THE MAKING AND DECORATING OF OUR POTS
Different types of clay are selected according to their plasticity and colour.
Our clay comes from a quarry in Germany where silica compounds are added to the natural clay to improve it’s plasticity and the subsequent mixture is then washed.
After decantation, the clay has it’s excess water removed in a filter press, and then it is mixed and deaired in a pugmill.
The clay obtained is ready for use. We often mix this clay with our reclaimed clay (this is waste clay, not yet fired, and mixed by hand).
THE MAKING PROCESS IN BOURZOLLES
All our work is made with one or more of the following thechniques:
Throwing: 90% of our production is thrown by hand on an electric wheel. These pieces are the turned when partly dry, to improve and finish their contours and make their feet.
Jigger and jolly: This is a machine on which a rotating mould has clay spread into it to create different forms. It is particularly useful for making flat pieces and plates.
Press moulding: This is a manual method for spreading clay into moulds and is used to make pots which are oval or square
The additions, (handles, knobs, spouts e.t.c.) as well as any relief decorations, are added when the pots are half dry or " leather hard ". Finally Enleve tiret en bas de para the first firing para 1 being fired for the first time in the biscuit firing.
THE FIRST FIRING
When the pots are finished, they are left to dry for a few days before being fired, for the first time, in the biscuit firing.
The aim of this process is to permanantly change the raw clay into pottery and make subsequent glazing on the solid pot much easier. The firing reaches approximately 1000° in our gas kiln, and takes about 8 hours.
HIGH FIRED DECORATION AND THE SECOND FIRING
During this firing the clay undergoes no further permanent:
From 0° to 120°: The remainder of the pore water in the clay is driven off, by the heat, in the form of steam.
This stage is extremely delicate and takes around 12 hour cooling period to allow change
From 120° to 350°: The organic matter in the clay decomposes.
From 350° to 700°: The ceramic change takes place. The water, which is chemically bound in the crystal structure of the clay, is driven off. This enables the particles to come into contact with one another and to weld at these points. This process begins gently between 350° and 450°, and reaches it’s peak at around 600°.
From 700° to 900°: The carbon and sulphur compounds are burnt out of the clay body.
From 800° to 1000°: Vitrification process. The soda and potash compounds in the clay start to flux the silica (which is the major ingredient of clay) causing these particles to melt with one another. This fusion process makes a harder and less porous material.
When the kiln has cooled for about 12 hours the pots are unpacked. These fired pieces are then glazed, by immersion, in a mixture of borax, tin oxide, silica and clay compounds, all suspended in water. This glaze is called " stanniferous " because of it’s tin content.
The glazed object is left to dry. After a few minutes the bottoms of the pots are sponged to remove the glaze. This stops the pots sticking to the shelves in the kiln when the glaze melts.
HIGH-FIRED DECORATION AND THE SECOND FIRING
The glazed pots have a powdery surface when dry.
The decorator paints free-hand directly onto the glaze with metal oxides: cobalt, iron, manganese, copper, antimony and varios mixtures of oxides. This process demands great dexterity and much practice, and once the designs are drawn it is practically impossible to rectify, erase or change them because of the porous nature of the glaze in it’s powder form.
The decorated pots are packed into the electric kiln without touching each other. They are then fired to between 960° and 980°.
During this second firing, the clay unedergoes no permanent change as the temperature does not exceed that of the first.
The glaze, however, begins to melt at around 600°, and reaches maturity between 960° and 980°.
This firing lasts about 8 hours and is followed by a 24 hour cooling period to &allow the glaze and the clay to cool at the same rate.
We then check the pots for faults and blemishes, and finally they are put on sale in our shops.
Route de Salignac
Bourzolles - 46200 Souillac
8 Place Doussot - 46200 Souillac