الخزف ( السيراميك ) ٢ _ a , من كتاب تكنولوجيا التصوير , د.م محمد حماد

The oxidizer, and some in which the manufactures are exposed to a direct flame, and some of them are satisfied inside the manufactures that are protected by cans that take the place of the box.

Furnaces differ in terms of flame directions, so we find some that have a flame that rises vertically to the chimney, and some that have a flame that is reflected inside the oven and then escalates vertically to the chimney, and there is another type known as a mobile flame. Furnaces also differ in their shapes and sizes, as they are square, round, and with adjoining chambers, and they also differ according to the method of burning..and they can be divided in this respect as follows:

(1) Wood-fired kilns, which are the best kilns for producing artistic pottery.

The flames emanating from the burning of wood help to give the natural artistic touches to the burnt works (b) the peers of diesel and diesel, and they help to give the multi-oxidized atmosphere

Or abbreviated (c) electric furnaces, and they are distinguished by the cleanliness of the place, the cleanliness of the work, and confirmation of the burning result as much as possible, and therefore they can be used inside inhabited places such as residences, schools and research centers.

E - Stages of work:

After preparing the clay and shaping it in the required manner, it is left to dry away from air currents and direct heat such as the sun, so as not to be exposed to damage, warping and cracking. And after it is completely dry, the first fire is burned at a temperature suitable for the material from which the works are made. Silt is not exposed to a high degree; As it bends and begins to melt at a temperature of about 5800 C, while the clay loaded with iron oxide can bear the degree of 5900 C, while the Aswan clay can bear the degree of 1000 C, and the white clays such as kaolin in which aluminium is available can reach a temperature of up to 1100 C.

And since the basic material in the brick is aluminosilicate, it is affected by heat when it rises to 52000 degrees Celsius. Therefore, when manufacturing it, some raw materials are added that are affected by a lower temperature than it, such as feldspar powder, bone powder, or some impurities.. In general, the appropriate degree for fire is between 51000-800 degrees Celsius It depends, of course, on the material that makes up the clay.. And it is the artist’s experience that makes it easier for him to adjust it, and we note that the duration of the first fire for drying in a regular oven is about 4 hours, and the burning continues for the second period for 4 hours as well, with an increase in the temperature of the oven until it reaches the required degree for burning artifacts. After the fire is complete, the artefacts are cleaned after being removed from the oven so that they do not have dust or impurities on them, then they are painted and decorated with the aforementioned colored glass materials according to the required design. After it is completely dry, it is burnt again at the appropriate temperature, then the oven is left to cool down gradually until it is completely cold, and it is opened to show the works with good luck.
(Maroon Rose) dark blue, dark green, blackish brown, maroon pink, white, turquoise blue, red-brown, violet, green, light pink, light yellow, light green, black

Heat Resistant Porcelain Colors:

Porcelain can be painted with colors that resist heat and chemical reactions, and these colors can be obtained in the form of a powder, or mixed into a paste to be used in paint by brush directly or by silk-screen printing. The most important of these colors are:

These colors have the ability to mix and have 16 degrees of shade, and they can be mixed with any degree except for Maroon Rose, and this feature helps to obtain a very large number of colors during the industry. These colors are used by brush directly, or of course by net or silk screen, or of course on stone, or by spraying with an airbrush. However, it should be noted that the color deposited is not very thin, and in the case of screen printing, nylon fabric number 90-100 is used.

The types of ceramics prepared with refractory colors are fired in kilns with a temperature of 51000-51100 Celsius. The optimal temperature depends on the time of firing and on the desired color.. It can be determined by training to produce good models that are resistant to heat, chemical reactions, friction and pressure.

Gilding in ceramics:

It is known that the Arabs worked gilded units on glass, and they were ironed in special ovens, like in the manufacture of pottery.. Gold was mainly used in gilding. But the difficulty in this method is that a thick layer of gold must be made, which is then treated with steel after placing it in the furnace. This method was very expensive. Then he invented liquid gold around the year 1830, but it also had several defects, then this method changed after that in the year 1879 with Frankfurt gold. In the year 1880, wear-resistant gold entered the markets, and since then it has spread in the markets. Then the Frankfurt gold industry improved and the amount of its use in the industry increased widely.. Within about a century, lustrous preparations were developed for the decoration of ceramics, glass and enamel. This was followed by new metallic preparations of silver and platinum, and preparations for electromechanics.

The types of glossy gilding preparations are:

(1) Shiny gold, which is in the form of liquid and paste, and is pure gold. (b) The bright lemon gold in the form of a liquid and paste, and it is made of gold to which silver is added to give it a greenish color.
(c) Shiny platinum, which is in the form of liquid and paste. It is platinum compounded with gold

You will notice that liquid preparations are suitable for using a brush, making incisions, printing and spraying. As for paste-shaped preparations, they are suitable for making decorations by imprinting.

And for dilution, some diluted oils are added because the preparations evaporate during use, and it depends on the method of decoration used and the degree of viscosity of the preparation that can be controlled by adding oil. The average amount of diluent added ranges from 20 to 25% for the precious metal preparation used. For diluted oils, brush, spray gun, silk screen printing, or stamping are used.

And the trained person can control the thickness of the greased layer, and he can change it as he pleases, and he tries as much as possible to make it thin, but within limits that he cannot exceed. On the other hand, the paint should not be thick, because the shiny layer in this case cracks and separates from the painted surface when placed in the fire.. But there is another problem that results from the thinness of the painted layer, as the gilded edges become indistinguishable.

Different ways of coloring:

(1) Stamping: It is noted in this method that the oils with which it is stamped are often added to liquid preparations before being used by means of the rubber stamp with which it is printed. This method of decoration has its own cosmetics. (b) Printing by means of mechanical processes: it is at the level of mass production and not for works of art in which manual skill and artistic character are valued

personal. (c) Printing with a machine to make letters with paint: a rotating machine is used in this process, with which molten gold or a liquid preparation is sprayed on

surface to be gilded

(d) The printing machine: a thick preparation is used in it, which is placed on the surface to be painted by means of a rubber roller, and it has the required drawings, and its surface is provided with paint to carry it to the surface on which it is intended to be painted. Seals made of rubber.

(E) Printing by spraying or spraying: This method is used for wide surfaces or complete decoration. We note that the air pressure in the atomizer is from 2 to atmosphere, the diameter of the hole is from 2. to 4. . millimeter . In this case, there must be a special device to recover the exhaust metal.
(f) Screen printing: This technical method, which we will explain in Chapter Nine (engraving), is now widely used in painting on ceramics, and it requires special preparations, but it is available at hand in the present era. Fine nylon gauze is usually used in it, and sometimes a cloth of hard wire is used for it. The same width of the openings.In many cases, especially in the decoration of glass, the printing is directly on the surface to be decorated, and the printing can also be by means of printing paper for indirect printing, by means of special preparations.

In all these cases, you must note that the drying should be in completely dust-free rooms. The fire rooms are also an oven in the form of a box with a door in the front, and the fire is in it by electricity. The time required for heating is from 2 to 6 hours.. This depends on the capacity of the oven, if it is / or 1 cubic meter, and it also depends on the temperature. The oven must have a constant renewal of air, and a continuous discharge of smoke

As for the degree of combustion required for glossy preparations, it varies according to the ceramic material used, and the degree of ductility of the material such as glass or something else. Here we see a list of the necessary temperatures.

Chinese (porcelain)

ceramic pottery

5700 about

about

About 5600 m - 5650 m About 500 m - 580 m

About 700 m - 800 m

enamel glass