Learn about ceramic glaze
1. What is ceramic glaze
Ceramic glaze is a layer of glass about 0.15-0.4 mm thick covering the ceramic bone surface. This glass layer is formed during the firing process and it has the effect of making the surface of the product more dense, smooth and shiny.
2. Formulations and ingredients
A) Formula
In the glass industry, the percentage of constituents used is comparable, but in the ceramic industry people use the molecular weight and, of course, can switch back and forth between the two. Seger proposed the arrangement of the oxide in the yeast into three main groups: base oxide, acid oxide and amphoteric oxide. These groups are arranged in the following order and this set is called the Seger formula of yeast.
B) Materials
Ceramic glaze is a complex system composed of many oxides such as Li2O, Na2O, K2O, PbO, B2O3, CaO, ZnO, MgO, Al2O3, Fe2O3, SiO2 ... are included in the following forms:
Plastic materials: kaolin, clay, talc (steatite), concrete ...
Nonplastic materials in mineral form: including agar, dolomite, limestone, sand ...
Non-flexible materials in the form of industrial chemicals: BaCO3, Na2CO3, K2CO3, borax (folk called the borax), boric acid, Cr2O3, ZnO ... or frit.
Ceramic glaze, in essence is glass, but the way it is mixed is not exactly the same. Because conventional glass when heated can be in the stirred tank for homogenization and defoaming. The melted ceramic melt must be uniform without any mechanical assistance. Therefore, there should be no material that can not make glass phase.
Therefore, it is essential first to create a uniform liquid flow at the desired temperature. During the melting process and soon thereafter, the oxide in the glaze reacts with the ceramic bone surface to form an intermediate layer. This reaction is very important because it affects the mechanical strength of yeast. It does not just depend on the chemical composition of the yeast but also depends on the oxide itself.
It is necessary secondly that the chemical composition of the yeast should be similar to that of the ceramic bone. Cooling (cooling) occurs in contrast to heating (heating). If the thermal expansion coefficient of yeast and bones do not match, it will cause cracking or cracking. Therefore, the third essential is that the thermal expansion coefficient of yeast and bone must match.
Melted men must be hard, smooth, glossy (except yeast mat). Besides, the transparency, colorless, shiny glaze of yeast is not always as desired. If the ceramic bones are colored, they must use chisel to cover the color of the bones. In addition, it is possible to make enamel (surface like wax), crystalline enamel and countless glaze colors.
It is ultimately necessary that the composition of the yeast be adjusted so that the yeast possesses the desired physicochemical properties Vietnamese pottery.
