FreeShip- Kyanite Grog, Super Refractory, 48 Mesh - (Prompt rebate on orders with 3 or more FreeShip items!)

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Not all quantities are pictured.

We also carry this in a 35 and a 100 mesh, see the above link.
Grog is a hard, calcined clay or clay-like material which is then ground to a specific mesh size. Grogs are made of many different clays and minerals. Grogs are added to clay bodies to improve specific properties of the clay.
Kyanite is a unique refractory grog material. All grogs are refractory to a degree, but this one is special. The particle shape is needle-like. It is also a very high temperature refractory. In coarser meshes it makes an excellent grog for high fire clay bodies. It's a brown with reddish undertones. It is often used in high refractory applications. It's a beautiful looking material and would interesting added as a filler to clear resins and coatings
Digital Fire, the ceramics database says { https://digitalfire.com/4sight/material/kyanite_951.html } :
"Kyanite is a super-duty refractory material with very high resistance to thermal shock. It is widely employed in insulating brick, kiln furniture, refractory shapes, etc. and in body formulations used in porcelain, tile bodies, and casting mixes. The material reduces fired shrinkage, increases mechanical strength and thermal shock resistance and allows products to be made with thinner walls, better resistance to dunting, deformation and chipping. Kyanite's long jagged particles tend to form an interlocking no-shrink crystal matrix (like a felt) in bodies fired to low heat (potters use it up to 30% in raku bodies). Because of the particle shape, considerable amounts of kyanite can be added to bodies without adversely affecting their plasticity. For example, 10-15% 48 mesh kyanite can actually increase the plastic strength of smooth throwing bodies, making it possible to throw larger sized vessels. The above mentioned benefits will accrue and, in addition, drying properties will be better. However, the dry and fired surface will be a little rougher [with the large mesh kyanite].
Its large grain sizes make an excellent high temperature grog. It is volume stable and has excellent hot load strength. Because of its expansion characteristics it makes an excellent crack filler.
Kyanite is available in varying grain sizes down to 325 mesh and in calcined-to-mullite form. The decomposed mullite form is volume-stable with temperature increase, while the raw form of kyanite displays definite expansion during heat-up. Depending on grain size, this phenomenon permits the use of kyanite in clay formulations to counteract the shrinkage of the clay body during firing (see also Spodumene). Kyanite has proven invaluable in cements, ramming mixes, and mortars for this purpose."

Wikipedia has a short article on Kyanite { https://en.wikipedia.org/wiki/Kyanite } :
"Kyanite is typically a blue aluminosilicate mineral....At temperatures above 1100 °C kyanite decomposes into mullite and vitreous silica...This transformation results in an expansion [of the fired material]....Kyanite is used primarily in refractory and ceramic products, including porcelain plumbing and dishware. It is also used in electronics, electrical insulators and abrasives."

Wikipedia also has a general article on grogs. They treat their description as if any other grog is not a grog.
{ https://en.wikipedia.org/wiki/Grog_(clay) } :
"Grog, also known as firesand and chamotte, is a raw material for making ceramics. It has a high percentage of silica and alumina.
It is normally available as a powder or chippings, and is an important ingredient in Coade stone (an ancient type of ceramic stoneware)...
Grog is composed of 40% minimum alumina, 30% minimum silica, 4% maximum iron(III) oxide, up to 2% calcium oxide and magnesium oxide....
Grog is used in pottery and sculpture to add a gritty, rustic texture called "tooth"; it reduces shrinkage and aids even drying. This prevents defects such as cracking, crows feet patterning, and lamination. The coarse particles open the green clay body to allow gases to escape. Grog adds structural strength to hand-built and thrown pottery during shaping, although it can diminish fired strength.
The finer the particles, the closer the clay bond, and the denser and stronger the fired product. The strength in the dry state increases with grog down as fine as that passing the 100-mesh sieve, but decreases with material passing the 200-mesh sieve."-

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Aug 28, 2020

Christopher Martinez