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Grog (clay)

 

 
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Grog (clay)
 
 
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Grog, also known as firesand and chamotte, is a ceramic
Ceramic

File:Bridge from dental porcelain.jpgFile:Qing vase p1070256.jpgA ceramic is an inorganic, nonmetal solid prepared by the action of heat and subsequent cooling....
 raw material. It has high percentage of silica and alumina. It can be produced by firing selected fire clay
Fire clay

Fire clay is a specific kind of clay used in the manufacture of ceramics, especially fire brick. The fire attribution is given for its refractory characteristics....
s to high temperature before grinding and screening to specific particle sizes. It can also be produced from pitchers
Pitchers (ceramic material)

Pitchers are pottery that has been broken in the course of manufacture. Biscuit pitchers are crushed, ground and re-used, either as a low-percentage addition to the virgin raw materials on the same factory or elsewhere....
. The particle size distribution
Particle size distribution

The particle size distribution of a powder, or granular material, or particles dispersed in fluid, is a list of values or a mathematical function that defines the relative amounts of particles present, sorted according to size....
 is generally coarser in size than the other raw materials used to prepare clay bodies. It tends to be porous and have low density.






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Grog, also known as firesand and chamotte, is a ceramic
Ceramic

File:Bridge from dental porcelain.jpgFile:Qing vase p1070256.jpgA ceramic is an inorganic, nonmetal solid prepared by the action of heat and subsequent cooling....
 raw material. It has high percentage of silica and alumina. It can be produced by firing selected fire clay
Fire clay

Fire clay is a specific kind of clay used in the manufacture of ceramics, especially fire brick. The fire attribution is given for its refractory characteristics....
s to high temperature before grinding and screening to specific particle sizes. It can also be produced from pitchers
Pitchers (ceramic material)

Pitchers are pottery that has been broken in the course of manufacture. Biscuit pitchers are crushed, ground and re-used, either as a low-percentage addition to the virgin raw materials on the same factory or elsewhere....
. The particle size distribution
Particle size distribution

The particle size distribution of a powder, or granular material, or particles dispersed in fluid, is a list of values or a mathematical function that defines the relative amounts of particles present, sorted according to size....
 is generally coarser in size than the other raw materials used to prepare clay bodies. It tends to be porous and have low density. It is available as a powder, mortar
Mortar (masonry)

Mortar is a workable paste formed by mixture of cement, water and fine aggregate masonry to bind construction blocks together and fill the gaps between them....
, or in the form of fire brick
Fire brick

A fire brick, firebrick, or refractory brick is a block of Refraction ceramic material used in lining furnaces, kilns, firebox , and fireplaces....
s.

Properties

Grog is composed of: 40% minimum alumina (Al2O3), 30% minimum silica (SiO2), 4% maximum Iron(III) oxide
Iron(III) oxide

Iron oxide?also known as ferric oxide, Hematite, red iron oxide, synthetic maghemite, colcothar, or simply rust?is one of the several oxide Chemical compounds of iron, and has Paramagnetism properties....
 (Fe2)3), and 2% maximum of calcium oxide
Calcium oxide

Calcium oxide , commonly known as burnt lime, Lime or quicklime, is a widely used chemical compound. It is a white, Caustic and alkaline crystalline solid at room temperature....
 (CaO) and magnesium oxide
Magnesium oxide

Magnesium oxide, or magnesia, is a white solid mineral that occurs naturally as periclase and is a source of magnesium . It has an empirical formula of ....
 (MgO) combined.

Its melting point is approximately . Its water absorption
Water absorption

Water absorption is a phenomenon in the transmission of electromagnetic radiation through a medium containing water molecules. Water molecules are excited by radiation at certain wavelengths and tend to selectively Absorbance portions of the spectrum while allowing the balance of the spectrum to be Transmittance with minimal effect....
 is 7% maximum. Its thermal expansion coefficient is 5.2 mm/m and thermal conductivity
Thermal conductivity

In physics, thermal conductivity, , is the List of materials properties of a material that indicates its ability to conduct heat. It appears primarily in Heat conduction#Fourier's law for heat conduction....
 is 6–9.5 W/(m·K). It is also not easily wetted by steel
Steel

Steel is an alloy consisting mostly of iron, with a carbon content between 0.2% and 2.14% by weight , depending on grade. Carbon is the most cost-effective alloying material for iron, but various other alloying elements are used such as manganese, chromium, vanadium, and tungsten....
.

Applications

Grog is used in pottery
Pottery

Pottery is the ceramic ware made by potters. Major types of pottery include earthenware, stoneware, and porcelain. The places where such wares are made are called potteries....
 and sculpture
Sculpture

Sculpture is Three-dimensional space artwork created by shaping or combining hard and or plastic material, sound, and or text and or light, commonly Stone sculpture , metal, glass, or wood....
 to add a gritty, rustic texture called "tooth"; it also reduces shrinkage and aids even drying. This prevents defects such as cracking, crow feet patterning, and lamination. The coarse particles open the green clay body to allow gases to escape. It also adds structural strength to hand-built and thrown pottery during shaping although it can diminish fired strength.

Other uses for grog is processing ZnO Metal Oxide Varistor
Varistor

A varistor is an electronic component with a significant non-Ohm current?voltage characteristic. The name is a portmanteau of resistor#Variable resistors....
 (MOV). It is put at the base of the "blocks" on the topside of the bottom of a refractory sagger to keep the blocks from sticking to the sagger. This is because ZnO MOV has a polymer binder that upon drying acts as a glue. The grog at the base prevents gluing and acts as a vent for carbon gases while drying and sintering. The grog is a gritty form of ZnO to prevent contamination.

Bibliography

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