What is the reason for affecting the whiteness of kaolin?
The two major factors affecting the quality of kaolin are: whiteness and brightness, and whiteness is the reflectance of kaolin to 3800-700 wavelength light.
Definition of whiteness:
The whiteness is 90%, which means that the reflectance is equivalent to 90% of the standard sample. The brightness is equivalent to the whiteness of 4570 wavelength light. The measurement method is the same as the whiteness. This index is an important reference quality index for papermaking, paint and industry. Whiteness requirements are specified for China's kaolin product quality standards, and there is currently no specification for brightness.
Factors affecting kaolin whiteness:
Usually, kaolin has a small content of V, Cr, Cu, Mn, etc., and has little effect on whiteness. The mineral composition and content of iron and titanium are the main factors affecting the whiteness of kaolin. The forms of iron ore include pyrite, limonite, hematite, rutile, chlorite and so on. Their existence not only affects the natural whiteness of kaolin, but also affects the whiteness of calcination, which makes the pigmentation and melting of porcelain different. The iron impurities in kaolin not only affect the color of ceramic products after calcination, but also seriously affect the dielectric properties and chemical stability of ceramics. Therefore, the removal of iron impurities in kaolin plays an extremely important role in the better use of kaolin.
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