Body clays

Scrubbing andDesliming. Sylvinite ores in North America contain 1—6 wt % water-insoluble clays. A significant portion of these clays is less than 0.002 mm in diameter. If not removed or controUed in some manner, clay bodies that are dispersed in the flotation solution, ie, brine saturated with KCl and NaCl, absorb the amine coUector, which is added to effect flotation separation, and the coUector is rendered ineffective. Clay is the most troublesome impurity encountered in the processing of sylvinite ore. 

Ceramics. In ceramics, talc is widely used in wall tile and hobbyware bodies, in electrical porcelains, and in cordierite formulations. Wall tile and hobbyware ate talc—clay bodies that ate pressed and fast-fired to a high porosity (bisque) and then glazed and tefired to produce the final product. Talc containing tremolite and carbonate is preferred to ensure good porosity. 

Examples of plasticizers include adsorbed water and ethylene glycol for vinyl binders, stearic acid and oleic acid for wax binders, glycerine and ethylene glycol for clay bodies, and molten oils and waxes for thermoplastic polymers used in injection mol ding. 

With the aid of color illustrations Harrell and Russell (I) have shown some of the color changes that can occur in several clay bodies when the furnace atmosphere is varied from oxidizing to reducing and when its moisture content is controlled. Brownell (2) has summarized the roles of several factors influencing the development of scummed surfaces on brick and other structural clay products. Matson (3) has discussed the relationship of the firing temperatures of ancient Near Eastern pottery and the colors developed together with other physical properties of the wares. 

The surfaces of ancient pottery were often decorated with a ferruginous slip that could be intentionally fired to a red or a black color. The color change was the result of not only kiln atmosphere and temperature, but at times also of the degree of vitrification of the slip. Color variations in both the painted decoration and in the clay body of sherds from one archaeological site and time are shown in Figure 6. This series of sherds was excavated at Tell Halaf in northeastern Syria and comes from pottery... 

Finally, the sgrafitto sample could not be assigned to one of the compositional groups. However, it is noted that the Fe content is the highest for this sherd among the studied materials. This feature, together with a relatively medium Ca content, provides a characteristic red color for the clay body. This color, which would be undesirable in majolica, is a desired effect for sgrafitto pottery (22). 

The following section focuses on the variability of the clay bodies or pastes of the glazed ceramics previously characterized by LA-ICP-MS and LA-TOF-ICP-MS. The purpose of this study is to compare the variation in the ceramic pastes with the different glaze decorative technologies through time. The variability in the ceramic pastes will be characterized through instrumental neutron activation analysis (INAA) and petrographic analysis. 

Before elaborating on the different types of clay, it is important to clearly define the terms clay and clay body. A clay is a material with plastic properties, formed by natural forces and found in nature. Some examples are ... 

As the fuel is consumed, one places a metal container over the fire to produce a reduction atmosphere . This is one way to insure that the high black luster will occur on the surface of the pot. While the clay body can contain a high amount of iron oxide, like the clay body used in low-fire earthenware, covering the pots during the firing will cause some coloration irregardless of the amount of iron oxide in the clay body. Potters tend to use whatever metal container is easily available. Salvaged car hoods or metal wash tubs are common. Prior to the introduction of manufactured materials like this, one would cover the fire with a layer of dry dirt or soil. 

While the clay body can contain iron, the reference to cherry red is a reference to temperature. I am giving references that are relevant no matter what the unit of measurement would be otherwise. 1500 °F or Cone 06 would work in the United States, but not everywhere else. I am not sure who your intended readers are, so you... 

In addition to the archaeological material, majolica sherds were obtained from two modern factories in Puebla La Trinidad and Santa Maria. Both of these potteries use a clay body blended from a mixture of equal amounts of a black volcanic clay and a white marl obtained from the immediate area around Puebla (4), Samples from these sherds were analyzed by neutron activation analysis and the data used to represent a Puebla composition. 

The only unique aspect of this type of ceramic work is the addition of chopped strands or small strips of fiberglass cloth to the wet clay body. This can be done with a rolling pin for flat or "slab"... 

Just about any type of low or medium fire clay body can be used. The critical element is maintaining the heat of the firing kiln at or below Cone 6 (about 2174°F). At higher temperatures,the glass strands will melt and flow out of the clay, leaving voids and resulting in a very weak panel. 

From inquiries among Mexican archaeologists and ethnologists it became evident that no majolica is presently produced in the Valley of Mexico, but we found that there is still a small majolica production in Puebla. The majolica manufacturers visited in this city were the La Trinidad factory (Guevara sisters) and the Santa Maria factory (Padierna family). Both manufacturers work in an identical manner and use a clay body blended from a mixture of equal amounts of a black and a white clay. 

The evaporation rate of water in the first stage is always lower than that from a free water surface, e.g. with clay bodies by up to 30%. This fact is explained by a certain depression of water level in the surface pores, in which water vapour pressure is reduced as a result of the negative curvature of the water level. 

FIG. 169. Water distribution during the drying of a clay body (from Norton, 1952). 

Dear [33] described the mechanism of attack as the solution of first the glass, cristobalite, and other forms of silica in brick, followed by the solution of the finely divided mullite and clay body. The presence of well-crystallized mullite needles at the slag-interface indicated that the liquid at the contact surface was enriched with alumina. 

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