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The Opacity of Enamel White Cover Coat

The Opacity of Enamel White Cover Coat

  • Categories:Company news
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  • Time of issue:2021-10-20
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(Summary description)The opacity of the white cover coat is formed by the difference in refractive index between the precipitated crystal and the glass.

The Opacity of Enamel White Cover Coat

(Summary description)The opacity of the white cover coat is formed by the difference in refractive index between the precipitated crystal and the glass.

  • Categories:Company news
  • Author:
  • Origin:
  • Time of issue:2021-10-20
  • Views:0
Information

The opacity of the white cover coat is formed by the difference in refractive index between the precipitated crystal and the glass. The cover coat with good opacity has small crystals, the crystal grains are fully dispersed, and the refractive index difference between the crystal and the glass is large. But if the crystal is too small, the coverage rate will decrease instead. (The so-called whiteness is compared with the relative 100% of the white sample of magnesium oxide).

There are three types of white cover coat: antimony white cover coat, zirconium white cover coat, and titanium white cover coat.

 

Enamel antimony white fri: Enamel frit using fluoride and antimony as opacifying agent has been used for a long time. In the antimony white cover coat, if the content of antimony is increased or when cerium oxide or zirconium oxide is added during grinding, the coverage rate will increase significantly. However, although it has a strong opacity, its color is difficult to control. It is often bluish or creamy, and it is not acid resistant. It is not suitable for kitchenware and tableware. Now it has been replaced by titanium dioxide cover coat.

 

Zirconium white cover coat for porcelain enamel: Zirconium white cover coat and titanium white cover coat are both recrystallized cover coat, which have devitrification only when they are fired. Because it has a high degree of milky whiteness, there is no need to add other auxiliary devitrification agents. In order to promote the precipitation of zirconia crystals during firing, the ingredients must contain aluminum oxide and zinc oxide. Due to the presence of oxides such as aluminum and zinc, the acid resistance is poor, and most of them are replaced by titanium white cover coat.

 

Titanium white cover coat for porcelain enamel: Titanium white cover coat is currently the best white cover coat, with good opacity, whiteness, stability and acid resistance, and at the same time easy to manufacture.

 

After the titanium white cover coat is fired, titanium dioxide crystals, anatase and rutile are precipitated from the glass. The crystals precipitated at low temperatures are dominated by anatase, and rutile at high temperatures. The hue of the two crystals is different. Anatase crystals grow slowly, have strong refractive power, and have a slight blue tint in the white. The rutile crystals grow rapidly and are slightly yellow in color. Adding P2O5 to the titanium white cover coat can widen the temperature range of anatase precipitation, and it is not easy to transform into rutile, and a white enamel cover coat with stable color tone can be obtained.

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