Engobing is used to expand the color range for the facial surface of brick. A light-colored engobe composition has been developed, using red-fire clays followed by the addition of various pigments, to regulate color. The rheological properties of the engobe slips are studied and the quantity of electrolytes is optimized.Additional methods of finishing a brick surface are needed in order to expand the color range of the facial surface of bricks. One such method is engobing. Together with increasing the architectural -artistic advantages, engobing makes it possible to eliminate surface defects of brick, such as "salting out" and color nonuniformity.On account of the capability of engobes to form a fired surface film that is sufficiently dense so that water from air and dissolved salts cannot pass through the film, such brick does not show seasonal discoloration, and the ability of coloring engobe materials with stable inorganic natural or synthesized pigments makes it possible to expand the color range of articles.The color of a composition can be regulated in a desired manner only if the matrix has a light color. Consequently, the first problem of the present investigation was to develop an engobe composition with a light color based on the red-firing low-melting clay from the Novokubanskoe deposit "Khutorok," the same clay that was used to make the brick itself. Similar materials must be used so that the CLTE of the ceramic base matches that of the coating.It is well known that the decrease of the intensity of the red color of red-firing clays can be regulated by introducing carbonate materials, such as chalk, into the mixes [1]. But, in addition to bleaching, at brick firing temperatures near 1000°C carbonates decrease substantially the capability of the mixes to sinter, since at these temperatures only intense decarbonization of chalk occurs and the alkali-earth components do not act as fluxes. Consequently, cullet was added to the engobe mixes in order to intensify sintering.Mathematical methods of planning, specifically, accumulation analysis, were used to work out the optimal composition of a light-colored engobe and subsequent experiments [2]. The contents of clay, chalk, and cullet (X1, X2, X3) were chosen as the factors controlling the compositions of the engobes.Three-dimensional plots with the ability to project a two-dimensional triangle onto a plane were used as the coordinate system. Scheffe's simplex-centroid plan was chosen to analyze the results.Since the engobe must form on the brick surface a dense, fired, 0.1 -0.3 mm thick layer with low porosity and minimal water absorption, the water absorption, the Mohs hardness of the engobe, and the intensity of red color were chosen as the response functions. The sum of the components for each mixture was equal to 1, so that their values were interpreted as proportions, since the coordinate of any vertex of a component equals 1 (100%) and 0 for all other components. On this basis it is possible to calculate the position of each point inside the triangle a...

The phase state of iron oxides in ceramic brick, obtained with reductive calcination, has been determined by Mössbauer spectroscopy.

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The ceramic materials structure formation with the given esthetics-consumer properties is the most important mission of the modern production and should be based on the knowledge of physical and chemical processes, which are flowing past in masses based on the systems differing in the content of alkaline, alkaline-earth oxides and oxides of iron in clay raw materials.

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