Coatings, blanc fixe

Chemical composition is another factor which determines quality, particularly in chemical and medical applications but also in paints and coatings where it affects brightness. Barium is highly toxic but only in the form of water soluble salt therefore in every application the water soluble barium must be controlled. Other usual admixtures contain iron, copper, manganese, and lead, and depending on application, their concentration is also restricted. Natural products contain 94-99% BaSO4, whereas blanc fixe contains horn 97.5 to over 99%. 

Classification. Extenders are mainly natural minerals that are converted into a usable form by working natural deposits, separating secondary constituents, and comminution (micronization). Synthetic products such as precipitated carbonates [e.g., calcium carbonicum praecipitatum (ccp), precipitated sulfates (e.g., blanc fixe), precipitated and pyrogenic silica, and silicates are used for optical brightening. Synthetic fibers (generally organic) are used for reinforcement. The classification of extenders used in surface coatings is summarized in Table 4.1. 

Paper Coating kaolins, titanium dioxide, talc, calcium carbonate, plastic pigment, blanc fixe, satin white, zinc oxide, structured kaolin pigments. 

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