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Kaolinite, Calcined 5kg

SKU: NAP-510-15KLN5K
Kaolinite, Calcined 5kg
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Qty Price
 1   US$ 35.62 
 2   US$ 35.41 
 3   US$ 35.28 
 4-5   US$ 35.19 
 6-7   US$ 35.07 
 8-11   US$ 34.98 
 12+   US$ 34.85 
Price: US$ 35.62
US$ 35.62

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Product description


Kaolinite is a clay mineral with the chemical composition Al2Si2O5(OH)4. It is a layered silicate mineral, also known as china clay or kaolin.


The name is derived from Gaoling or Kao-Ling ("High Hill") in Jingdezhen, Jiangxi province, China. Kaolinite was first described as a mineral species in 1867 for an occurrence in the Jari River basin of Brazil.

Kaolinite is one of the most common minerals on earth. It is mined, as kaolin, in Brazil, France, United Kingdom, Germany, India, Australia, Korea , the People's Republic of China and the USA.

Kaolinite is a soft, earthy, usually white mineral, produced by the chemical weathering of aluminum silicate minerals like feldspar. In many parts of the world, it is colored pink-orange-red by iron oxide, giving it a distinct rust hue. Lighter concentrations of iron oxide yield white, yellow or light orange colors. Alternating layers of colored clay are sometimes found, as at Providence Canyon State Park in Georgia, USA.

Our white kaolin clay is from deposits in Texas, USA and is heat treated to remove some portion of its hydroxyl (OH) composition. Calcined kaolin is produced by heating ultrafine natural kaolinite to high temperatures in a kiln. The calcination process increases whiteness and hardness and alters the size and shape of the kaolin particles.

Kaolin-type clays undergo a series of transformations upon heating in air at atmospheric pressure. Dehydration begins at 550–600° C to produce disordered metakaolin, Al2Si2O7, but continuous hydroxyl loss (-OH) is observed up to 900° C. Due to disagreement concerning the nature of metakaolin, research has led to general consensus that metakaolin is not a simple mixture of amorphous silica (SiO2) and alumina (Al2O3), but rather a complex amorphous structure that retains some longer-range order (but not strictly crystalline) due to stacking of its hexagonal layers.

Between 100–200° C, clay minerals lose most of their adsorbed water. Between 500–800° C kaolinite becomes calcined by losing water through dehydroxilization. At this temperature range, kaolinite becomes metakaolin, with a two-dimensional order in crystal structure. In order to produce a pozzolan nearly complete dehydroxilization must be reached without overheating. This produces an amorphous, highly pozzolanic state, whereas overheating can cause sintering, to form the dead burnt, nonreactive refractory, called mullite.


Calcined kaolin clay is used as a functional extender in paint. For example, calcined kaolin clay has proven to be an excellent extender for titanium dioxide (white) pigment in paint. This is because kaolin clay is chemically inert, has a high covering power, gives desirable flow properties and reduces the amount of expensive pigments required. Its hardness also improves physical durability of the paint film and its burnish resistance.

Kaolin clay is also used in grounds, such as for painting and for gilding. The kaolin clay can be used in recipes calling for "pipe clay" and mixed with starch or flour to make a thick cream and applied to wood panel or canvas supports for painting. The ground dries quickly and several very thin layers applied one after another to form a ground typical of 19th century paintings.

Physical Properties
Median Particle Size (microns): 1.5
Hegman Grind: 5.5
Residue 325 Mesh (%) (ASTM C 325-81 or C 371-77): 0.05
Specific Gravity (ASTM C-329-75): 2.58
Bulk Density
Loose (lbs/cu ft): 23
Compacted (lbs/cu ft): 33
Mohs Hardness: 2.0-2.5
Oil Absorption (Gardner-Coleman): 60 g
pH Value (ASTM D 1208-78): 6.0
Brightness (Colorimeter): 89
Color: White
Refractive Index: 1.62
Moisture Content (max. %) (ASTM C 323-56 or C 234-82): 0.4
Loss on Ignition (%) (ASTM C 323-56): 0.3
Chemical Analysis
Chemical Formula: Al2Si2O5(OH)4
Silicon Dioxide (SiO2): 57.00%
Aluminum Oxide (Al2O3): 39.00%
Iron Oxide (Fe2O3): 1.00%
Titanium Dioxide (TiO2): 0.70%
Calcium Oxide (CaO) + Magnesium Oxide (MgO): 0.35%
Potassium Oxide (K2O) + Sodium Oxide (Na2O): 1.70%
Health and Safety

WARNING: The product contains crystalline silica-quartz, which can cause silicosis (an occupational lung disease) and lung cancer.


Average Particle Size: 1.5
Residue: 0.05
Hardness: 2.0-2.5
Oil Absorption: 60 g
pH: 6.0
Brightness (Colorimeter): 89
Color: White
Refractive Index: 1.62
Moisture: 0.4
Silicon Dioxide (SiO2): 57.00%
Aluminum Oxide: 39.00%
Fe2O3: 1.00%
Titanium Dioxide (TiO2): 0.70%
Calcium oxide: 0.35%
Potassium Oxide (K2O) + Sodium Oxide (Na2O): 1.70%

Natural Pigments

Natural Pigments is a limited liability company based in Willits, California. We manufacture and distribute rare and hard-to-find materials for fine artists and decorators. We specialize in supplying artists' materials that were used in historical painting since pre-historic times up to and including the nineteenth century.

We constantly search for materials and products of the finest quality so that we can bring them direct to you from the source. To do so, we travel the world to find materials specifically for use by professional artists and decorators. We obtain minerals from mines in Afghanistan, Chile, Russia, Ukraine and Uzbekistan, to name a few places, processing these into natural pigments. We purchase resins, gums and plants from India, Kenya and Malaysia to make natural varnishes and painting mediums.

Our mission is to provide the largest variety of natural pigments, paints and other professional artists' supplies, enabling us to bring you a selection that makes shopping for rare and hard-to-find art materials easy. Our objective is to promote the education and use of these materials among artists by providing detailed information for their employment in encaustic, fresco, oil, watercolor and tempera painting.
All Natural Pigments products

Product weight: 11.00 lbs

This product is shipped from our warehouse in Gretna, NE, USA.
This product is brand new and includes the manufacturer's warranty, so you can buy with confidence.
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Kaolinite, Calcined

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