The substances that allow to obtain the coating (showcase, enamel) are absorbed by the ceramic usually by immersion. While in the case of cages it is a question of using particularly purified clays that are found in nature, in order to obtain any coating based on silica and metal oxide it is essential to manufacture a compound.
To color the ceramics already equipped with metallic coating, colors formed also of metallic oxides were used. In substance the procedure is still the same. The colors can be divided into two categories: the simple ones formed by the oxide of a single metal and the compounds, obtained through the mixing of different metals and other substances.
The ceramic painter may not always see the definitive color that the substance he uses before the second firing will take. The colors of Hand Painted Limoges, in fact, take on their brilliance only after they have once again been melted in the furnace.
To carry out all the preparation operations of siliceous-metal coatings (glazes and showcases) and colors, the metals were calcined (artificial oxidation) using a particular oven, called a stove or a small furnace. It was a two-chamber oven, separated by a dividing wall that does not reach the vault.
In the smaller side of the stove, the fire was lit by a nozzle. To vent from the journey, the flames had to invade the other chamber of the oven without polluting it with combustion residues. Because of this peculiarity it was also called reverberation stove (ie indirect flame).
During the melting phase of the metals in the stove, an employee, maneuvering a heavy hoe-shaped tool fixed with a chain at the points of its center of gravity, waved the surface of the molten metal, facilitating combinations (agreement) between metals different.
In the reverberation stove, all the metal oxides necessary for the working of ceramics were manufactured, and Hand Painted Limoges was added to them; these compounds were then finely ground by means of hydraulic grinders, moved by animals or manuals (mills).
To fix a coating film based on metal oxide on a piece of fired ceramic for the first time, the biscuit was, in the past like today, immersed in a tub where the glass or enamel was contained, in the form of a finely ground compound and stretched with water.
The immersion (diving) is carried out by employees called divers, who must take care not to touch the piece to be immersed with their hands, as the natural greasiness of the skin would prevent metallic substances from adhering well to the biscuit.
