The fascinating world of porcelain production

Isostatic dust-press moulding of plates is another method. This involves a porcelain paste consisting of minute spray-dried granules. These granules are poured into the press mould and bond under high pressure. The press tool required is divided into two parts, the upper and the lower die. The upper die is used to shape the top of the item and has to be rigid. The lower die shapes the back of the item and is fitted with an elastic membrane to isostatically mould the pieces. When the upper and lower dies are closed, the granules are pumped into the hollow area inside using compressed air. The item is moulded under pressure of approximately 280 bar, thereby ensuring it is evenly bonded. Dust-pressed items have to be smoothed off around the rim only. The normal finishing process follows after that. Press moulding is a high efficient method and among its many advantages is a significant quality improvement in the production of plates and platters.

This method is used in the production of square and oval platters. The porcelain slip is pumped into a two-part, porous plastic mould and then put under pressure. The water escapes through the open pore canals of the plastic mould while the porcelain paste stays within. When finished, the mould opens automatically and a suction pad lifts out the pieces.

Photo: The cast and still very soft body leaves the plaster mould for the first time.

Black porcelain is a special Rosenthal product. As precious a porcelain as “porcelaine noire” should never be put in the dishwasher. It is best to wash it by hand in warm water and to dry it immediately with a soft cloth. Sustained contact of crockery with food containing lemon or acetic acid should be avoided as staining could occur. Black porcelain should also never be used in the microwave oven.

The undecorated porcelain, also called finished white ware, is carefully sorted by highly skilled personnel. The intrinsic characteristics of the materials and the ceramic production process, especially the firing, inevitably cause tolerances and minute deviations between individual pieces. The sorting process accurately separates out the items with such levels of deviation and discards altogether pieces with defects.

Through their colours, decorations on porcelain enliven the white of the material. A vase or a dinner service, 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. Moreover, a variety of decorations appeal to different consumer tastes. Hence the Product Development Division offers a whole host of decorations created by renowned artists, using the strictest criteria in selecting the best designs.

Lustre, gold and platinum bands, handles, spouts and gilded reliefs are all hand painted. after firing, fibreglass brushes are used to burnish the gold layer to a high gloss.

Photo: The iconic head of Medusa adorning the Rosenthal meets Versace collections is gilded by hand and looks brown in its unfired state.

There are several methods to produce the combination matt – glossy.

1. Matt glaze is sprayed onto the porcelain in a similar fashion to a colour base using a spray gun and then fired.
2. Glazed porcelain can be made matt by sandblasting.
3. The areas that are to remain matt and unglazed are covered with wax before being dipped into the glaze. The wax burns off during sharp firing.