Glue bat printing
Stage 1: engraving or etching the copper plate
| The first stage was to engrave the design into the surface of a copper plate. Engraving means cutting into the metal with a sharp steel tool called a burin, or indenting dots with a punch. Sometimes the plate was oated with a wax which protects it from the acid and is known as a ‘resist.’ The design is then lightly etched as well as engraved. Etching uses acid to bite into the surface of the copper. The plate is first cscratched through the wax. The plate is then exposed to the acid. The acid bites into the copper wherever the design has been scratched through the wax. The result of both engraving and etching is a plate with the design cut into its surface. |
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Stage 2: transferring the design from the copper plate to the glue bat
| In the glue bat method, the printer did not heat the copper plate. Boiled linseed oil was rubbed into the lines of the plate. The surface of the plate was carefully wiped clean, so that oil remained only in the lines. A sheet of gelatine, known as a bat, was then pressed on to the copper plate. This transferred the oil from the plate to the bat. The flexible bat was then peeled off from the copper plate. |
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engraved copper plate and the surface cleaned |
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Stage 3: transferring the design from the glue bat to the pot
| The next step was to support the flexible bat, oily side up, on a cushion. Then the pot was carefully pressed down on to the bat. If the pot had a curved surface like a mug or a jug, it was rolled on to the bat, which then curved around the pot and stuck to it. This transferred the oil from the bat to the pot. Then the bat was peeled off the pot. The pot now had the design printed almost invisibly on it in oil. Powdered colour was then lightly dusted over the pot. The colour stuck only to the parts that were oiled. The design could then be seen on the pot. Usually a single colour was dusted on to the pot. At the Vauxhall porcelain factory between 1753 and 1764, however, different colours were carefully dusted on to different oiled parts of the pot, resulting in the earliest known multicolour prints on ceramics. |
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Stage 4: fixing the print on the pot
The pot had already been dipped in glaze and then fired before the print was applied, so this was an overglaze print. It was fixed by firing at about 750 degrees Celsius, a lower temperature than that of the glaze firing, which was at least 1000 degrees Celsius. The print was therefore less firmly fixed than the glaze below it and might be damaged by wear over time.
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