Ceramic Techniques

The manner in which colours have been applied to a ceramic surface offers reliable clues to dating an item. Clues which can be seen by the naked eye or better still under a normal lens with a magnifying power of three to ten magnitudes.

In the past the paintbrush was the only means for painting pottery. The loaded paintbrush empties the paint continuosly and the layer of paint becomes thinner as it moves across the surface. This gradual reduction in the quantity of paint on the brush creates subtle differences in the shade of colour lending greater liveliness to the images.

The rising labour cost faced by factories in the eighteenth and nineteenth centuries led to a widespread search for new mechanized means of decorating pottery. The first to introduce transfer printing was the English ceramics industry. The first transfer prints were black and wear applied over or also under the glaze. After 1750 cobalt blue was preferred and used under the glaze. Pieces using this technique cannot therefore have been manufactured before 1750. This technique consists of coating a copperplate with a thin layer of acid-resisting was onto which the etcher draws his design, exposing the bright metal underneath. The plate is then immersed in a bath of diluited acid. The Etched plate is inked and the surface wiped, leaving the ink only in the design. Finally the plate is passed through two rollers and pressed against absorbent paper which, while still wet, is pressed against the surface to be decorated, transferring the engraving to the pottery, which is then put in the oven.

The deeper the incision on the copperplate, the greater the amount of colour transferred.

Modern printing techniques, like those using photo mechanical processes,were applied almost contemporaneously also for the decoration of pottery. The application of colour is uniform.

The variation in thickness of the layer of paint and the consequent range of shades created permits a handmade brush stroke to be clearly distinguished from a printed pattern.

Towards the end of the 19 th century the four-colour lithographic process was introduced for transfer painting on porcelain. A piece decorated by this method can therefore not dated to before 1880. In modern reproduction we can see the tiny coloured dots typical of the printing process instead of the touches of colour left by a brush.

The quality of the painting is of prime importance in determining the commercial and artistic value of a ceramic item. It would be advisable however to adopt different criteria for assessing Asian and western production. Brush strokes of the fineness we can admire for instance on Chinese and Japanese pieces can be executed more easily by the skilled hands of Asian painters than by European artists as the art of using the paintbrush for writing is taught to the Chinese and Japanese from childhood.