Delft Blue - Delftware

History

At the end of the 16th century tradesmen of the Dutch East India Company imported large quantities of Chinese porcelain. This typical white porcelain with blue decorations became very popular among the rich in Europe and in the beginning of the 17th century some potters started to imitate this technique. Soon a large number of factories were founded mainly in Delft and Rotterdam producing large quantities of vases, plates and of course tiles. Initially they copied the oriental decorations but later designed their own scenes with flowers and Dutch landscapes. The tiles were used to decorate the walls and served as isolation to keep moisture outside.

Challenges

During the centuries the Delft earthenware industry had to face many challenges. A new type of clay was discovered in Europe which was far superior to the clay that the Delft pottery makers were using. The English potteries became their worst competitors (Wedgewood) and the quality of the Dutch potteries stayed behind due to lack of innovation. At the end of the 19th century there was only a small part of the once so prosperous industry left. They realised that they had to change their technique completely. Finally the Delft potteries found a mixture of clay that could compete with the former stronger, white English earthenware. From then on, they produced a product that would become world famous: Delft Blue Delftware.

Production process

Clay

The process starts with determining the right composition of the clay. Nowadays this is a mixture of over 10 raw materials like chalk, kaolin, feldspar and quartz imported from various European countries. These are all carefully mixed with water until the liquid substance is nice and smooth.

Casting

Most of the substance will be stored in containers to be used for casting later, a smaller part however is put in a so-called filter press where much of the water is extracted. It comes out as a flexible mass and is then used to make products which are completely round like plates and platters.

All other products are produced by casting the liquid clay into hollow plaster moulds. After the mould has been filled up, the liquid substance stays in for about 25 minutes. During this time the porous plaster extracts the water from the liquid substance leaving a layer of clay on its interior. When the clay has reached the right thickness, the excess liquid is poured off.

Kiln

After some time, the clay is hard enough to be taken out of the mould, seams and irregularities are carefully removed. Then the object is put into the kiln to be fired for the first time, at a temperature of 1160° Celsius (2120° F). After 1 day the object is taken out of the kiln.

Painting

Painters can now paint the traditional decorations on the objects. This is done with a sable's hair pencil, and black paint containing cobalt oxide. The cobalt oxide will set off a chemical reaction during the second firing process, changing the colour from black to blue. Because the paint is water based, the painters are able to create various shades of blue by adding more or less water.

To simplify painting multiple complex decorations, a drawing is made on a sheet of paper first and perforated along the main lines. The drawing is then placed onto the object and with the help of some charcoal powder all perforation are visible on the object itself. The painters can easily follow these charcoal dots and use the same design over and over again.

Glazing

When the painters are finished decorating, the articles still need to be glazed. This is done either by dipping them into the glaze or by spraying. The glaze covers the decoration with a white non-transparent layer. During the second firing process, at a temperature of 1200° C (2192° F), the glaze melts into a translucent layer of glass and the black paint turns blue. After careful quality control the object is now ready for use.

Pictures at Delft Blue Delftware pottery Montagne Aardewerkfabriek