The Whiteness And Brightness Of Kaolin

Whiteness is one of the main parameters for the technological performance of kaolin, and high-purity kaolin is white. The whiteness of kaolin is divided into natural whiteness and calcined whiteness. For ceramic raw materials, the whiteness after calcination is more important, and the higher the calcined whiteness, the better the quality. The ceramic process stipulates that drying at 105 ℃ is the grading standard for natural whiteness, and calcining at 1300 ℃ is the grading standard for calcined whiteness. The whiteness can be measured using a whiteness meter. A whiteness meter is a device that measures the reflectivity of light at a wavelength of 3800-7000 Å (i.e. 1 angstrom=0.1 nanometer). In a whiteness meter, the reflectance of the test sample is compared with that of the standard sample (such as BaSO4, MgO, etc.), resulting in a whiteness value (such as a whiteness of 90, which is equivalent to 90% of the reflectance of the standard sample).

Brightness is a process property similar to whiteness, equivalent to 4570 Å; The whiteness under (angstrom) wavelength light irradiation.

The color of kaolin is mainly related to the metal oxides or organic matter it contains. Generally containing Fe2O3, it appears rose red and brown yellow; Containing Fe2+, it appears light blue and light green; Containing MnO2, it appears light brown in color; If it contains organic matter, it appears in light yellow, gray, blue, black and other colors. These impurities exist, reducing the natural whiteness of kaolin. Among them, iron and titanium minerals can also affect the calcined whiteness, causing color spots or melt scars on porcelain.