Direct enamel frit are used for preparation of glazes on floor and wall tiles and other products of architectural, sanitary, utility and art ceramics. Frits are divided according to their characteristics and use into main groups, secondary groups and subgroups.
In agreement with this classification, the marking of direct enamel frit consists of two letters, a group of 5 digits and a letter at the end of the marking.
Letters specify the classification in the corresponding main group: the first letter indicates the use of the frit (C stands for ceramic), the second letter indicates the characteristics of the fired glaze which was prepared from the indicated frit.
In the following group of five digits, the first digit specifies the colour of the glaze. The next two digits indicate 1/10 of temperature in a hot-stage microscope, at which the pellet prepared from the milled frit has the shape of a hemisphere. The determined temperature is rounded off upwards or downwards within a range 200C (at a temperature over 10000C, the value 10000C is subtracted). Further digits indicates the use of the frit, the last digit indicates the serial number in the corresponding group or subgroup.
The letter at the end of the frit marking indicates the form in which the frit is being supplied.
Direct enamel frit are divided into the following main groups according to their use and visual characteristics:
direct enamel frit for preparation of glossy glazes – marking CL
direct enamel frit for preparation of semi-glossy glazes – markingCS
direct enamel frit for preparation of matte glazes – marking CM
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