Porcelain manufacture
Though the porcelain production process becomes more and more mechanized, it nevertheless remains a long and still complex process.
1. Creation
The various items are designed in plaster or by computer. The article is designed larger than required from 14% to 16%, to allow the shrinkage of the body during the manufacturing process (drying and firing stages). The new article or the prototype is then handed over to the modeller.
2. Modelling
The modeller creates the first mould and the core or matrix, which will accurately, reproduce each part of the first mould.
The traditional moulds are made in plaster for the sake of their qualities of porosity and drying which allow the plaster to absorb water.
The new manufacturing techniques have made it possible to use:
- Mould in porous resin (pressure casting),
- Flexible membrane on steel support (isostatic pressing).
3. Preparing the body
Pillivuyt focuses on maintaining the know-how born of its tradition and remains one of the few porcelain producers which elaborates its paste according to its own formula from selected and systematically controlled raw materials.
The use of distinct production process (casting, jiggering, pressing) request clays of different formulations.
- For casting, a liquid mix is poured or injected into plaster or resin moulds.
- For pressing, a solid elastic body is pressed on jiggering machine fit with plaster moulds or a special clay granules are injected into an isostatic press.
Clay granules are bought from specialised providers. The body is in the form of granules (2,5% moisture content). It is used for manufacture in isostatic press (300 bars pressure) plates, saucer, some of our main dish. The other forms of body are elaborated internally.
4. Manufacturing process 
Casting
This is the process by which complex pieces such as teapots, jugs, and casseroles are manufactured. The slip used for casting is distributed under pressure to each workstation.
There are 3 processes
- Open top casting in drain mould. The slip is directly poured in the mould. The plaster gradually absorbs the water in the slip. A crust of clay is deposited on the inner wall of the mould. The piece is removed from the mould 30 to 45 minutes later, depending on the type of piece. Fittings such as spouts, handles, decorative ears, and knobs for covers must be added at this stage of manufacture. They are affixed or "luted" to the pieces with slip.
- Solid casting in a closed mould. The slip is poured in through a funnel-shaped vent. The empty space within the mould and the filling holes are filled with slip. This technique is used for ashtrays, ramekins and some dishes. Since the various moulds have to dry, only 3 to 4 cast are possible per day.
- Pressure casting. The casting is carried out under pressure (about 25 bars) in moulds made of porous resin. The press can make four pieces simultaneously at a rate of 100 cast per shifts of 7:30 hours.
The main advantage of this technique is that the resin moulds make possible the manufacture of thousands pieces (30.000 in average) whereas plaster moulds produce only about 60 to 100 pieces. Moreover, this type of mould turns in 24/24H whereas a mould plasters produces only 2 pieces/day taking into account the time of drying. Thanks to this technology, the manufacturing cycle has been reduced by half.
Forming
This is the process by which thrown ware is manufactured, for example saucers, plates, cups, and salad bowls…
A steel head squeezes the body onto the plaster mould and imparts the desired profile. Drying and finishing complete the operation.
Isostatic pressing
The granular body is injected under pressure (300 bars) in the mould of the press.
5. The biscuit firing
This is the term used to designate the first firing, which take place in an oxidant atmosphere at 980°C / 1 000°C (1 795°F to 1 830°F) It causes organic matter contained in the body to be burned up and removes the water in the clays and kaolins. The duration of firing is about 16 to 18 hours. This firing makes the pieces rigid and porous (20% porosity) for the next operation: glazing.
After this firing the pieces are sorted, dusted, and marked with a stamp.
6. Glazing 
The glaze is made of water, silica, pegmatite, kaolin and lime, which imbue the porcelain with its smoothness and brilliance after firing.
Two processes are used :
- Dipping in a bath of glaze :
• By hand (all type of pieces)
• By machine (plates)
- Spraying :
• By hand
• By glazing robot
After glazing, the pieces are fired a second time at 1 400C° (2550°F).
7. Second firing : the glost firing
The pieces are fired either in a tunnel kiln or an intermittent kiln. The firing cycle of the tunnel kilns last 27h30 while that of the intermittent kiln last 19 hours. The temperature of the glost firing is as high as 1.400C° (2.550°F), to produce pieces that are white, non-porous and perfect cleanliness.
8. Sorting
On coming out of the kiln, the pieces are sorted and classified according to well-defined quality standards. It's also at this stage that the unglazed parts of the ware are polished.
9. Decorating
Lining done by hand
This is done manually with a paintbrush, using a turntable rotated by the operator. This technique is mainly used for short runs and difficult items.
The specialist distinguishes between :
- A hairline (0.5 mm wide)
- A filet (2 mm wide)
- A band (3 to 5 mm wide)
- A covered-rim filet
- A counter-hairline
Lining done by the machine
The process is used particularly for long runs, plates, saucers and oval dishes.
Spraying
The colour is applied with a spray gun. This type of decoration is particularly interesting on pieces with relief, because it's possible to create more or less coloured zones.
Decalcomania
It is the process most commonly used. Each decoration is a type of transfer (chromo) applied by hand on each piece.
It takes the form of a fine transparent film known as a slide -off on which the design is printed.
The decal operator removes the slide-off from the paper backing by moistening it and then places it very carefully on the items to be decorated. Using a piece of cloth, the operator presses out all the water and air trapped between the film and the items. The smallest air bubble would explode during the firing and cause a fault in the decoration.
10. Third firing : the decoration firing
The decorated porcelain then undergoes a third firing of about 2 hours. The slide off disappears during the firing, leaving the printed decoration.
Two sorts of decal are distinguished :
- "Low temperature", fired at a temperature of 900°C (1 650°F), the decoration remains on the surface of the glaze.
- "High temperature", fired at a temperature of 1.200°C (2 190°F), the decoration penetrates the glaze and remains indelible. This patterns are dishwasher safe.
