Kaolin, ball clay

Clays are classified into six groups by the U.S. Bureau of Mines (1) kaolin, ball clay, fire clay, bentonite, fuller s earth, and common clay and shale. About half the toimage of clays produced in the United States is in the last category. In terms of monetary value, however, ka olin accounts for about two-thirds of the doUar volume. 

Ceramic processing occurs through some sequential activities, which starts with raw materials, proceeds through batch preparation and forming and concludes with firing. The sequence of steps is illustrated by Fig. 8.7. Ceramics are formed from raw materials used for traditional ceramics which are different from those used for advanced ceramics. For traditional ceramics raw materials consist of silica, clay, fluxes and are refractory materials. Silica is obtained either from massive quartz deposit or pure quartz sands. The quartz is washed and groimd. The most commonly used clay minerals are kaolin and talc. China clay is predominantly kaolin. Ball clays are finer particle size elays that contain... 

Fine-grained stonewares are different from natural stonewares because the grains of flux are no longer contained in the clay, but added in the form of feldspars. They are obtained from clay very poor in coloring, kaolin, ball clay and a mixture of orthoclase and albite. Colorings are sometimes added to the paste to develop a particular color in the mass of the product. Fine-grained stonewares are used as crockery, walls or floor tiles, antacid tiles and sanitary pipes. 

Sieve all the feldspar potash, ball clay, kaolin and silica powder by mesh, size 90 pm. 

Rappe C, Andersson R (2000) Concentrations of PCDDs in Ball Clay and Kaolin. Organohalogen Compds 46 9... 

Secondary clay has been transported from the site of the parent rock. As a result, this clay has fine particles and might be contaminated with iron, quartz, mica, and carbonate compounds. Ball clays are secondary clays. They are higher in iron content, more fusible, finer in particle size, and more plastic than kaolin clays. 

Certain properties of clays were known and exploited in ancient times in particular, clays were used for the fabrication of pottery, bricks and tiles. The chief constituent of china clay (or kaolin) is kaolinite, which is still used on a very large scale in the manufacture of paper and refractories. Ball clay, a line-grained form of kaolinite, contains some mica and quartz and is now favoured for crockery, porcelain and floor tiles. 

Ball clay — a sedimentary kaolinic clay that fires to a white colour, highly plastic, with very fine particle size. 

If the feldspar and quartz content is increased over that in hard porcelain, soft porcelain is obtained which is fired at 100 to 150°C lower temperatures. Highly plastic clay (ball clay) is added to obtain plastic and easy to work pastes, despite the lower kaolin content. Sanitary porcelains for the manufacture of bathroom articles are soft porcelain articles. 

Forming techniques used for clay-based ceramics require control of water content in the batch. Water content, in turn, affects the response of the clay during forming [27], As the water content of the batch increases, the yield point of the clay-water mixture, and thus the force required to form the desired shape, generally decreases [26], However, the relationship is complex and depends on the composition of the clay, its structure, additives to the batch, and other factors [14], One method for quantifying the behavior of clay-water pastes is to measure the plastic yield point as a function of water content [14], The water contents and maximum yield points in torsion are compared for several clays in Table 9. Kaolins and plastic fire clays require the least amount of water to develop their maximum plasticity, ball clays require an intermediate amount, and bentonite requires the most. 

China clay or kaolin, which is predominantly kaolinite. is particularly valuable because it is essentially free from iron impurities (and therefore colourless). World production in 1991 was 24.7M( (USA 39%, UK 13%. Colombia, Korea and USSR "7% each). In the USA over half of this vast tonnage is used for paper filling or paper coating and only 130000 tonnes was used for china, crockery, and earthenware, which is now usually made from ball clay, a particularly fine-grained, highly plastic material which is predominantly kaolinite together with clay-mica and quartz. Some 800000 tonnes of bail clay is used annually in the USA for white ware, table ware, wall and floor tiles, sanitary ware, and electrical porcelain. 

Within industry and commerce, terms other than the mineral classifications are common. Ball clay is a type of kaolin particularly suited to the manufacture of ceramics in 2001, 35% of the ball clay produced in the US was used for tile manufactoe, 22% for sanitary ware, 14% for pottery and various ceramics, 6% for refractory materials, 7% for other uses, and the remainder was exported. Kaolinite (which is white and soft) is of great importance in the paper industry for coatings and as a filler of the 8.1 Mt produced in the US in 2001, 36% was consumed in... 

Slaked lime is sometimes blended with the kaolin and ball clays used in the production of whiteware pottery. It helps to bind the materials and also increases the whiteness of the fired product [32.4]. 

The kaolin group includes kaolinite, nacrite, dickite and halloysite halloysite can also exist in a hydrated form having the formula Al2Si205(0H)4.2H20. Of all these, by far the most important is kaolinite, since it is the principal constituent of china clay, ball clay, fireclays, and many brick clays the other kaolin minerals are somewhat rare in Britain. 

A good deal of research needs to be done on the composition variations of pure minerals. As will be seen later, ball clays and fireclays contain a disordered kaolin mineral that departs considerably from the ideal formula, Al2Si205(0H)4. This obviously causes further inaccuracy in the calculation of rational analyses. 

The principal clay-mineral of ball clays is of the kaolin type, and closely resembles kaolinite but is less well-crystallized, and its empirical formula departs slightly from the ideal, approximating to ... 

With capillary casting, the demands placed on ball clay and kaolin producers are the same as with traditional bench casting. Additionally, faster casting and firmer casts are also required. The methods used to address these needs can be defined as similar to those of battery casting. Custom slurry products seem to offer the potential to improve performance in this area. 

The materials that fulfil all the conditions stated in this definition are kaolin, china clay, bentonite, bleaching earth, common clay, ball clay, fire clay, and refractory clay. The different aspects of the definition are explained below. 

Six types of clays are generally mined ball clay, bentonite, vermiculite, common clay and shale, fire clay. Fuller s earth, and kaolin. Most domestic clays are... 

American Hotel China. A vitreous type of pottery-ware. A typical body composition is (per cent) kaolin, 35 ball clay, 7 feldspar, 22 quartz, 35 whiting, 1. 

The most important clays in the pottery industry are the ball clays and china clays (kaolin). (See CLAY, BALL and KAOLIN.) The following paragraphs focus on special-purpose clays. 

The raw materials used for investigation of the porcelain production were ball clay horn Mukono, kaolin and feldspar from Mutaka and sand from Lido beadi on the shores of Lake Victoria in Entebbe, Uganda. The choice of these particular deposits was based on their satisfactory results from characterization studies on a number of available deposits. These deposits and material characteristics are described elsewhere. Representative samples were collected from the deposits and processed for use in this smdy. 

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