Synergistic engobe coating composition and process for manufacture of colored engobe coatings and coated terracotta articles and ceramic tiles

Novel engobe coating composition and a process for the manufacture of colored engobes as coatings and coated terracotta articles and ceramic tiles, are disclosed. The engobes made from platelet shaped transparent substrates like mica, talc or glass coated with metal oxides or metal hydroxides along with/without alkaline earth metal compound and with aluminum oxide for use as pigments in cosmetics for use at ambient temperature or as pigmenting glazes and enamels for very low to medium temperature applications are not suitable for terracotta articles, ceramic tiles and novelty wares for medium and high temperature applications. The composition is also based on some specific raw materials available in a specific region or a country and thus, suffers from limited use. The compositions of engobes possesses yellow and other color decorations and consists of naturally occurring common clays as the major ingredient and talc powder, titanium dioxide and de-flocculants as minor with the optional presence of dolomite and additional transitional metal compounds as colorants for universal applications on terracotta articles and ceramic tiles. The engobes form an impervious vitreous coating on to terracotta wares and ceramic tiles fulfilling the requirements such as surface smoothness, good adherence to the article, good frost resistance, color stability with a matt finish, chemical durability and resistance to weathering, abrasion. The engobes also avoid the use of glaze as second coat over the engobe coat and thus, make the production process more economical