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Some kinds of decorations

The decorations were always an expression of the time taste. Colors and forms are depending upon the time taste. Beside handpainted decorations it gave printed decorations, sliding picture decorations or decorations with gold or silver. But first around 1930 they find ways to protect some of this decorations against abrasion. I would like to describe here different possibilities of the decoration of porcelain, which are authoritative for the durability of the decoration.

The decoration over glaze:
This kind of decoration can be printed, painted or lay on by sliding picture (for example on a sheet preprinted decoration which will be slided from the sheet onto the porcelain) on the finished glazed piece. So that the over glaze painted colors became a fixed connection with the glaze the melting-point of the colors must be under the melting-point from the the glaze (glaze : ~750°C-900°C). The over glaze decoration was a usual kind of the decoration in 20. century. A protection for the decoration against chemical and mechanical effects does not exist.

The decoration in glaze:
By this kind of the decoration metal oxides are used as colors, which are by a rapid burning procedure with 1200°C - 1300°C into the glaze sink and will be closed from her. This kind of decoration you can make with sliding pictute or painted by hand before the porcelain will be burned. This Dekore is thus protected in the glaze.

The decoration under glaze:
Here the color is painted on the not glazed ceramic. The glaze is laid on and burned on the painted piece. Also this decoration is protected.

The corroding gold decoration:
With this kind of a time-consuming decoration the design with hydrofluoric acid is corroded into the finished glazed porcelain. This is the only acid which porcelain attacks. The surfaces which should be elevated in the decoration are provided before this procedure with a protection. Subsequently the gold in several work procedures is laid on. By this way this decoration get her characteristic expression.

The fond decoration:
By this kind of decoration a color will be sprayed on the burned glaze. Similarly as by the corroding gold decoration the surfaces which are white after completion with the color must be provide with a protection.

It can thus quite be that also an older piece of porcelain has a good protection of the decoration. But caution!! Older pieces have usually also decorations with gold or silver. The melting-points of the precious metals (platinum 1773°C, gold 1064°C, silver 981°C) is most lower than the melting-point from the glaze. Therefor these metals are always over glaze and not protected from abrasion.