Porcelain "on the bones": a product shortage
word "bone" in the title of the finest porcelain - not a metaphor, as a literal reference to the composition of the raw material.Plain porcelain mass consists of kaolin - white clay and other clay materials giving during firing white, as well as quartz and feldspar.In England in the middle of the XVIII century began to add to the composition, and even bone ash - contained therein calcium phosphate attached and utensils such an incredible whiteness.
the Imperial Porcelain Factory (in Soviet times it was called the Lomonosov) Bone China launched in the sixties of the XX century.Paradoxically, the fact is that the reason why the plant has mastered this technology was not ambitious desire to produce elite "royal" dish, but ... shortage
Since 1965, the plant experienced serious difficulties with the arrival of kaolin - white clay is widely used in paper, perfumery and military industry.But there were a lot of waste bones.Therefore, the plant director Alexander Sokolov has set production laboratory LPF task: to develop a structure of weight for bone china.
composition of raw materials was adjusted by trial and error (foreign colleagues were in no hurry to share trade secrets).As a result, it turned out, for example, that the birds gave Bone china unnecessary magenta tone.
a result stopped on the tibia cattle.Moreover, that there was no shortage of raw materials.Manufacture of buttons stamped from defatted bones buttons to pillowcases and military uniforms - and the waste went to the porcelain factory where burn through.
Mass for the manufacture of bone china only 55% consisted of a conventional kaolin clay, feldspar and quartz - the rest is accounted for bone ash.
In 1968, the factory was running a workshop for the production of bone china.In contrast to the English porcelain, which was thick enough to LPF decided to release a thin-walled porcelain.And at first, even "overdone": the first cups were so thin and unreal light that consumers began to complain of a feeling of "plastic".Therefore, the thickness of the crock decided to increase by 0.3 mm.
Birth "thin stuff»
from bone china cups, and many other porcelain products, produced by casting.For this form of molded gypsum is filled to the brim with liquid porcelain mixture resembling cream - slip.Gypsum begins to "select" the slip at the moisture - and the result on the inner walls of the mold gradually increases porcelain "crust."When she dials the desired thickness - excess slurry is removed from the mold.Then dried up, "crock" (so called unfired porcelain) begins to lag behind the walls of the mold - and recovered.
In the production of porcelain figurines details "gaining thickness" for quite some time - a few hours.With thin-walled cups, everything happens much faster - at the Imperial Porcelain Factory bone porcelain mixture is poured into molds by only two minutes.
Olive happens automatically - the forms are moving in a circle, from the dispenser automatically pours the right amount of slip, and then vacuum suction "takes" too much.
handles cups, teapots, sugar bowls are cast separately and then "glued" manually.As the adhesive performs all the same mixture of porcelain, only thicker.
flat products (saucers, plates) are made by stamping.Porcelain cake mix for these products are doing very tight, it reminds dough, roll into a "sausage."Cut a piece of "sausage" is placed on a plaster mold, falls on top of him rotating forming roller (for each model of your video).Surpluses are cut automatically, but sanded the edges and make the surface absolutely flat - the problem of so-called "opravschits" working by hand.
Sponge, brush, frosted glass, Abrasive - opravschits tools have a simple but effective and time-tested.These headers porcelain fall after drying.
Bone china is fired twice.And for the first firing temperature is very high - 1250 - 1280 degrees, which is much higher than that of conventional porcelain.At this temperature, the mixture is completely porcelain "baked" and acquires the necessary strength.The oven holds utensils for 12 hours.And by the way, is reduced in size by about 13%.
But not yet shine.Luster appears after the porcelain is covered with a glaze.It is composed of the same materials as porcelain, but in a different percentage, moreover, it is added marble and dolomite.During firing the glaze melts, forming a glossy shiny surface.
icing on the bone china is applied with a spray gun - first one and then the other.And to be able to control the density and thickness of the layer, the glaze is colored magenta.Therefore, going into the oven for the final baking, cups and saucers have a bright purple color.At high temperatures, burns and pigment is white porcelain.
second firing also lasts 12 hours when the temperature at this time below - 1050-1150 ° C.
way, the firing temperature of bone china was the reason that the Lomonosov Porcelain Factory was able to maintain a monopoly on the production of Russian bone china.
Among Soviet factories had been taken to keep the technology secret, so in the early 70's technology and equipment design have been "donated" the Republic of Bulgaria, which then launches new porcelain production.And in 1982, the technology was transferred to a ceramic factory in Kaunas, Lithuania.But Russian plants did not dare to take on the production of bone china.The catch turned out that this porcelain is very sensitive to the temperature of the firing - and the deviation from the set temperature parameters literally 10 degrees transforms dishes into marriage.Thus, when it comes to temperatures of a thousand degrees, even the error of measuring devices can exceed these same 10 degrees.LPF and remains the only producer of "royal porcelain" throughout the country.
How does pattern
Pure white, unpainted porcelain which is not touched by the hand of the artist, the experts called "linen".But before they get on the shelves of branded stores, utensils should be decorated with a pattern.
painting on porcelain is underglaze, glaze, and combined, combining both techniques.In such cases, the pattern is applied in two stages.An example of a combination of painting can serve as a well-known pattern, "Cobalt net" which has become a kind of "calling card" of the plant.
Cobalt drawing - blue line - is applied to the porcelain before the glaze coating products - the high-temperature firing decoration "fused" in a transparent glaze tightly.Cobalt, before firing having a dull faded black color when heated magically changed, and depending on the concentration pattern becomes pale blue or dark-blue.By the way, all the colors used in underglaze painting behave in the same way - the color "seen" during thermal exposure, and when applied to the figure they look pale - shades of black, gray, brown.And artists working with multiple colors at once, have a hard time: they constantly have to "bear in mind" the future picture.
Figure often applied by hand, but sometimes the job can be made easier.On the Imperial Porcelain Factory, for example, we developed special forms for cookware, which will be adorned with "cobalt grid": on the sides of the crock "is depicted by a" thin, barely visible grooves - a kind of circuit, which must be manually "circle" lines of cobalt.
Cobalt pattern may popadalt on the product and using decals - a thin film-like decal is printed on cobalt pattern.
decal form corresponds exactly to the shape of dishes - each model is its own.When heated, the film is burned, and pattern - imprinted in the surface of the product.
application underglaze drawing takes place after the products have passed the first firing - before glazing.After the second firing such dishes sometimes looks very strange - it has applied the first part of the painting, while the second is still waiting in the wings.But you can imagine, it would look like AK.
painting in gold - it is overglaze painting.Then dishes will be another firing, but at lower temperatures - only to consolidate the pattern.It allows to use when painting the precious metals, as well as many paints that can not stand "four-digit" temperatures.Golden stars on proprietary pattern can be applied manually with a brush - or by means of a miniature of the die.