Feldspar

Feldspar is the name given to a group of minerals distinguished by the presence of Alumina and silica (SiO2) in their chemistry. This group includes aluminum silicates of soda, potassium, or lime. It is the single most abundant mineral group on Earth. They account for an estimated 60% of exposed rocks, as well as soils, clays, and other unconsolidated sediments, and are principal components in rock classification schemes. The minerals included in this group are the Albite, Anorthite, Orthoclase, Microcline and Plagioclase Feldspars.

Iran has many active mines of Feldspar and has a great potentiality for exporting. Marjan Mineral Company will be pleased to provide necessary condition for exporting Feldspar. Marjan Mineral Company can make any trading communication with Feldspar Suppliers in Iran. Read more . . .

Feldspar Usages:

Engobe & Glaze: Engobe is a layer for covering the surface of the clay bodies with a different color. It gives a smooth surface to the Tile after application. The color is provided to the Engobe composition by addition of small amounts of metal oxides. Therefore the Tile can have an aesthetic appearance with different colors. Engobes are sometimes also called as slip or as an intermediate layer between clay body and Glaze. Glaze layer is applied on the Engobe layer as a final coating layer to impart a shiny appearance to the clay body. A low-melting additive of frit is often incorporated into the Engobe mixture to assist earlier vitrification upon firing. There is often less proportion of frit in Engobe than in Glaze. The latter is more glassy than the former. The amount of frit adjusts the hue of the Engobe color and the surface brightness. This is the reason why the Engobes are less shiny than Glazes. This property of the Engobes also provides the diffusion of the gas. In other words Engobes have a porous structure. Since the melting of the Engobe eventuates locally during the firing process. Porous structure of the Engobe allows passage of gases that may form during firing of the ware. If the Engobe layer is completely vitreous then gases cannot escape and blowholes can from, marring the surface of the ceramic. Read more . . .

For a good covering of the substrate, Engobe composition should be carefully designed. First the body and the Engobe should be compatible together during both drying and firing. This shows the quality of the Engobe. In addition, the firing temperature of Engobe should be near the firing temperature of the substrate. The roof Tiles have a low firing temperature. Therefore this condition is very important for making an Engobe for roof Tile. Secondly, the color of the substrate should be covered completely. The color of the Engobe is affected mainly by the amount of the iron in the Engobe. So, the raw material for making an Engobe should be chosen according to their purities. Finally, Engobe should cover the substrate well without peeling. Defects on the surface are not desired for Engobes. Read more . . .