Under Glazed Lithographs can be applied to biscuitware just as to glazed ware. In lithos, the pattern is printed on a wax film or a simplex paper. The biscuitware is heated to a temperature sufficient to melt the wax and then the litho is pressed on to it. The backing paper is blown off by air jets.
Printing is the traditional method developed many years ago and is invaluable for reproducing fine detail in decoration. The cost of engraving and the shortage of skilled engravers encouraged the use of other methods except on traditional lines.
Silk screen printing has recently made very big advances for the production of lithographs. In some factories, silk screens are now used for printing either direct onto the ware or for transferring the pattern onto paper which is then rubbed down onto the ware or applied by machines using vacuum and air pressure.
If oil containing media are used for printing, it is very much necessary to remove this oil before applying the glaze. This is done at a temperature of around 500oC and in this temperature, the organic liquids vapourise and go out. If enough care is not taken there is danger of pinholes in the glaze or patches where the glaze has refused to take in the dipping. Since it consumes lot of energy, in most of the companies this process is dispensed away and most modern liquids which vapourise at room temperature are used as printing media.
