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Since ancient times people have enjoyed decorating articles used in their everyday life Through their colours, decorations on porcelain enliven the white of the material, creating a vivid contrast to the plain white shape. A vase or a dinner set, richly decorated in gold, is an elegant and stately embellishment for formal occasions, whereas the same pieces decorated with a colourful floral pattern assume a friendly and cheerful character. A colourful pattern can help to set the mood for certain purposes and occasions. Besides, a variety of decorations appeal to different consumer tastes. Hence the Product Development Department offers a host of designs and patterns created by artists and designers of international fame, using the strictest criteria in selecting the best.
The most frequently used technique for decoration porcelain is the application of a sheer, wet colour film. This process demands extreme precision, patience, a steady hand and a sharp eye. The expressions "sliding print" and "transfer" create a totally wrong impression of what is involved. The transfers are printed by a special flat- or silk- screen process. These days they are no longer used to decorate tableware alone, they are also applied to valuable limited porcelain editions, which cannot be painted by hand without altering the original design of the artist. A porcelain painter cannot simply copy a design by an artist. The reproduction of designs by eminent artists on to porcelain has been made possible by using new, elaborate printing techniques which produce a perfect replica in ceramic colours.
Lustre, gold and platinum bands, gold etchings and gilded reliefs are hand painted. The gold is applied in two layers and fired after each application. Fibreglass brushes are then used to burnish the gold to a high gloss. After the final firing, the hand painted decoration contains as much as 95% pure gold (22 carat). All figurines are also painted by hand. There are two methods: on glaze when the figurine is decorated after the second firing, and under glaze when the biscuit fired figurine is painted before being glazed and fired.
When larger areas of a porcelain piece are to be coloured, the colour foundation is distributed evenly with a spray gun. All areas that are to remain white are varnished beforehand with a lacquer that must be removed after spraying. After removal of the varnish and before firing, the white areas of the porcelain are cleaned carefully. Even the tiniest colour residue turns into visible spots.
Decorative transfer printing
Thanks to new printing techniques it is no longer the case that only hand painted porcelain is of true value. These days the artists design is scanned into a computer and reworked by an elaborate software programme in order to make it fit onto each piece of a dinnerware set, adapted to its three-dimensional shape. The character of the artists "signature" is fully preserved. After this process the design is printed onto specially prepared paper spread with a layer of glue. This makes it easier to lift the colour decorations off the paper and onto the porcelain. The colours are applied on to the paper by using the screen-printing method. Very finely meshed metal screens allow the colour to permeate only in desired areas. Each colour is printed separately, which means that a new screen has to be prepared each time. The different colours are printed one after the other and aligned exactly. Screen-printing allows a strong application of colour which after firing produces a rich glow. After printing the transfer sheet is coated with a layer of lacquer. Before decorating a porcelain piece, the sheet is soaked in water to dissolve the lacquer. The flimsy and wet colour film is then carefully applied to the porcelain.
To produce the very valuable gilt-etched border, parts of the decorations are etched into the glaze using hydrofluoric acid, the only acid that affects porcelain. The parts that are not to be etched are protected with a coat of varnish beforehand. The longer the porcelain is dipped into the acid, the deeper the decoration is etched. Precise timing is essential for consistent quality. Afterwards the decoration is gilded twice by hand. Each coating of gold has to be fired separately. After the second firing, the gold is burnished to a high gloss with glass fibre brushes.
Combination matt - glossy
There are several methods to produce the combination matt - glossy. A matt glaze is sprayed onto the porcelain in a similar fashion to a colour base and then fired. Glazed porcelain can be made matt by lightly etching in hydrofluoric acid. The areas that are to remain matt and unglazed are covered with wax before being dipped into the glaze. The wax, shown here in blue, burns off during firing.
Under glaze decoration
An under glaze decoration is often hand painted onto the porcelain whilst it is still porous after the first firing. The decorated article is then glazed and fired at approximately 1400 degrees C. Even the company logo (backstamp) is applied before glazing. There are only a few colours that can withstand the high firing temperatures: cobalt blue, green, brown, a pale yellow and a mixture of these colours from grey to black. Designers like to combine the under glaze cobalt decoration with gilt-etched decoration.
High temperature decoration firing
High temperature decorations are either transfer-printed, hand painted or sprayed on to the glazed porcelain.
In contrast to under glaze firing, considerably more shades of colour as well as gold and platinum can be melted into the glaze. In only 90 minutes the porcelain is heated to 1250 degrees C so that the decoration sinks into the liquefied glaze which is protecting it at the same time. Inglaze decorations remain unaffected by outside influences and are dishwasher safe.
Similarly, onglaze decorations are applied to the porcelain, using transfers, spraying techniques or hand painting. This procedure permits the use of vivid colours, such as red and orange that cannot withstand high temperatures. Also the rich gold, platinum and lustre decorations are fired onto the glaze at temperatures of between 800 and 900 degrees C. Onglaze patterns are not as smooth as glaze normally is and are detectable to the touch. Elaborately decorated porcelain are fired up to six times:biscuit firing, sharp firing & 4 decoration firing processes. "Aida" (the Rosenthal service), featuring a cobalt blue rim and an acid-etched gold border, is fired just as many times: biscuit firing, sharp firing, cobalt firing (inglaze decoration firing), 1.gold firing process, 2.gold firing process & corrective firing, if necessary.