Biscuit: A piece having been subjected to a first firing operation at 1,000°C.

Ready for decoration and glazing, the faience biscuit is porous, whereas the

porcelain biscuit, once fired at 1,400°C, is impermeable.

 

Biscuiting: The first bake of porcelain articles after shaping. This process

confers solidity to the piece that remains porous. It will become porcelain

after being plunged in a glaze and fired.

 

Camaieu: Monochrome decoration using the different shades and lights of

a color.

 

Ceramic colors: These substances generally include a colorless and vitrifiable

flux to which one or more coloring oxides have been added. In their unfired state, these colors are finely ground powders, generally presenting almost the same

color shade they will look after firing, except that they will look much paler be-

cause of the fineness of their grains. These powders are thinned with more or                    

less viscous liquids, such as water enriched with gum or oil of turpentine – accord-ing to whether they are to be applied by aerograph or by brush. Thereafter, they

are fired at the temperature required for their vitrification and adherence to the

porcelain.

 

Colorant fluxes: Almost all ceramic colorants are mixtures of one or more pig-ments dispersed in one or more fluxes. The amount of fluxes in the colorant gener-

ally varies from a little more than the double to four times that of the pigments.

These fluxes are highly fusible glasses of various compositions which have been reduced to fine powders. When exposed to firing temperature, their task consists  

in melting and thereby fusing the coloring particles to each other and to the por-

celain surface.

 

Colorants (or coloring agents): Generally mixtures of oxides, of which at least one

is a coloring oxide. These oxides are mixed in certain proportions, finely ground and

then calcined to obtain the desired shades.

 

Copaiba balsam: A natural rosin which, when diluted, is used as an oily medium.

 

Fashioning: Shaping of clay when it is (a) plastic (by molding, pressing, turning or

calibrating), (b) liquid (by pouring) or (c) dry (by pressing). The elimination of

water by drying causes shrinkage, since the clay particles get closer to each other.

The more water the clay paste holds, the more it will shrink when drying. Therefore,

a dry-pressed piece does not shrink or only shrinks insignificantly.

 

Firing: The paste undergoes a second shrinkage, i.e. the particles close up once

more to a point where no porosity is left. The body vitrifies, solidifies, becomes

white, ringing and translucent. The color of its translucency is the most important criterion for its visual quality.

 

Firing temperature:

• Hard-paste and new porcelain articles. Ceramic colours are fired at tempera-tures ranging from 800 to 900°C. This temperature range lies also below the

softening temperature of the glaze. The fusing properties of the colorants de-

termine their adherence to the glaze.

• Soft-paste porcelain articles. Though the firing temperature for colorants

painted before or after glazing is sufficient to soften the glaze, it is generally

accepted that all these colorants are ‘low-temperature’ ones, since they require hardly more than 800°C for being baked.

 

Flux: A white powder (mixture of silica, minium and borax) which confers more brilliance to the colors and enables a porcelain or faience object to receive a lasting decoration. Not all fluxes react in an identical manner: some of them alter the colors, especially the red shades.

 

Glass pounder: A pulverizing tool comprising a mortar and a pestle, which is very

convenient for grinding large quantities of pigment. For pole-cat dabbing a large   

surface, mix and grind small doses of pigment to make up larger quantities.

 

Hard-paste porcelain: It is based on the principle of the Meissen porcelain. In 1763, the Sèvres porcelain factory bought the secret of its composition from Pierre

Antoine Hannong. This factory owes its existence to the discovery of kaolin at

Saint-Yvieix in 1768. This clay has a high kaolin content (70%) which results in a

porcelain of ample, nourished and generous whiteness with a tendency to warm  

shades – a noble, almost austere material which is highly suitable for the artistic expression of the imperial era.

 

Lustres: Liquid products ready for use. They are of various colors (black, brown, yellow or green) and display their brilliance after being fired. As for the classic pig-ments, an elaborate color chart should be a must.

 

Mat gold: This is a black or red-brown liquid product which must be stirred for a quarter of an hour while holding the flagon in your hand. As the gold flakes tend to deposit, scrape the flagon ground thoroughly: the homogeneity of the product is essential, as the gold layer would otherwise lack uniformity and be fragile.

 

Meissen factory: From the 16th century on, Chinese porcelain has been imported

in Europe. As European ceramists admired this ‘chinaware’ for its whiteness and translucency, they tried hard to penetrate the secret of its manufacture.

The first European hard-paste porcelain is made in Germany, at Meissen, Saxony, where the alchemist Johann Friedrich Böttger discovered, in 1709, the principles of porcelain manufacture and the indispensable kaolin.

 

Oil of cloves: This oil is stronger than oil of turpentine and should therefore be handled with care. It is used for slow drying.

Oil of turpentine: It is obtained by evaporating turpentine which thickens when drying (one can make it oneself using rectified turpentine) and is used to prepare ceramic colors. This is the oldest procedure. However, nowadays essential oils are very sticky.

 

Pole-cat dabbing: A means to obtain transparent background colors using a pole-cat brush in order to highlight a motif.

 

Pole-cat dabbing of glossy areas: Coat your object with a lustre diluent, then apply your lustre using a flat brush and smoothen it with a sponge. By superposing several color shades, you can obtain interesting effects. Fire after each layer.

Before applying a protective varnish on the lustre, clean with pure turpentine: The varnish will peel off easily.

 

Porcelain: Porcelain paste is a mix of a white clay, kaolin (from a hill in SE China called Kao-ling), of feldspar which confers transparency, and of quartz which has a binding function. High-temperature vitrification of this mix results in a white paste that is hard, scratch-resistant, impermeable and translucent in thin-walled articles.

 

Sèvres blue: The term ‘Sèvres blue’ has given rise to a number of confusions and controversies. ‘Sèvres blue’ designates a transparent background color that is baked at high temperature – i.e. white-baked – after having been dabbed with a pole-cat brush on glazed hard-paste porcelain; its coloring principle is cobalt oxide. This color is referenced No. 20 in the chart for over-glaze painting. It is baked at 1,350°C under oxidizing atmosphere.

 

Soft-paste porcelain: This type of porcelain is an artificial one since its translu-cency is obtained thanks to a frit made up of a mixture of calcareous clay (marl), silica and potash. It can be shaped by molding only and is difficult to fire because   of its high degree of shrinkage. Decoration is possible after firing a lead-containing glaze according to the same procedures as those used for fine faience. There are many methods of manufacture which varied according to the manufacturers, methods that had been kept secret by porcelain makers and lost after their deaths.

Soft-paste porcelain has been made from the end of the 16th century on in Florence, at the end of the 17th century at Rouen, and during the 18th century by the factories of Saint-Cloud, Chantilly, Mennecy, Sceaux and Vincennes.

 

Turpentine: An essential oil obtained from certain conifers