Porcelain clay is a mixture of kaolin, quartz and feldspar, in varying proportions. Kaolin, a pure, highly refractive clay, gives porcelain its translucency and whiteness. Feldspar acts as a fluxing agent during the firing process, while quartz provides pieces with their shape.
Porcelain may be produced according to different processes, depending on the type of product and characteristics intended.
Hollow pieces, such as tea and coffee pots, are produced in the pottery area using a technique known as moulding. Moulding involves the pouring of liquid porcelain clay, also known as slip, into a plaster mould. The formation process will depend on the absorption capacity of plaster and the time slip stays inside the mould. The mould is drained as soon as the clay layer reaches the desired thickness, in order to remove excess slip. Once dry, the piece can be finally removed from the mould.
Complex pieces, such as sculptures, often need to be manufactured as separate parts, which are subsequently glued together. This technique requires great experience and skill by the artisans involved, in order to ensure the quality of the final product.
Flat pieces, cups and symmetrical pieces are produced through a special moulding process whereby malleable porcelain clay is placed inside a clay mould and pressed against its surface by a rotating metal head.
Once dry and finished, pieces are fired at a temperature of approximately 980°C.
A transparent vitreous coating is subsequently applied. The objective of this process, known as glazing, is to provide pieces with a glossy surface, pleasant to the touch.
Once glazed, pieces are fired a second time, at a temperature of approximately 1400°C. This stage is essential for pieces to become glossy and translucent.
Pieces undergo stringent selection and quality control procedures throughout the entire production process. All white china is selected manually.
Porcelain decoration techniques include image transfer, application of rims and hand or airbrush painting.
Images are transferred to fired porcelain pieces using transfer paper with a protective film coating (lacquer). The backing comes off when the transfer paper is immersed in water, allowing images to be applied to the piece.
Airbrush painting requires great skill by the painter, who is responsible for preparing the colours and ensuring their even application.
Following the Vista Alegre Painting School tradition of producing pieces of the highest quality, hand painting is reserved to pieces of great artistic and commercial value. Relying on specialised, highly qualified artisans, Vista Alegre is one of the few ceramic factories that boasts a fully operating hand-painting workshop, where pieces are produced according to stringent technical requirements. All painters employed by Vista Alegre have profound knowledge of colour palettes, correct paint application techniques and the behaviour of all materials during the firing stage.
Visitors to the Manufacturing section are given the opportunity to observe the porcelain decoration techniques most widely used at Vista Alegre and to be fascinated by its exquisite pieces, limited editions, personalised orders and pieces decorated with coats of arms.
Decorated pieces are required to undergo a final firing step in a muffle, also known as a decorating kiln, whose temperature does not exceed 860°C.