On production

SHAPER

The main material for the creation of forms, which serves for the moulding of porcelain and ceramic products, is plaster binding agents G8-G12 (-8...-12). Such agents are created by thermal processing of natural gypsum-anhydrite rock CaSO4 2H2O until the formation of hemihydrate calcium sulfate. The creation of plaster forms is based on the capability of plaster binding agents to create slurry-like fluid suspension when contacted with water. This suspension quickly hardens at the open air, thanks to the ability of hemihydrate calcium sulfate to connect crystallized water and to switch into two-hydrate. The bondability is usually accompanied by the liberation heat, increase of temperature of the tempered plaster binding agents and some insufficient (below 1%) increase of its volume. Because of this increase the plastering agent will fill the smallest parts of the form, creating an incredibly precise design. Then the half-finished plaster products are being dried under 50° and then they are used for to found half-finished products.

SCULPTOR

The sculptor works with the future product on the level of the sketch and draft. Then he makes the model from the sculptural plasticine. Then he transfers in into plaster. Then he works on plaster model on his workplace, using the necessary instruments and accessories.

MOULDING

The production is characterized by the moulding of the material into plaster forms, which is considered to be one of the oldest method of porcelain creation. It is based on the ability of porous bodies to suck out water from ceramic slurry, creating a special king of hard layer on the surface, which has certain density and mechanical durability.

Compared to other methods of porcelain creation, moulding has some very powerful advantages on the stages of mass creation and specifically during formation (the possibility of creation of products of any complex configuration).

DRESSING

The moulded and dried products are being transferred to the dressing where all the stitches from the forms, roughness, which often occurs during moulding. The dressing is usually hand-made with the thin brass gauze to achieve really smooth surface. After that dust is removed with the moist sponge and the vacuum cleaner.

FIRST GLAZING

Dried and dressed products then are being processed to the first glazing. Its main objective is to create the material that won’t soak in water and possesses the necessary porosity durability, which enables the implementation of other technological operations (underglazing coloring and glaze coating).

The first glazing can be divided into the following periods:

- In the first period the products are being additionally dried, moving off various remains of liquid;

- During the second period (300°) additional sublimation of various organic admixtures (remains of natural origin), present in the mass, is implemented;

- With the increase of temperature to 450° the organic admixtures burn out;

- Between 500 and 700° hydrate water is being actively segregated, the process of hydration of clay is observed, which causes the following chemical reaction: Al2O3 2SiO2H2O → Al2O3 2SiO + 2H2O↑. Under 575° β- quartz is being transformed into α- quartz, which causes the increase of the product’s volume.

PAINTING

Manual underglazing painting of the product is being implemented by the professional painters of the highest class with the best possible underglaze paint, which sustain their structure even under the influence of high temperature. For application of the paint special kolinsky and squirrel fur brushes are being used.

After hight temperature glazing (1300°) the product are being painted with liquid (12%) gold.

GLAZING

Glazing makes the product resistive to fluids, protects it from dirt, makes it more esthetically pleasing, increases its underglaze color painting and increases their brightness.

We implement the glazing by drowning the products into the container with glazing suspension (its density is 1,30–1,32 g/cm3. The manual method hasn’t lost its universality, especially when you deal with small orders. During this difficult production process, that requires certain skills from the workers, the products are being drowned in the container with the suspension in such a way, that the layer of the glazing has the appropriate thickness and there are no fingerprints or smudges on the product.

During the high-temperature baking the glaze mass melts and a thin glass-like layer is created on the surface of the product. Its thickness varies between 0,01 and 0,03 mm.

BAKING

The baking of the product is carried out in the electrical heaters with the volume of 2,5 3. The temperature of baking usually makes 1300°.

During the baking process some physical and chemical reactions run in the porcelain mass. Thanks to them the porcelain is produced. Such reactions include: deletion of crystalline water, burning of organic admixtures and carbon, dissociation of carbonates, formation of glass-like phase and melting of glazing.

The baking involves a number of periods:

  1. Below 900-940° some insufficient caking of the crock takes place;
  2. Under 940-1040° – the temperature of the products in the oven becomes even, the carbon burns out, a small part glaze-like phase is created;
  3. Under 1040-1250° such phenomenon are observed: decomposition of ferric oxide (Fe2O3) and sulphate calcium and sodium, intensive creation of the glass-like phase, thanks to the melting of the feldspar, creation of whiskers of mullite, melting of the glazing;
  4. Under 1250-1300° the material of the product finished its formation. The porcelain ripens, the glaze spreads and melts with the material of the product. One can observe the active dissolution of amorphous silica during the melting of feldspar glass, which favors the filling pores between crystalline phases. At the same time the crystals of mullite get bigger 3Al2O3 2SiO2 in the feldspar glass and the size of the residual quartz decrease. You can see the even distribution of crystalline new formations in the material of the product. The acicular crystals of mullite interweave in the feldspar melt of really promote the mechanical durability and thermal stability of the porcelain products;
  5. The last period — cooling down (from 1300 ° to room temperature).