resistance to glaze crazing and dunting during cooling. It promotes whiteness and imparts outstanding casting properties to ceramic casting bodies and floor & wall tile bodies. P.V. Clay is also used as a filler in rubber products, as a mild abrasive in polishes and cleansers, and as an extender for coatings, compounds, and other industrial products. It has good casting properties. It casts quickly, has good dry strength, a light color and long firing range and resists crazing very well. PV Clay was used in the "California Artware Body" as follows: California Talc 3 parts, PV Clay 1 part, Ball Clay Blend 2 parts. Vitreous white burning bodies can be made with high percentages of PV clay mixed with ball clay, silica and bentonite. Actually, when fired by itself it produces a pinkish color as it begins to vitrify around cone 6 and then progresses to a very white by cone 10. Firing properties are strongly influenced by the particle size (the finer the grade, the better vitrification achieved). P. V. clay can reach vitrification at cone 8, and is even used in glazes with success. A simple 50:50 mix of P. V. Clay and Gerstley Borate was used widely as a transparent glaze at cone 5-7. A mix of 80:20 PV and calcium carbonate produces a cone 10 transparent glaze. CaO 1.00, MgO 0.50, K2O 5.00, Na2O 0.90, TiO2 0.10, Al2O3 12.70, SiO2 76.50, Fe2O3 0.50. Source: Digital Fire.
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