you sent shade of PFM ,technician give you different color with same shade:
a- non uniform porcelin***
b- thick opaque
c- thin opaque.
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THE MANUFACTURE OF PORCELAIN:
It is in the center of Limoges and Oradour-sur-Glane (20 km) that porcelain Bernardaud is made. These two production sites produce around two million pieces a year.
THE THREE ROCKS:
The porcelain paste is composed of 50% kaolin, 25% quartz and 25% feldspar. These materials are diluted in water, crushed, mixed, sieved and filtered, to be in the form of slabs before being processed, according to manufacturing techniques, more or less liquid paste.
PASTA:
- Liquid, called slip, it is used for pouring.
- Deaerated and kneaded in the form of semi-soft dough rolls, it is used for sizing.
- In powder, obtained by atomization to obtain tiny granules, it is then compressed by isostatic pressing.
MOLDS:
The first phase of manufacturing a porcelain piece is the creation of its model. From a drawing (which represents the object made to the final scale), the modeler realizes the object in the form of a volume of plaster at the "raw size" scale, ie 14% larger than the actual size of the room; indeed, it is necessary to anticipate the withdrawal that will take the piece cooking.
The model (unique object of reference) will give birth to the mother mold also called nucleus. It is from this that the production molds will be drawn. The latter, which allow the production of porcelain pieces in series, are made of plaster, resin or steel coated with polyurethane.
CASTING is a process used for hollow parts (coffee makers, vases, tureens ...). The liquid paste is poured into plaster molds. The porosity of the plaster absorbs the water contained in the paste and fixes it against the walls of the mold. After a precise setting time, proportional to the size of the piece (it takes about thirty minutes for a tureen) the excess slip is rejected. The pieces are then removed from the mold.
CALIBRATION is a process used to manufacture round and high pieces (cups, salad bowls ...). A slab of semi-soft dough is deposited in a plaster mold itself placed on a lathe. A metal gauge lowers, crushes the dough so as to spread it against the walls of the mold and slice the excess. Calibration is called hollow when the caliber gives the inside profile of the part and calibration in the bump when it gives the external profile.
ISOSTATIC PRESSING is a process used since the 1980s to produce round and flat pieces such as plates. The pulp, in the form of granules (powder obtained by slurry spray), is compressed at a pressure of about 350 bars inside a mold of steel and polyurethane. The compacted porcelain powder forms the object. The drying time is eliminated.
DRYING:
After demolding, the parts are dried, which varies from
twenty-four hours depending on their size. During drying, the parts undergo a shrinkage of 3%.
THE GARNISSAGE consists in assembling, with the slip with a binder, the fittings such as beaks and handles on the body of the objects, but also to pierce the holes on the spouts of teapots and coffee pots.
FINISHING makes it possible to remove the seams caused by the division of the mold into several parts and to erase any other imperfection.
THE FIRST COOKING:
The parts undergo a first firing at 980 ° C for 24 hours in ovens currently operating on natural gas. This cooking, known as sharpening, hardens the parts, dehydrates them and makes them porous so that the enamel can then be fixed on the surface.
THE MESH:
When the oven is opened, brittle and porous parts are available. This porosity will allow enameling. Each piece, to have a smooth and shiny aspect, is soaked by hand in an enamel bath. Unglazed objects retain a dull appearance; they are then called biscuits. The enamel is composed of the same ingredients as those of the porcelain paste but in different proportions. Enameling is a very elaborate gesture which allows to deposit on the surface of the piece a thickness as constant as possible. The gesture is precise, fast: 1200 saucers per hour.
SECOND COOKING:
The pieces then undergo a second so-called large-firing, at 1400 ° C for twenty-four hours. The purpose of this cooking is to vitrify the dough and the enamel so as to develop the whiteness, the translucency, the sonority and the solidity of the porcelain. It is during this cooking that the room takes the main part of its withdrawal (10% to 12%) compared to the model and reaches its final size.
--------------------------------
THE MANUFACTURE OF PORCELAIN:
It is in the center of Limoges and Oradour-sur-Glane (20 km) that porcelain Bernardaud is made. These two production sites produce around two million pieces a year.
THE THREE ROCKS:
The porcelain paste is composed of 50% kaolin, 25% quartz and 25% feldspar. These materials are diluted in water, crushed, mixed, sieved and filtered, to be in the form of slabs before being processed, according to manufacturing techniques, more or less liquid paste.
PASTA:
- Liquid, called slip, it is used for pouring.
- Deaerated and kneaded in the form of semi-soft dough rolls, it is used for sizing.
- In powder, obtained by atomization to obtain tiny granules, it is then compressed by isostatic pressing.
MOLDS:
The first phase of manufacturing a porcelain piece is the creation of its model. From a drawing (which represents the object made to the final scale), the modeler realizes the object in the form of a volume of plaster at the "raw size" scale, ie 14% larger than the actual size of the room; indeed, it is necessary to anticipate the withdrawal that will take the piece cooking.
The model (unique object of reference) will give birth to the mother mold also called nucleus. It is from this that the production molds will be drawn. The latter, which allow the production of porcelain pieces in series, are made of plaster, resin or steel coated with polyurethane.
CASTING is a process used for hollow parts (coffee makers, vases, tureens ...). The liquid paste is poured into plaster molds. The porosity of the plaster absorbs the water contained in the paste and fixes it against the walls of the mold. After a precise setting time, proportional to the size of the piece (it takes about thirty minutes for a tureen) the excess slip is rejected. The pieces are then removed from the mold.
CALIBRATION is a process used to manufacture round and high pieces (cups, salad bowls ...). A slab of semi-soft dough is deposited in a plaster mold itself placed on a lathe. A metal gauge lowers, crushes the dough so as to spread it against the walls of the mold and slice the excess. Calibration is called hollow when the caliber gives the inside profile of the part and calibration in the bump when it gives the external profile.
ISOSTATIC PRESSING is a process used since the 1980s to produce round and flat pieces such as plates. The pulp, in the form of granules (powder obtained by slurry spray), is compressed at a pressure of about 350 bars inside a mold of steel and polyurethane. The compacted porcelain powder forms the object. The drying time is eliminated.
DRYING:
After demolding, the parts are dried, which varies from
twenty-four hours depending on their size. During drying, the parts undergo a shrinkage of 3%.
THE GARNISSAGE consists in assembling, with the slip with a binder, the fittings such as beaks and handles on the body of the objects, but also to pierce the holes on the spouts of teapots and coffee pots.
FINISHING makes it possible to remove the seams caused by the division of the mold into several parts and to erase any other imperfection.
THE FIRST COOKING:
The parts undergo a first firing at 980 ° C for 24 hours in ovens currently operating on natural gas. This cooking, known as sharpening, hardens the parts, dehydrates them and makes them porous so that the enamel can then be fixed on the surface.
THE MESH:
When the oven is opened, brittle and porous parts are available. This porosity will allow enameling. Each piece, to have a smooth and shiny aspect, is soaked by hand in an enamel bath. Unglazed objects retain a dull appearance; they are then called biscuits. The enamel is composed of the same ingredients as those of the porcelain paste but in different proportions. Enameling is a very elaborate gesture which allows to deposit on the surface of the piece a thickness as constant as possible. The gesture is precise, fast: 1200 saucers per hour.
SECOND COOKING:
The pieces then undergo a second so-called large-firing, at 1400 ° C for twenty-four hours. The purpose of this cooking is to vitrify the dough and the enamel so as to develop the whiteness, the translucency, the sonority and the solidity of the porcelain. It is during this cooking that the room takes the main part of its withdrawal (10% to 12%) compared to the model and reaches its final size.
THE CHOISING:
This is the last stage of white manufacturing. All parts of the production are checked one by one and chosen according to their quality level. Despite numerous interim controls, over 25% of production is discarded at the time of selection. The most common defects are stains, cracks, lack of enamel, deformations and cracks. Some defects can be repaired.
THE DECORATION:
Depending on the style of the collection, the setting of the decor is more or less complex. Some valuable pieces are hand-painted and craftsmen demonstrate exceptional dexterity using a wide variety of brushes.
In the majority of cases, a decoration to the sheet (principle of decal) is affixed by hand on the white porcelain. It is soaked in water so as to detach the pattern from its paper support and applied to the piece. The decoration with the sheet is manufactured by various printing processes, originally lithography, currently screen printing. The Manufacture Bernardaud is one of the few in Limoges to own a printing press.
Nets and trimmings (handles, beaks ...) are all hand painted. These decorating techniques are the most common. In the case of special orders, one may resort to more specific techniques such as incrustation or laying gold relief.
INCRUSTATION is a process of decoration by etching with acid. The piece is traced: the decor to the sheet is printed not in color but in protective varnish. This same varnish, also called bitumen of Judea, is applied with the brush on the rest of the piece except for the motif to be engraved. The piece is then immersed in a bath of hydrofluoric acid which "attacks" the enamel, thus forming the hollows of the pattern. It is then rinsed with oil, laundry and water, before being successively decorated with two layers of gold (shiny then matte) or brilliant platinum, requiring two firings.
The laying of gold relief is a technique of decoration that consists of brushing gold patterns in thickness, using a special paste. After cooking, the decor is sprinkled with fine gold before being cooked again.
SANDBLASTING:
For pieces with gold, the last operation is sanding. Indeed, when cooked, gold has a matte appearance. Sandblasted, that is to say, rubbed with a cloth and sand, it takes all its brilliance.
QUALITY CONTROL:
Before leaving for its final destination, each object is carefully checked after each operation, in order to offer Bernardaud points of sale in the world a product of very high quality.
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