in the history of mankind, there are a lot of materials that accompany people almost from the dawn of civilization.The first comes to mind is a tree, but do not forget about ceramics - fired clay dishes from which you began to make from time immemorial.
Positive qualities of the material enough: ceramics durable, resistant to chemicals and high temperature influences, has full environmental safety, and to look at it all right.In addition, the tiles of fired clay does not rot and is not covered by a fungus that can be successfully used it for finishing a wide variety of technological rooms and bathrooms.
general, ceramics - are dishes or other things of clay (with mineral additives or without them), obtained with the help of forming and subsequent high temperature firing.To the appearance of such items was a beautiful, glazed them.
What materials can be used in production?
We have already said that for these purposes is used mainly clay, but there are exceptions.So, in the ceramics can go the following materials:
- Plastic base.It is just the same clay or kaolin (rock composed of kaolinite).
- materials that minimize sediment during firing, you can save the form of the product.The case is a high quality quartz sand, porcelain nekonditsiya (fight), fireclay.
- Breed, giving a dense vitreous mass during sintering.Ideal feldspar pegmatite.
- Glaze.It can be used as a material made of natural raw materials, as well as numerous analogues obtained by chemical synthesis.
Classification
So we learned that the ceramic - a specially treated clay.As the factors determining the quality of consumer products, isolated kind of ceramics, a way of decorating and shaping it.
Distinguish fine ceramics (fine grain at the turn of the crock) and gross (large grain).From subtle variations of each sign porcelain semiporcelain and faience tiles which have almost in every bathroom.Accordingly, rough ceramic (photo can be found in the article) - a pottery pots.The thing we are not too common, but known since ancient times.
properties of different types of ceramic
hallmark of porcelain is thin, dense and fine-grained white crock.The material is very poorly absorbs moisture (up 0.2%).Valuable vases or cups (very thin) can be viewed in the light.The edges of the rim (usually the bottom) because the technology does not cover the glaze firing.To produce is used primarily kaolin and feldspar.
semiporcelain - intermediate between the above porcelain and earthenware.Several rougher water absorption of 3 to 5%, most often used in the manufacture of cookware for household purposes.
As for the pottery, it is different with a thick porous crocks, which at the turn of a slightly yellowish tint.The ability to absorb water is high, in the range 9-12%.Precisely because of this, and also because of the high porosity, any ceramic articles of this type are necessarily covered by a thin layer of glaze.
Since glazing used very unstable to thermal effects, this kind of ceramic used exclusively in the production of inexpensive dishes everyday use, as well as economic capacity.For dressing take not too high-quality varieties of clay, chalk and quartz sand.Ceramic technology of this sort also allows (as a base) of broken china.Of course, before starting production it is crushed and finely rubbed.
Majolica - this is a very attractive appearance ceramics.The price on it - about a thousand rubles for above average vase.The distinguishing feature - a very porous crock, can absorb up to 15% moisture.Despite this, the products are characterized by thin shiny surfaces have a small wall thickness.The latter is due to the fact that majolica is produced by casting technology.As a rule, items are decorated with frosting, also uncommon decorative reliefs.In the production of this variety of ceramics used belozhguschihsya clay, quartz sand, chalk and smooth.
Pottery Ceramics (which has a photo in the article).Different specific shard of red-brown color (krasnozhguschiesya clay) and a very high porosity.The absorption coefficient of water - up to 18%.For painting using special paint clay, engobes.To protect them from moisture, on top of the product covered by a thin layer of colorless glaze.With regard to the scope of use, the assortment is not only decorative pots, but also quite practical utensils for household.
In addition, this category is warm ceramics.So called bricks made of baked clay rough.In the production of this type of ceramics using special foaming agents that dramatically increase the porosity of the material and therefore its insulating qualities are much better.
What is the process of production?
itself ceramics production can be divided in several following stages:
- mining and relevant training materials.
- Moulding, applying decorative patterns or functional breaching holes.
- casting, dry pressing.
- Edit, the first drying.
- high temperature treatment.
- Glazing.
- Repeated burning.
- decorative treatment (warm ceramics and analogues do not need it).
Quality indicators determined by the characteristics of the finished product appearance, full compliance with functional purpose, as well as durability.
Technology of
the main stages of production, we talked, and so now, let's discuss each of them separately.To prepare the original ceramic body, the following process steps: raw materials is thoroughly cleaned of extraneous mineral and organic impurities, crushed and milled.After that comes the turn of stirring and the addition of various additives.
Molding products Molding
made of plastic or liquid ceramic masses.In plastic molding has a number of advantages.This is primarily reflected in the fact that we can make the products of almost any shape and size.Moreover, their manufacture can accommodate even the most simple and sophisticated equipment.
As for the casting, then this applies to mass with a humidity of 34-36%.Fill produced in plaster molds.It is an indispensable method for the manufacture of ceramic products is really complex, whose shape is physically prevented from applying other methods of molding.Furthermore, since the tile is made.Pottery for it is not of the best varieties of clay (below requirements), but the thickness of the finished products must be as uniform as possible.
casting can be either manual or fully automatic.After the initial drying products are removed from the form, and then paste a variety of decorative and functional elements for the connection that uses a special glue.In the past, for this purpose used clay dough, but it provided the strength is not too high.
Drying Drying - the most important stage, since the correctness of the meeting depends on both the mechanical strength of the product and its decorative features.Of course, it is essential and proper distribution of the glaze, which determines the stability of the product to water and chemical agents.Drying - a prerequisite of the production of ceramics.For her, using conveyor, radiation and chamber dryers.The temperature throughout the process should not exceed 70-90 ° C.
exceptions are tiles.Ceramics in this case is very thick, so that in some cases the use of high temperature mode is allowed for a short time.
Firing
second most important technological step is firing ceramics.The goal - forming shard with the exact set of physico-chemical properties, binding dye composition and the glaze on the surface.Firing is important that, in the course of its proceeds are many physical and chemical processes, which determine the quality of basic consumer goods.Typically, firing is carried out in two stages, but if the surface of the glaze was applied paint, held the so-called muffle firing (third stage).
first stage is carried out at a temperature of from 900 to 1250 ° C (depending on the type and grade ceramics).The second step requires a temperature from 1020 to 1410 ° C.The latter value is used exclusively for porcelain.For other ceramics are rarely fired in this mode as a high risk of cracking.When it comes to the average red clay, the products made of it, and often does, "harness" one time, at a temperature not exceeding 960-1020 degrees Celsius.
for firing furnace can be used for ceramics in two types: periodic (horns), as well as continuous.Species past a lot, but most common tunnel and roller.
about various defects
specifics of manufacturing of ceramic products is that at different stages of production may cause a large number of a variety of defects.There crock damage, glaze or decorative coating.As for the defect crock, they most often appear at the stage of the primary molding and the initial drying.
Part of workmanship evident almost immediately, as spots or something like that only appear after firing.In connection with the "capriciousness" of the final product there is a requirement to tightly control the purity of all used in the production of tools.
description of the basic concepts
glaze - a special melts are applied to the surface of the finished product.Their thickness is 0,12-0,40 mm.Appointment glazes quite diverse.Firstly, the surface of the tile or decorative cookware coated dense layer that not only contributes to a pleasing appearance, but also significantly improves the mechanical strength.In addition, the coating provides protection against physical and chemical effects, which is especially important for household utensils.Under
decoration meant applying decorative painting or patterns.Often in industrial production using shaped dies by which mass production of one type.For drawing a pattern on the edge of the pot using the stamp roller.Accordingly, the final operation is to remove small defects, sanding the edges and legs.
Some information about glazes and paints
Glazes are divided into transparent and opaque varieties, they are fully colored and colorless.The ceramic paint is used for decoration of almost all varieties of products, in baked clay.As they are based on or metals or their oxides.When heated, they form stable compounds that are not only beautiful, but also very durable.Such ceramics, reviews of which are always beautiful, has long been a decoration in many homes of the wealthy.
Paints are divided according to the method of their application, either on a layer of glaze or under it.As can be understood, in the latter case, the ink composition is applied directly to the crock.Only then it is closed layer of glaze and the article is baked in an oven.If the composition is applied directly to the glaze layer, it is fixed a temperature not less than 600-850 ° C.
Regarding auxiliary materials, their use for the manufacture of molds for molding and sintering.
information about the manufacture of molds
To make a sufficiently strong and high-quality form, using molding plaster.It is made, finely divided powder hemihydrate calcium sulfate hydrate.Feature gypsum such that when mixed with water, it must be converted into a sufficiently plastic and elastic dough.But the main thing - the composition should fasten in well-defined terms, which guarantees really high-quality firing.If the plaster for some reason there can be used silicon carbide refractory fireclay.It is allowed to use other refractory materials.
That's what ceramics.This kind of stuff, without which it is impossible to imagine any kitchen or bathroom.However, there is another version thereof, products which can be a real decoration of any home.
Art ceramics
term "artistic" refers to the product, especially decorated with subtle relief or stucco.Of course, other differences from the usual ceramic actually not, but there are many manufacturing technology subtleties.About them we now discuss.
Initial training materials
As you know, art pottery in a little different from their "home" counterparts, but its production is necessary in these situations to the selection of raw materials.Everything is the same as in the previous case, but all operations are carried out more subtly.In addition, the use should be extremely finely divided kaolin (particle diameter less than 2 microns).
What gives?This approach allows us to obtain a much more plastic mass, and at least twice increases the strength of the dried product.Moreover, it should take only small quartz sand, as it dramatically reduces the draft of finished goods, that is very important artistic ceramics.
Drying artistic ceramics
As we have already pointed out in the first part of the article, drying - one of the most important stages.If we talk about artistic ceramics, this assertion becomes even more urgent.Please be aware that the phenomenon of shrinkage during firing of thin products occur unevenly, which can lead to big trouble, until the damage to the entire product.Therefore it is essential to choose the right heating mode, so that art pottery did not turn into a pile of shards.
If products are flat, they are strongly advised to dry only in forms.First podvyalivayut them lightly until a future ceramics will not get the required density, and only after that it can be removed, and finally dried to a moisture content of 1-2.5%.
to carry out this process in large quantities, using special conveyor dryers.In particularly difficult cases, drying is carried out in devices which operate batchwise.So do in order to thin ceramic dried up and cracked.Drying time ranges from 30 minutes to three hours.
So you know what ceramics.This is one of the oldest material ever produced by humankind.Despite its antiquity, ceramics and in great demand today.
