The summary is as follows.
1. Lead glaze and lead-free glaze
In the lead glaze formula used in architectural ceramics and sanitary ceramic products, the source of lead comes from lead metasilicate or lead borosilicate fusion. piece. In actual production, the typical lead metasilicate formula composition is: Segel formula 1.00 lead oxide, 0.10 aluminum oxide, 1.89 silica, weight ratio: lead oxide 64, alumina 3, silica 33). Provides minimal solubility of glaze. Increasing the content of alkaline oxides and boron oxide can lead to an increase in lead solubility in the frit. In countries such as the Netherlands, there are no restrictions on lead solubility. They use low-melting or high-soluble lead silicate and lead borate frit glazes. The difference between lead glaze and lead-free glaze involves product quality issues. However, above 1150℃, lead is obviously volatilized, and above this temperature limit, lead glaze is usually no longer used. Lead-free glaze refers to the type that contains less than 1% lead oxide by weight. As environmental protection requirements become more and more stringent, the ceramics industry in various countries has gradually shifted to the use of lead-free glazes, lead-free fluxes and lead-free pigments.
Strontium glaze has shown good results in replacing lead glaze. In addition to a wide firing range, low firing temperature and the ability to form a glossy glaze surface, it also has good wear resistance. Therefore, strontium glaze becomes a good lead-free glaze. When it is used with underglaze colorants, there is almost no adverse effect on the colorants. However, when used with chrome tin red, it must be added to the glaze. A certain amount of calcium oxide to stabilize the tone quality.
2. Raw glaze and frit glaze
Since frit is not used in the composition of ceramic raw glazes, they are limited to use when the maximum firing temperature is greater than 1150°C. It can usually be used for glazing in the production of hard porcelain, vitrified sanitary porcelain, stoneware, electric porcelain and various low expansion bodies. Raw glazes contain mineral solvents such as feldspar or nepheline syenite, plus clay, quartz, calcium carbonate, dolomite, zinc oxide and zirconium silicate as common raw materials. Low-expansion raw glazes also use hectorite as a flux. Raw glaze will not have any form of glass phase. Sufficient time must pass to exhaust the gas from the raw material components during firing. After the glaze is melted, a smooth glaze without bubbles can be obtained. Therefore, the firing time of raw glaze Longer than frit glaze. When the firing temperature is lower than 1150°C, frit glaze should be used. In addition, when using the low-temperature fast firing process, the frit content in the glaze needs to be increased accordingly.
3. One-time firing glaze and two-time firing glaze
For ceramic enterprises, one-time firing of glazed products is more energy-saving and more economical than two-time firing. Reduces product costs and benefits environmental protection. One-time firing is very beneficial for high value-added products, such as large sanitary ware, or large insulators. But the main advantage of secondary firing is that it can select and eliminate certain defective semi-finished products, and it can also produce high-quality and low-cost products. In the one-time firing process, the glaze and the green body mature at the same time. The formation of the intermediate layer between the green body and the glaze can often increase the strength of the product, and the complete vitrification of the green body is also obvious. During the primary firing process, the glaze often contains a binder, which can not only control the evaporation rate of water from the glaze slurry, but also control the movement of water into the porous blank. Glaze binders increase the hardness of the dry glaze.
4. Colored glaze and colorless glaze
Building sanitary ceramic products are generally decorated with colored glazes, so that they can also have an appreciable aesthetic feeling when used, which improves the The added value of the product. The application of colorless glaze is limited to a small range of products (such as special-purpose ceramic tile products). The color glazes of European architectural and sanitary ceramic products are all prepared with metal oxide pigments. Inorganic compounds of transition metals such as vanadium, chromium, manganese, iron, cobalt, nickel, and copper are commonly used pigments. The effect of color glaze depends on the chemical composition of the base glaze, the amount of color added, the thickness and uniformity of the glaze, and the kiln atmosphere during firing. For example, the form of iron oxide introduced is usually red trivalent iron oxide, which can be blended into the glaze to produce a subtle decorative effect. When iron is in an oxidizing flame atmosphere, it can produce light yellow, honey color and brown color in the ceramic glaze. Light bluish gray, green, blue or black can be formed in the reducing flame atmosphere; black cobalt oxide is the strongest colorant in the glaze, and when the content is less than 1, it can form a bright blue.
As a high-grade ceramic art glaze, the crystalline glaze's beautiful and novel natural crystal flowers, as well as its diverse appearance and colorful colors, give people a strong artistic effect and are very popular among users at home and abroad.
In addition, the building and sanitary ceramics industry has accelerated the use of high and new technologies to promote the development of new glaze technologies, developed new varieties of glazes and glaze colors, and has made a lot of progress. For example, the application of nanomaterial technology in glaze technology, etc., a large number of new products are launched every year. In general, focusing on glaze technology innovation and new product development can improve product quality and added value. With the continuous increase and enrichment of the varieties of building sanitary ceramic products, many new requirements have been put forward for the improvement of glazes. Therefore, the research and development tasks of ceramic glazes will become increasingly larger in the future, and they will occupy an increasingly important position in the competition in the international ceramic industry. my country's ceramic industry should speed up the absorption of advanced technology, continue to improve the grade and technological content of its products, and gradually form its own glaze product system and decorative features.
Low temperature: around 800 degrees, medium temperature around 1100 degrees, high temperature: 1280--1400 degrees, crack glaze is fired at high temperature {1280--1340 degrees}. Shadow celadon glaze is fired at high temperature {1280--1280-- 1320 degrees} can be fired side by side on the same body. Crack glaze and shadow celadon glaze cannot be mixed together. Pay attention to the operation. Mixing crack glaze may prevent cracks.