DIY pottery. Pottery kiln - types and preferences

Transforming clay into the most ordinary kitchen pot is an amazing process.

In fact, compare a piece of clay with a clay shard. Clay is crumbly and loose. The shard is dense and strong. The clay gets wet from the water and turns into dough. The shard does not change due to water. The clay can be given any shape: it can be sculpted, rolled into plates, twisted into ropes. The shape of a shard cannot be changed unless it is broken into pieces.

To understand all this, let's try to make a clay pot ourselves. It's not that difficult at all. They say that “it’s not the gods who burn the pots.”

To fashion a pot out of clay, you first need to prepare clay dough - mix clay with water. But we will not take anything on faith, but ask: is it possible to do without water?

It turns out that it is possible. A press was invented that molds clay products - tiles, dishes, floor tiles - without a single drop of water. Dry clay is placed in a steel mold and pressed with a steel die. True, this requires enormous pressure - two hundred atmospheres. Do you know what this means? To squeeze a book with such force, you would have to put four freight cars loaded to the top on top of it, one above the other. But you and I don’t have such a press. Of course, it is impossible to squeeze clay with such force with your hands.

Just as oil reduces friction in machines, water in clay dough reduces friction between individual clay particles. But molding consists of moving particles, forcing them to be positioned the way we want. And besides, the water does not allow them to crumble, but holds them one next to the other.

But this is not enough: by molding a clay product under pressure, we not only give it shape, but also compress it, making it denser. And water helps us with this.

If a product made from clay dough is dried, the water will evaporate. And because the clay particles come closer together, the product becomes denser. A clay brick can shorten by a whole quarter when it dries out.

The only bad thing is that, as the clay product dries out, it very often cracks, like the bottom of a dried-up puddle. You've probably seen cracks in clay soil that has dried out after rain. They resemble those huge chasms that form on the surface of the earth during an earthquake.

Dried cracked clay

To prevent the clay from cracking when drying, sand is added to it. Grains of sand, sitting here and there in the clay, hold it together like a strong frame or skeleton, and prevent it from shrinking too much.

After we have understood all this, we can get to work. Let's take out a piece of clay, add water to it - about a third - and knead it. If you add more water, the dough will get dirty on your hands; if less, it will crumble.

Add some very fine sand to the dough. Knead well so that the sand is not visible. All that remains is to fashion the pot.

The dough may not be successful the first time - after all, there are different types of clay. Some clays require more sand, others less. The composition of the test is best determined by experience. If one pot doesn't work out, we'll make another until we get what we need.

Here the pot is sculpted. But how wrong and unsightly he is! If you look at it from above, you can see that it is not round, but elongated, like the face of a person with a swollen cheek.

And it would be difficult to do better. After all, it is not at all easy to do by eye so that the walls everywhere are equally spaced from the middle. It's like drawing a circle without a compass.

Potters form pots on a special machine. A pottery machine is a round board that rotates on an axis. It is driven by the foot.

The potter places a piece of dough in the middle of the board and, pressing his thumb inside the dough, holds it with his other fingers on the outside. While rotating, the dough rubs against the potter's fingers and is leveled into a round wall. It's the same as drawing a circle by holding the compass steady and rotating the paper. The compass is the stationary hand of the potter, and the rotating paper is the round board of the potter's press.

Whether it’s good or bad, the pot is sculpted. Let's put it on a shelf somewhere to dry for two days.

When it dries, you will need to burn it. If the pot is not burned, it will not be possible to pour water into it. After all, water will turn unfired clay into dough again. It would be nice to have a pot that would get soggy from the water and crumble into mush!

Place the pot in the oven over hot coals.

Something bad can happen here. If the pot is not dried well, it will fall apart.

The heat will turn the water remaining in the clay into steam. And since steam takes up many times more space than water, it will tear the walls of the pot and escape into the wild. To prevent this from happening, the pot must be well dried.

While it’s standing in the oven, we’ll figure out why we hid it there.

During firing, clay particles are welded and fused together. This means that the burnt shard no longer consists of individual particles that can be easily moved by moistening with water, but of a continuous, sponge-like mass. That is why you can no longer make dough from a shard.

Pottery kiln

You couldn’t help but notice the new fashion trend of our days - “handmade”. Do you think that the popularity of this type of activity is for no reason, and that people do it for fun? Of course not. There are many reasons for such an interesting and useful activity. You can consider this using the example of making dishes with your own hands. In this article we will look at options for making ceramic dishes.

Making dishes with your own hands

First we need to decide on the material from which we will make something. The most common raw material for making dishes with your own hands is clay. Let's delve into all the intricacies of this matter and look at a few examples.

Becoming a master is easier than you might think

Clay dishes are a combination of beauty and practicality. Such equipment is the most ancient and had no alternatives for a long time. In ancient times, people did not use firing to create dishes, but then they learned to prepare ceramics.

Clay dishes cope with the preparation of a variety of dishes and are an integral assistant to the housewife. She:

• durable;
• heat resistant;
• environmentally friendly;
• beautiful.

Important! Some believe that the material used to make items draws out bad energy through a combination of water, earth, air and sun.

And doing something with your own hands is the most pleasant thing, because you put your soul into such things, and questions like: “did the manufacturer do his job well?” will, of course, not occur. So is it difficult to make dishes from clay? No, you will soon see for yourself.

Making a clay plate with your own hands

Now we will consider in order all the nuances of making dishes from clay.

Preparation of material

The first step is to prepare the material with which we are going to work. Simply follow these tips:

1. You need to find clay, and in order to determine whether it is suitable for making dishes: you need to take a small lump of slightly damp clay, roll it into a rope between your palms and bend it in half. If no cracks appear at the bend, then you can safely deal with such material.
2. Place the required amount of clay in some deep container and fill it with water to the top.
3. Don’t be afraid to go overboard with the amount of prepared material. Nobody forbids you to use the surplus in the next sculpting and make something else out of clay.

Clay elutriation

Elutriation will allow the clay to become more plastic, fatter and cleaner.

Important! Most often, elutriation is carried out with clay that contains sand in large quantities, which is why it becomes less plastic.

What exactly needs to be done:

1. We take a deep dish, put clay in it and fill it with water in a ratio of 1 to 3, leaving the material to moisten all night.

Important! The water should completely cover the clay in the container.

1. In the morning, bring the mixture to a homogeneous consistency. Let the solution sit for several days. Further work can begin only when the water becomes lighter.
2. Drain the water through the rubber hose.
3. Scoop out the clay down to the very bottom layer. There is no need to touch the layer itself, because only stones and sand will remain there. Pour the mixture into a wooden box and leave it in the sun to evaporate unnecessary moisture.
4. When most of the water has evaporated, you can start mixing the clay. The material should dry until it takes on the consistency of dough and begins to stick to your hands. Now the finished clay, which should be covered with polyethylene, remains to wait for modeling.

Important! Be sure to remove the air before sculpting. To do this, knead the dough with your hands. You should add a little water if the material is very hard.

Let's move on to the next stage, in which you will make ceramic dishes.

Making pottery

Objects can be made from clay strands or flat pieces. We recommend making dishes using the first method. We take a rolling pin and a piece of clay, roll it out and give it any desired shape. In this way you can easily make bowls or shallow plates.

In order to make a pot or vase from the material, you should adhere to a different technology:

1. We make the bottom for our dishes as described above.

Important! The bottom should not be too thin. The optimal thickness should be approximately 2 cm.

1. Cut the clay into pieces and use a rolling pin to make ropes out of them.
2. We place the end of the tourniquet on the bottom and press firmly so that it is secured to the bottom.
3. We place the rolled strands on top of each other, pressing the new layers.
4. Moisten the strands with a small amount of water if the material hardens.

Important! You can create fancy vessels of various shapes using these sculpting methods.

Drying

There's no need to rush. Rushing can cause cracks and wrinkles on the surface of the ware, which can lead to defects during firing. Making dishes from clay is not difficult, but you can’t do it without patience. Just follow all the deadlines and the result will please you.

The dishes should be dried bottom up in a draft-free room for at least two days, then transfer the product to a warm oven and dry until the moisture has completely evaporated.

Important! The pot may burst during firing if you do not completely remove the moisture.

Firing the product

There are special stoves for various purposes that you can purchase and install at home. But we were talking about an easy and accessible method, so we will do the firing on a regular fire:

1. We line the dishes with wood and set them on fire.
2. We wait eight hours minimum.

Important! The longer you keep the product in the fire, the stronger it will be.

If you did everything correctly, then at the end you will have an excellent ceramic product that is highly durable. It is worth noting that the manufacturing method does not require any special costs. Making pottery from clay is not difficult, and constant practice will make you a master potter.

Five reasons to start sculpting

Still don't see a reason to get into crafts? You'll soon change your mind!

Reason #1: uniqueness

Only you can decide exactly how your clay plate will look. Imagine what a surprise your guests will be when, instead of buying a set from Posuda Center, you get a set that you made yourself. Such things will instantly attract attention.

Reason #2: environmental friendliness

Did you know that harmful materials are still used in the production of tableware? The glaze made from the same lead gives the product an attractive, beautiful shine. There is not much lead there, but using such utensils is more expensive.

Moreover, this kind of product is even prohibited in some countries. Better think 100 times before buying a cheap and bright cup or bowl.

Important! Do not forget that there are natural colored clays: blue, green, black.

Reason #3: replenishment

Your set will not suffer from a broken mug or plate, because you can always restore the loss. With the arrival of a new friend or family member, there is nothing stopping you from adding a new item to your collection. If necessary, you can absolutely always do something new and useful. And when looking through your vacation photos, you might see a beautiful vase in a gift shop and easily recreate it at home. Great, right?

Reason #4: quality

There are often cases of online purchases that disappoint you immediately after opening the package. The beautiful design began to peel off from the mug after washing, and the plate was scratched by cutlery.

When making dishes yourself, especially when processing them in a ceramic workshop under the watchful eye of a specialist, such disappointments are completely eliminated. You will be taught how to handle clay correctly, and all the nuances of manufacturing technology will be explained step by step, which will help make your dishes of the highest quality and practical.

Important! Such products will not be damaged by the dishwasher or microwave. Over the years of use, you will not see any cracks or peeling paint.

Reason No. 5: saving the family budget

Even if you have made only a couple of mugs, then this knowledge will be enough for you to competently understand dishes, materials and glazes. If some seller begins to assure you of the enormous cost of a coffee pair made of blue clay, then you can safely fight back and will not allow yourself to be deceived.

Video material

It’s hard to even imagine how diverse ceramics are. Let's try to list only the most important types of ceramics. Based on their intended purpose, ceramics are usually divided into construction, household and technical.

Construction ceramics: bricks, tiles, pipes, different types of facing tiles for exterior and interior walls of buildings, tiles and slabs for floors, sanitary products (sinks, bathtubs, toilets, cisterns for them, etc.).

Household ceramics: dishes, art products.

Technical ceramics: a wide variety of products for mechanical engineering, rocket science, radio electronics, electrical engineering and other industries.

However, with all the diversity, they distinguish between dense and porous. It does not matter what raw materials the product is made from, what color its shard is, or how the surface is finished. Dense ceramics include: unglazed porcelain (“porcelain biscuit”), as well as glazed; faience Representatives of porous ceramics are: majolica, terracotta, fireclay.

However, do-it-yourselfers are mainly interested in technology for making ceramics, products from which they can make themselves. These are majolica and terracotta. These are what we will talk about below.

Modeling, finishing, casting...

A pot is formed from clay in different ways. Ancient potters took a bag of wet sand, gave the bag the shape of a future pot, and then covered it on all sides with wet plastic clay, leveled the surface and sometimes applied a pattern in the form of stripes and spirals onto the soft clay with a wooden stick. When the clay dried, the sand in the bag also dried. Then the sand was poured out, the freed bag was easily taken out, and the clay pot was fired over a fire...

Then they came up with the potter's wheel. The ceramic products made on it have the obligatory shape of bodies of rotation, at least initially. They also sculpted images of animals and people from clay. These figurines were not as symmetrical as pottery.

But large stucco products did not work out. The fact is that they could not be made hollow, and therefore they inevitably turned out to be “thick-walled”; as a result, they usually cracked or were severely deformed during drying and firing.

It is not known who was the first to notice that if clay, heavily diluted with water, in the form of a creamy mass (slip) is poured into a vessel with porous walls that absorb water, then a crust of clay will form on the walls of the vessel. The longer the slip is in such a vessel, the thicker the crust forms. If you then pour out the excess slip and let the resulting crust dry, it can be removed from the vessel. And you will get a casting, the outer surface of which will be a copy of the inner surface of the vessel.

This observation formed the basis of the so-called drain method of forming ceramic products of complex shapes, for example, figurines, vases, tiles, toilets, sinks. Many unique works of art were obtained using the drain method.

Below we will get acquainted in detail with exactly this method of making majolica, that is, products made of colored baked clay with a large-porous shard, coated with enamel.

The sequence of operations for the drain method of forming ceramic products is as follows:

All solid components of the raw mixture are prepared, and it is best to grind them to facilitate subsequent grinding; carry out wet grinding, this is a very important operation on which the quality of future products depends (in addition to clay and all additives, water is also poured into the mill during such grinding);

The resulting slip is poured into pre-prepared gypsum split molds and kept in them until the required wall thickness of the products is achieved;

The “extra” slip is drained from the molds, and the molds with the products are left for initial drying - drying;

Carefully separate the molds and remove the products from them;

The products and molds are dried (after drying, the latter are reused for molding);

Dry products are covered with a layer of glaze;

Glazed products are fired in a kiln and cooled.

There are no details in the general scheme for obtaining majolica using the drain method presented here. But it is in these details that the very secrets and tricks that are called the secret of pottery are contained. But more on secrets a little later. I want to immediately warn those who decide to try their hand at this wonderful craft that they cannot do without a mill and a furnace. Please take this into account.

Clay differs from clay

Clays are different. Geologists and technologists distinguish many types of clays. For us, information about the clays with which we have to work is important.

Simply, clays are sedimentary rocks consisting primarily of clay minerals (kaolinite, montmorillonite, halloysite, etc.) and a certain amount of impurities, which have the ability to soak and swell in water, thereby forming a plastic mass. These rocks are usually reddish-brown or yellow-brown in color.

Kaolins are sedimentary rocks of clay minerals consisting primarily of kaolinite or its varieties. (Kaolinite is a mineral of the subclass of layered silicates, Al 4 (OH) 8 - Ed.)

Bentonites are sedimentary rocks, but they consist of minerals of the montmorillonite group. These minerals have a layered crystalline structure like graphite or talc, that is, they consist of the finest scales that can slide over each other under mechanical influence. This is why these minerals feel greasy to the touch. In addition, between the scales there are cavities into which water molecules easily penetrate. Due to this, bentonite clays swell strongly in water and form a plastic dough.

With all the diversity of clay minerals, they have a common feature: they were formed during the chemical destruction of other minerals and therefore the sizes of their crystals are very small - only 1...5 microns in diameter.

In addition to clay minerals, all clays contain one or another amount of impurities that greatly affect the properties of clays, and therefore the composition and amount of impurities must be taken into account when working with clay. Let's get acquainted with the main impurities contained in clays.

Quartz is one of the most common minerals on Earth, consisting of only silicon dioxide - silica (Si0 2).

Feldspar is a fairly common mineral, which, along with silica, necessarily contains alumina - aluminum oxide (Al 2 0 3), as well as the oxide of one of the metals such as sodium, potassium, calcium (most often these three).

Mica is a mineral familiar to everyone, characterized by the fact that it very easily splits into the thinnest transparent plates. Mica contains silica, alumina and (often) compounds of iron, sodium, and magnesium.

Most often, these impurity minerals make up the sand present in the clay. Less commonly found in clay are grains of limestone, gypsum, and other rocks and minerals.

Different minerals have different effects on the properties of clay. Thus, quartz reduces its plasticity, but increases the strength of the shard after firing. Feldspars reduce the sintering temperature. But limestone grains can be both beneficial and harmful, depending on their size. If these grains are large (up to 2 mm in diameter), then they are harmful to ceramics. The fact is that when fired, limestone turns into calcium oxide (CaO), that is, into the very lime that we call boiling water. Lime grains in a ready-made shard will definitely “pull” water vapor from the air. At the same time, the lime will begin to “quench”, greatly increasing in volume. In the end, such expansion of a grain of sand will lead to the destruction of the product, which will certainly crack. If the same impurities are in the clay in the form of a fine powder, and evenly distributed in it, there will be no harm from them. Sometimes, on the contrary, it is useful to add a certain amount of finely ground limestone to the clay. For what? We will talk about this later.

Impurities in clays are found not only in the form of grains. Some minerals that are soluble in water seem to permeate the clay. These are compounds of iron, manganese, sulfur and a number of other elements. They are what most often gives clay its color. To verify this, do a simple experiment. Place a pinch of ordinary brown clay in a glass and fill it with vinegar. Stir the contents, and then rinse carefully with water so as not to drain the sediment. You will see that a white or light gray sediment remains in the glass, and all the brown color has transferred to the water. This happened because the impurities that colored the clay dissolved in the acid and were “washed off” with water.

What you need to know about clay

The properties of clays are very diverse and numerous. Therefore, we will dwell only on the properties that are especially important for potters, so that they can choose the right clay, and most importantly, prepare it for work.

Among the properties of clay, its sandiness, which characterizes the content of sand particles in the clay, is somewhat distinguished. To determine the sand content of clay, you will need a sieve with a mesh size of 0.14 mm. Take 100 g of dried clay and soak it in a large amount of water until completely soaked. Then the resulting wet mass is placed on a sieve and washed with water until the turbidity in the drain completely disappears (to “clean water”). After this, the substance remaining on the sieve, and this will be the sand contained in the clay, is transferred to a metal plate and dried on the stove or in the oven. Next, the sand is weighed with an accuracy of 0.1 g. The mass of sand in grams will be equal to the sand content of the clay.

The remaining properties of clay, the knowledge of which is necessary for the potter, are usually divided into water and fire.

Water properties

Plasticity is the amount of water that must be added to the clay to form a plastic dough. This amount of water is determined experimentally.

Take 100 g of dry clay, ground in a mortar to a fine powder, and add 5 g of water to it. Knead the dough, roll it into a ball, place the latter on a flat surface, for example, on a table, and roll it into a “sausage” cylinder with the palm of your hand (Fig. 1). If the “sausage” begins to disintegrate after some time, there is not enough water. Then the experiment is repeated, adding a larger amount of water to the clay, for example, 10 g. But you cannot add water to the already prepared dough, you will have to knead the dough again. If this time the cylinder falls apart, it means there is still not enough water. Then you need to increase the amount of water by another 5 g. In a word, this procedure is repeated until the clay “sausage” either stops cracking (which means the rolling limit has been reached), or begins to simply spread over the surface, which indicates that the yield point has been reached.

The difference between the moisture content of clay at the yield point and the moisture content of the same clay at the rolling limit is called the plasticity number. The value of this number is used to judge the plasticity of the clay. Let me also remind you that relative humidity is characterized by the ratio of the mass of liquid contained in a wet substance to the mass of this wet substance. Humidity is expressed as a percentage. So, clay is considered low plasticity if its plasticity number is less than 7%; for plastic clay this number is 7...15%; for highly plastic clay it is more than 15%. Knowledge of the plasticity of clay is very important when formulating a ceramic mass, as well as for assigning a drying regime for products.

The plasticity of clay can be changed to some extent by introducing additives.

Air shrinkage- reduction in the volume of clay as it dries. When water is removed from clay, the mineral particles that make up the clay move closer together, which causes shrinkage. This is also a very important characteristic that will be needed, for example, to determine the dimensions of a raw product. Air shrinkage is determined as follows. Having prepared and kneaded a certain amount of clay dough, the moisture content of which corresponds to the limit of plasticity, it is wrapped in a slightly moistened piece of canvas and placed on a flat board. Next, the dough is “tapped” with a wooden mallet. This technique, called punching, produces a dough without air bubbles or voids. Then, without removing the clay from the canvas, they give it the shape of an even layer 10 mm thick. After this, use a sharp knife to cut the clay (without canvas, of course) into squares with a side of 50 mm. In this case, use a ruler so that the cutting lines are straight and even. You will need to make at least five of these clay tiles.

Then, using a pointed stick, diagonals are also drawn on the surface of the tiles along a ruler. Not deep, but so that they are clearly visible. All that remains is to use a measuring compass, opening it exactly 50 mm, to apply marks with its ends across both diagonals (Fig. 2). To dry, the tiles are placed in a secluded place, for example, on a shelf or on a dry window sill. Of course, the tiles should not be exposed to direct sunlight, and they should not be placed close to heating appliances. At room temperature, the tiles will dry in a week, after which you can begin to determine air shrinkage. To do this, take a caliper and measure, with an accuracy of 0.1 mm, the distance between the marks on the diagonals. Do not forget to inspect the samples during measurements, note changes in shape, the presence of cracks, deflections, curvatures, etc.

Let's assume that after measuring all 5 tiles we got the following results (in mm): 45.0, 45.9, 46.1, 45.6, 47.8, 46.2, 45.4, 45.5, 46, 1, 45.8. Let's calculate the arithmetic mean of this group of numbers, for which we divide the sum of the values ​​of these numbers by their number:

459.4: 10 = 45.94 mm.

Now let’s determine the percentage of shrinkage, knowing that the distance between the marks before drying was equal to 50.0 mm:

[(50.0 - 45.94)/50] x 100 = 8.12%.

This is the air shrinkage of our clay. It varies from clay to clay and ranges from 1 to 15%.

At the same time, based on the state of these same samples, we determine another property of our clay - sensitivity to drying. If after drying the samples are not deformed and there are no cracks on them, then the clay is not very sensitive to drying. The presence of slight distortions in shape or a small number of small shrinkage cracks indicates an increased sensitivity of the clay to drying. Finally, if the samples are severely deformed or cracked, the clay is highly sensitive to drying. This is a very important indicator that must be taken into account when prescribing a recipe for ceramic mass from a particular clay.

Fire properties

Sinterability is the ability of clay to produce a dense shard when fired. Researchers involved in ceramics have agreed that the ability of clay to form a shard must be determined at the same temperature, namely at 1350° C. After all, different clays are sintered at “their own” temperatures, the spread of which is very significant (from 450 to 1450° C) , and if the sinterability of each clay is determined at its temperature, then it is difficult to establish a quantitative measure of sinterability. That's why we chose one temperature.

The degree of sintering is determined by the water absorption of a shard of this or that clay fired at 1350°C: if the water absorption is less than 2%, the clay is highly sintering; from 2 to 5% - medium sintering; more than 5% - non-sintering. (Water absorption is the ability of a material to absorb water when immersed in it.) The caking ability of clays can be controlled using additives.

Since we agreed that we would be engaged in the production of majolica, that is, porous ceramics, we will not need to achieve strong sintering of the clay. However, in order to determine the sintering temperature of the clay with which to work, it is advisable to know this property of the clay.

To determine the sinterability of our clay, the same samples that were used to determine air shrinkage are suitable. And it’s not scary that they cracked during drying or changed shape. If you have access to a laboratory muffle furnace, then it is better to burn the dried samples in it.

We want to establish now how hard a shard can be baked in your oven from the existing clay without introducing any additives. Therefore, we will set the appropriate temperature in the muffle.

In the absence of a muffle, the samples are fired in a conventional heating furnace. To do this, at the end of heating the furnace, when quite a lot of ash has accumulated in the firebox, but the fuel has not yet completely burned out, dried samples are placed on top of the coals without burying them. The stove valve and ash pan are covered so that fuel combustion continues at medium intensity. When the stove is heated, it is simply closed. The samples are taken out of the furnace only after it has completely cooled, that is, after about 10...12 hours. The sintering temperature in this case will be the same as that provided by the furnace where you are going to fire your products. Typically, wood-burning stoves produce temperatures of 850...950° C. Aspen, linden and other soft woods emit less heat when burning than coniferous woods. Hard (oak, beech, elm) - more. Of course, the temperature largely depends on the draft in the furnace.

Having removed the samples from the oven, they are shaken off from ash and dust, after which they are weighed on a pharmacy scale with an accuracy of 0.1 g and placed flat in a vessel with water, immersing the samples in water not completely, but 2/3 of their thickness.

The samples are kept in water for one day, after which they are taken out, blotted with a dry cloth or blotting paper (water should not drip from them) and weighed again with the same accuracy.

Water absorption of samples is calculated using the formula:

B = [(M in - M s)/M s] x 100,

where M s is the mass of the dry sample, g; M in - mass of sample saturated with water, g; B - water absorption,%.

At least 3 samples must be subjected to such a test, then the arithmetic mean of the results obtained is calculated. This will be the water absorption value. If it turns out to be less than 2%, then the clay is easily sintered, at 2...5% it is medium sintered, and above 5% it is unsintered. If the clay is easy to sinter, no measures are required to improve its sinterability. Medium baked clay can most likely be left alone. But we’ll discuss how to increase the sinterability of non-sintered clay later.

If, after determining air shrinkage, the samples turn out to be unsuitable for determining sintering, well, say, they fell apart during drying or turned out to be severely deformed, exactly the same new samples should be prepared. But you will have to dry them more carefully and slowly, for which it is better to place them in a closed container, for example, a glass jar, and cover it with a sheet of paper. Drying under these conditions will last at least 2 weeks.

Fire shrinkage is a change in the volume of clay during firing. The degree of such shrinkage depends not only on the properties of the clay, but also on the firing temperature. As in the case of sinterability, fire shrinkage is determined at 1350° C. But in our case, fire shrinkage is important at the firing temperature, that is, at the one that the furnace will provide. Knowledge of fire shrinkage will help determine what size casting is required in order to obtain a product of the given dimensions after firing. Naturally, air shrinkage is also taken into account.

If the samples that were fired to study sintering have retained their shape well and the marks applied to them are clearly visible, fire shrinkage can be determined using them.

To do this, using a caliper or measuring compass, again measure the distances between the marks on the diagonals of the samples. Fire shrinkage is calculated using the same formula as air shrinkage. You just need to compare the distances between the marks after drying with the distances after firing. Typically, most clays have fire shrinkage of 6...8%. As already mentioned, the total shrinkage is equal to the sum of air and fire. For ordinary clays, as a rule, it is close to 15%, but significant deviations from this value are also observed.

All this information will be needed to determine the composition of the raw material mixture with which you will have to work, as well as determine the dimensions of the molds and set the modes of drying and firing of products.

So, we have figured out the properties of the plastic clay mass. Let's get acquainted with the specific properties of liquid foundry clay (slip), which will be needed when making majolica using the drain method. But first, let's prepare a sieve with a mesh size of 0.0053 mm, an Engler viscometer and a stopwatch. You are unlikely to get all this in a small town, much less in a village. But you can make both a sieve and a viscometer yourself. This will be discussed in detail in the next section, specifically dedicated to the equipment, instruments and devices necessary for working with ceramics. For now, let’s say that the design of the sieve is no different from ordinary sieves, only instead of traditional mesh, you will have to pull a nylon or nylon stocking, which will replace the mesh with a cell size of 0.0053 mm. Instead of a stopwatch, any watch with a second hand will do - an accuracy of up to 1 second is quite enough.

You will also need a porcelain mortar with a capacity of at least 0.5 liters with a porcelain pestle. An even better idea would be to purchase a laboratory porcelain mill. Keep in mind that cast iron or bronze mortars are not suitable in this case, since when grinding the components, metal in the form of fine dust will get into the slip, which can significantly affect the properties of the slip. But if there is no other choice, use a cast iron mortar.

To determine the properties of the slip, the latter must first be prepared. To do this, take 0.5 kg of dried clay and add water to it, the amount of which depends on plasticity. So, we dilute low-plasticity clays in 320 ml of water, medium-plasticity clays in 300 ml, and high-plasticity clays in 280 ml. (The moisture content of the slip in this case will be approximately 39%, 37.5% and 36%, respectively.)

So, clay and water in the required quantities are placed in a mortar, after which the clay is crushed by rubbing it with a pestle. When you can no longer feel the sand under the pestle, you can determine for the first time the fineness of grinding (grinding) of the slip. After weighing out 100 g of slip, it is poured into a sieve with a stocking mesh and the slip is washed with a stream of water to clean water. The washed residue is dried and weighed. If its mass is less than 2g (in our case less than 2%), then the slip is ready.

The mass of the residue on sieve 0053 (this is the designation for a sieve with a mesh size of 0.0053 mm) characterizes the fineness of the slip grinding. It should not exceed 2%, otherwise the slip will begin to intensively delaminate, that is, during the formation of products, larger particles will quickly begin to settle out of it, as a result, the walls of the product will acquire unequal structure and density at different heights. We also add that the grinding fineness should not be less than 1%. In the latter case, the slip thickens too quickly, so the density of the walls of the products will vary in thickness. If the grinding fineness turns out to be insufficient (the residue on the sieve exceeds 2%), the slip will have to be additionally ground so that the amount of residue fits into the desired range.

Having prepared a slip of the required quality, we begin to determine its fluidity. To do this, the slip is poured into a viscometer with a closed drain hole. After 30 seconds, the drain hole is opened and at the same time the clock starts counting down the second hand. When exactly 100 ml of slip is poured into the vessel under the viscometer, the drain hole is closed. The time during which 100 ml of slip flows out of the viscometer is its fluidity. Typically, the normal fluidity of casting slip is 20 s. If the fluidity is more than 25 s, it is necessary to introduce a thinning (plasticizing) additive into the slip. If the fluidity is less than 15 s, it is necessary to reduce the humidity of the slip, that is, add less water to the clay. In short, the fluidity of a slip suitable for casting lies within 15...25 s.

Now let's look at the thickening of the slip, which manifests itself in the fact that the fluidity of the slip decreases over time, that is, the time for 100 ml of slip to flow out of the viscometer increases after some period. Thickening is determined as follows. The slip remaining in the viscometer after determining the fluidity is kept at rest for 30 minutes, without shaking or stirring it. Then the flow time of 100 g of slip is measured again, as in the first time. This time will, of course, be longer than the first. By dividing the new slip expiration time by the previous one, its degree of thickening is obtained. If this quotient is greater than 2.2, then the slip is not suitable for formation. Its fluidity and thickening time must be regulated by additives.

Another very important property of the slip, on which both the molding properties of the slip and the quality of the future shard largely depend, is density. The slip density is determined using a hydrometer (densimeter) with a calibration interval of 1.5...1.8 g/cm³. It is not always possible to obtain such a hydrometer, but you can replace it with two or even three hydrometers, the measurement range of which covers the mentioned interval, for example, one - from 1.5 to 1.6, the other - 1.55...1.65, and third - 1.56...1.85.

In the absence of a hydrometer, density is determined by weighing a known volume of slip. For example, a measuring vessel with a capacity of at least 100 ml, pre-weighed with an accuracy of 0.1 g, is filled with slip to the mark indicating this volume. After weighing the vessel with the slip, subtract the mass of the empty vessel from the resulting mass and divide the result (difference) by the volume of the slip O w. The quotient of the division (with some reservation) can be considered the density of the slip P w:

P w = (M w - M p)/O w g/cm³.

I note that in reality the density value calculated in this way will be slightly different from the value that the hydrometer will show. The specific gravity of the slip obtained in the first case may not coincide with the density measured by the hydrometer.

Recently, it has become very fashionable to make dishes and various interior items from clay with your own hands. We at the How to Green editorial office decided to figure out the reasons for the popularity of handmade ceramics, and turned to ceramic artistElena Subbotina . She named as many as 7 reasons (in addition to the obvious - creative self-realization and acquiring new craft knowledge) why it is worth making dishes for the home and various small items for the interior with your own hands.

Reason 1: uniqueness

Obviously, you can make a 100% unique set or tea pair for your kitchen either to order or with your own hands. Doing it yourself will be much cheaper. You have the opportunity to bring to life the most daring ideas and make exactly what will fit perfectly into your interior or will be suitable as a gift for a loved one. And not only the design you need, but also the size you like. So it’s up to you to decide whether you’ll drink tea at home from huge cups and saucers, like in Tim Burton’s Alice in Wonderland, or from delicate tiny ones, like Kirsten Dunst’s heroine in the movie Marie Antoinette. By the way, making dishes for the home with your own hands is also convenient because, by creating, say, a service in the same style, you won’t have to overpay for soup or dessert plates that you don’t need, and then think about where to store them in your small kitchen. You will make for yourself only those plates, bowls, cups and mugs that you need and will use.

Reason 2: environmental friendliness

Did you know that some factories still use hazardous materials, including lead and cadmium, when making tableware? Lead glazes are very beautiful; the content of this metal gives the product a special shine. The amount of lead, of course, is small, but using this glaze is strictly prohibited. It is not recommended to even store dry food in such containers, let alone pour hot soup into a bowl of lead. In some countries there is a law that prohibits the use of lead in foodware in any quantity. However, in Russia, China, Africa, and the countries of the Southeast region, there is often no strict control over manufacturers who neglect the issue of ethics and consumer health, since purchasing bright, glossy, lead-free glazes is much more expensive in large-scale production. So think ten times before you buy a cheap, bright cup or bowl. Why do you need dishes that poison you with harmful substances? By creating your own pottery, you can control which materials and glazes you use to create your plates and cups. By the way, ceramics can be bright and without colored glazes at all. There are natural colored clays: blue, green, black, and even ordinary light types have a beautiful natural color. In order for the products to be functional and not allow water to pass through, they must be covered with colorless or white glaze, but you can completely refuse colored glaze or choose safe, proven options.

Reason 3: replenishment

If suddenly careless guests or you yourself dropped your favorite mug and broke it, it’s okay. Your service will not suffer from this, because you can always make a couple more plates or cups. The same is true in the case of a new addition to your family - the birth of a baby or the marriage of a beloved brother. You can always make the missing set of dishes in a couple of hours. If you went on a trip, you probably noticed very interesting interior items - large vases, picture frames, candlesticks. Sometimes things are so beautiful, you just fall in love with them, but taking them with you from a trip is difficult and too troublesome. And why? It’s enough to take a couple of photos on your smartphone and, when you return from vacation, make copies of your favorite interior items or dishes, but in your own style and to suit your tastes and needs.

Photo: ceramics studio Ceramic Forest

Reason 4: quality

A fairly common story: you bought beautiful dishes from an online store, but they turned out to be of poor quality. The bright pattern on the mug began to peel off after washing, and knife marks appeared on the plates. When producing your own dishes, especially in a ceramic workshop under the supervision of a master, such excesses are excluded. First of all, you will be taught how to handle clay correctly and will be explained the sequence of the technological process that will make your dishes high-quality and practical. So you can put it in the microwave and wash it in the dishwasher without any problems. There is no risk of cracks or peeling paint.

Reason 5: saving the family budget

If you haven’t decided to produce a whole set, but just for fun, you’ve attended an introductory course on ceramics and made a couple of mugs, then even this knowledge will be enough for you to begin to understand tableware, types of clay and glazes, and the artist’s skill. If suddenly in a store a saleswoman begins to assure you that a pair of coffee costs 20,000 rubles because it is rare blue clay, then you can safely clarify whether it is natural or just an artificial color (a pigment mixed into ordinary white clay)? Dyed clay carries no value and you are paying solely for the brand. Expensive ceramics stores also like to use stamping. This means that the shape of the products is not unique: the patterns that are applied to them can simply be printed, and not drawn by the master. It’s another matter if you see on a market somewhere in the mountains of Andalusia a designer jug ​​made of expensive materials, unique in shape and painted. You will immediately understand how much work the master has put into it and why it costs a decent amount. By the way, if the author of this work of art is suddenly exhibited in some gallery or museum of modern art, then the purchased jug can also be sold at a profit to collectors.

Reason 6: the issue with gifts has been resolved

Unique DIY ceramics are also exclusive gifts for family, friends and colleagues. You can personalize the dishes, leave initials on them, create any images and write wishes. For example, if you have unique lace left from your grandmother, then you can make an entire service with a unique print based on it. Thus, each family member will have a memory printed on a mug, plate, dish or teapot. Clay is an amazing living material that allows you to bring any idea to life. We use ceramic products every day, so these gifts are not only beautiful and unique, but also very useful for any person, regardless of their gender and age. By the way, it is not at all necessary to give dishes as a gift. You can create almost anything from ceramics. For example, floor tiles are an excellent gift for renovating the bathroom in your beloved mother’s apartment. Other interesting options:

• ceramic handles that will transform an ordinary stamped wooden chest of drawers into a real work of art for the chest of drawers;
• decorative sculpture, for example, for the garden;
• pots for indoor or garden flowers;
• tray;
• whistles for children;
• brooches for friends;
• soap dish and other bathroom accessories.

Photo: ceramics studio Ceramic Forest

Reason 7: additional income

After you learn how to make dishes with your own hands, make all the necessary plates for your own home, and give gifts to your friends and colleagues, it is quite possible to monetize your favorite hobby. Create, say, an online store on Instagram and produce unique dishes in your own style to order. By the way, the most popular are craftswomen with a fairly narrow specialization, who make, for example, beautiful openwork cake stands, unusually shaped mugs, or fruit dishes with unique designs. Who knows, maybe one day you will make plates not only for your beloved man or relatives as a gift, but also for an entire restaurant.

Where to make your own dishes?

You can make your own cookware at home. To do this, you will need the necessary materials - clay, stacks, glaze, and so on. You can fire finished products at home; for this, there are furnaces that are suitable for a voltage of 220 W. But they are quite expensive - from 100,000 rubles. Therefore, at the initial stage it is easier to carry out firing in special kilns in ceramic workshops. They usually accept items not made by them for firing without any problems and for a very reasonable fee. Before purchasing materials for your home, we would recommend that you take an introductory course on working with clay from a specialist. Typically, ceramic workshops offer different options. Depending on the amount of information, such training will take you from 2 hours to several days and will cost from 2-3 thousand rubles, taking into account the cost of all materials. If you haven’t yet decided what exactly you want to make from ceramics, it makes sense to purchase a subscription to the workshop and attend master classes that interest you. It will be easier and cheaper than immediately taking long, expensive courses. Typically, such master classes are held for several people at once, so you have an original option for spending leisure time with a friend or loved one.

By the way, you can make all the dishes that you see in the photo in this article with your own hands already in the first lesson...

DIY pottery

Have you ever watched how a swallow makes its nest? In addition to blades of grass, used by all feathered builders, clay is also used. Moreover, clay is the main building material for swallows. No wonder people say: “A bee sculpts from wax, and a swallow from clay.” Softening the clay with a liquid secreted by special glands, the swallow, like a real potter, sculpts a deep bowl, lump by lump. When it dries, it becomes so strong that if it accidentally falls, it will not break. It is quite possible that in very distant times, observations of swallow work gave people the idea of ​​​​building adobe dwellings and mud huts. Until now, using the “swallow technology”, raw bricks are made from unfired clay, used for the construction of various buildings, not only rural, but also urban. As you know, highly compacted clay does not allow moisture to pass through, so in folk construction not only walls, but also floors and roofs were made from it. To increase the strength of the adobe floor, it was watered with salt water from time to time.

Clay has become so firmly established in the construction industry that even in our reinforced concrete age, a third of the planet’s population lives in adobe dwellings. And this is not counting the houses made of baked bricks.

In ancient times they wrote on thin clay tablets in the same way as they write on paper now. (By the way, white clay is necessarily included in modern paper. This means that to some extent we still write on clay.) Among the clay tablets found during excavations there are all kinds of documents: laws, certificates, business reports. Clay tablets became the pages of the very first books written by ancient authors. Epic poems, religious hymns, proverbs and sayings composed in those distant years were immortalized on them. After completing the inscriptions, some tablets were only dried well in the sun, while others, more valuable, intended for long-term storage, were fired. Since time immemorial, people have sculpted from clay objects necessary for everyday life, primarily dishes. The only problem is: dishes made from unfired clay are very fragile and are also afraid of moisture. Only dry foods could be stored in such containers. While raking up the ashes of a dying fire, the ancient man more than once noticed that the clay soil in the place where the fire burned became hard as stone and was not washed away by rain. Perhaps this observation inspired a person to burn dishes at a fire. Be that as it may, clay baked in a fire was the first artificial material in the history of mankind, which later received the name ceramics. With the development of technology, molded and dried clay products began to be fired not in fires, but in special furnaces - forges. In Rus', the very word “potter” comes from the name of kilns. In the old days, craftsmen who worked with clay were called potters, but over time the letter “r”, which made it difficult to pronounce, was lost. Ceramics are the most common finds of archaeologists. Indeed, unlike wood, clay does not rot or burn, does not oxidize, like metal. Many clay objects have reached us in their original form. This is primarily a variety of dishes, lamps, children's toys, religious figurines, casting molds, sinkers for fishing nets, spindle whorls, spools of thread, beads, buttons and much more.

In the hands of talented craftsmen, ordinary things turned into true works of decorative and applied art. The art of ceramics reached high development in Ancient Egypt, Assyria, Babylon, Greece and China. Many museums around the world are decorated with dishes made by ancient potters. The old masters knew how to sculpt dishes that were sometimes gigantic in size. The Greek pithoi - vessels for water and wine, reaching a height of two meters - amaze with their high technical skill. It was in a pithos vessel, and not in a barrel, as is commonly believed, that the ancient Greek philosopher Diogenes lived.

In our time, many of the secrets that the ancient masters possessed have been lost. Despite the high development of production, modern ceramists have not yet been able to uncover the secret of preparing the glaze that covers two large vases discovered during excavations by Chinese archaeologists. When water was poured into the found vases, the glaze immediately darkened and changed color. As soon as the water was poured out, the vessels regained their original whiteness. Ho

Even though these amazing chameleon vases were made by Chinese potters more than a thousand years ago, they have not lost their amazing properties. Ancient Rus' was also famous for ceramics. Bowls, dishes, jugs, egg capsules, wash basins, stove pots and even calendar jugs came out of the potters' workshops. Each calendar was a jug on which certain signs were applied with stamps in a rectangle allocated to each month. In addition to calendars designed for the whole year, there were agricultural calendars covering the period from April to August, that is, from sowing to grain harvest. On such a calendar, special signs indicated the most important pagan holidays, dates for field work, and even days when it was necessary to ask the sky for rain or buckets (sunny weather). Blessed water was poured into the calendar jug ​​itself, which was used to sprinkle the fields during the prayer service. Russian potters painted tableware with special ceramic paints or engobes (liquid colored clays) and covered them with glassy glaze. Especially a lot of black-polished clothes were made. Slightly dried items were rubbed to a shine with a polish (smooth stone or polished bone), and then fired over a smoky flame without allowing oxygen into the forge. After firing, the dishes acquired a beautiful silver-black or gray surface, at the same time it became more durable and less permeable to moisture. There is pottery in every modern home, although it is difficult to believe that sparkling white porcelain cups and plates are relatives of smoky stove pots, throaters and all kinds of makhotkas fashioned from dark clay. But dishes made of white and dark clay are not rivals; each is good for its purpose.

The most aromatic tea can only be brewed in a porcelain teapot, and the most delicious cow's milk varenets can only be prepared in a clay pot and even in a Russian oven.

In modern urban housing, clay is also present in the form of all kinds of facing slabs, bathtubs, and sinks.

In a word, clay is always a modern material, without which it is impossible to do without either in the present or in the future. Since ancient times, clay has served man not only as a raw material for ceramics and construction. Traditional healers used clay as a kind of healing agent. For example, strained veins were treated with a plaster made from yellow clay diluted in vinegar. In order to relieve pain in the lower back and joints, a clay patch diluted in hot water with the addition of kerosene was applied to the sore spots. Healers preferred stove clay, using it for divination, whispering against the evil eye and treating fever. Various pottery dishes were used as medical equipment. Medicines were prepared in some vessels, and dried herbs and roots were stored in others. And the smallest pots, which were called makhotkas due to their small size, were used for colds as ordinary medical jars. Probably the first medical heating pad was also made of clay. At first, a jug with a narrow neck was used as a heating pad, into which hot water was poured. Then, on orders from doctors, potters began to make special medical heating pads in the form of a low vessel with a flat, wide bottom and a tightly closing neck. Even an ordinary red brick is said to have been put in the service of health. It was heated in an oven, then onion peels were sprinkled on top, inhaling the smoke that appeared. Modern medicine confirms that such inhalation helps with colds. Using a hot brick, you can also disinfect a room and drive mosquitoes and flies out of it. Only in these cases, instead of onion peels, wormwood and juniper branches were used.

Few people know that the inhabitants of the North - the Chukchi and Koryaks - used clay... for food. Of course, not just any clay, but white clay, called “earth fat” by the northerners. They ate earthen fat along with reindeer milk or added it to meat broth. Europeans did not disdain “edible” clay, making delicacies from it like candies.

I was on the topanka..."

I was at the Kopanets, I was at the Topanska, I was at the circle, I was at the fire, I was at the scald. When he was young, he fed people, but when he got old, he began to take swaddling clothes.” In the old days, anyone could guess this riddle. The hero of the riddle is an ordinary stove pot. Using his example, you can trace the entire path that clay takes before becoming a ceramic product. “Kopants” was the name given to the village potters to the pit or quarry where clay was mined. From the kopanets, the clay fell onto the “topanets” - a flat place in the yard or hut, where they trampled it with their feet, carefully kneading it and picking out the pebbles that got into it. After such processing, the clay went to the “circle”, that is, to the potter’s wheel, where it took the shape of a pot or some other vessel. When the pot was completely dry, it was sent to the “fire,” or rather to the oven, where after firing it became hard as stone. But in order for the pot not to absorb moisture, it had to be “scalded.” To do this, it was dipped hot into kvass grounds or liquid flour mash.

The second part of the riddle figuratively and briefly shows the further fate of the finished pottery. It is hardly worth specially explaining how the stove pot “fed people,” but why it began to “become swaddled” in old age is hardly clear to modern people. The fact is that in the past, housewives were in no hurry to throw away old cracked pots. They were wrapped in narrow steamed ribbons of birch bark, as if they were swaddling. Pots and other pottery wrapped in birch bark could serve for many years. We will have to remember this old Russian riddle more than once, but for now we will talk about the Kopan people and “living clay”.

Potters called “living clay” clay that is found in nature in its natural state.

Clay found in nature is so diverse in composition that in the depths of the earth you can actually find a ready-made clay mixture suitable for making any type of ceramics - from sparkling white earthenware to red stove bricks. Of course, large deposits of valuable types of clay are rare, so factories and plants for the production of ceramics arise near such natural storehouses, as, for example, in Gzhel near Moscow, where white clay was once discovered. Every self-respecting village potter also had his own, albeit small, treasured deposits, or more simply, Kopan pits, where he extracted clay suitable for work. Sometimes they had to travel many miles to get the clay they needed, extracting it from deep holes with incredible difficulty. Moreover, one deposit was not always enough, since different products required different clay compositions. For example, rich ferruginous clay is best suited for black-polished ceramics. It is highly plastic, perfectly shaped on a pottery wheel, and after drying it can be ironed to a mirror shine. Dishes made from such clay do not allow moisture to pass through and are highly durable. One problem: oily clay cracks easily when dried and subsequently fired. Products of thin clay containing a significant amount of sand have a rough surface, and they also strongly absorb moisture. But when drying and firing, skinny clay very rarely cracks. For good clay, the golden mean is preferable when it has medium fat content.

Clay containing less than 5% sand is considered oily, while lean clay contains up to 30% sand. Medium fat clay contains 15% sand.

You can find suitable clay for modeling and pottery almost anywhere, if you wish. In addition, a small amount of clay can always be “corrected” by elutriation and other methods. Clay may lie immediately below the soil layer at a shallow depth. In garden plots it can be found during various land works. Layers of clay quite often come to the surface along the banks of rivers and lakes, in slopes and slopes of ravines. In the Non-Black Earth Region there are areas where clay is literally underfoot and in wet weather on country roads it turns into a solid mess, causing indignation among passers-by. Even from such “dirt” collected on the road, small decorative items can be sculpted and then fired. But, of course, this should not be done. Even where there is clay soil all around, you need to dig at least a shallow ditch to get to cleaner and more uniform layers.

Clay suitable for modeling can be successfully prepared even in a big city. After all, somewhere nearby, builders are digging foundation pits for a new house, or water or gas pipelines are being repaired. In this case, clay layers that lay at great depths appear on the surface.

You can determine the suitability of clay for modeling in a fairly simple way. From a small lump of moistened clay taken for testing, roll a rope between your palms about the thickness of your index finger. Then slowly fold it in half. If at the same time no cracks or very few of them form at the bend, then the clay is quite suitable for work and, in all likelihood, it contains 10-15% sand.

Each type of clay changes its color at a certain stage of modeling, drying and firing. Dried clay differs from raw clay only in a lighter tone, but when fired, most clays dramatically change their color. The only exception is white clay, which, when moistened, acquires only a slight gray tint, and after firing remains the same white. The color of “living clay,” which is usually in a wet state, is most often deceptive. After firing, it can suddenly change dramatically: green will turn pink, brown - red, and blue and black - white. As you know, craftswomen from the village of Filimonovo, Tula region, sculpt their toys from black and blue clay. Only after being dried in a kiln do the toys become white with a slightly creamy tint. The miraculous transformation that occurred with the clay can be explained very simply: under the influence of high temperature, organic particles burned out, which gave the clay a black color before firing. By the way, such particles are found in chernozem, where they also determine the color of this soil. The color of clay, both in the raw and in the fired state, is also influenced by various mineral impurities and metal salts contained in it. If, for example, the clay contains iron oxides, then after firing it turns red, orange or purple. Based on the color that the clay acquires after firing, there are white-burning clay (white color), light-burning clay (light gray, light yellow, light pink color), dark-burning clay (red, red-brown, brown, brown-violet color). To determine what kind of clay you are dealing with, make a plate from a small piece or roll it into a ball, which, after thoroughly drying, is fired in the oven. Place the prepared clay in wooden boxes and fill it with water so that individual lumps protrude slightly above the surface. It is advisable to immediately prepare as much clay as possible. When there is an abundance of clay, only a small part of it is consumed, and the rest will be constantly aged. The more the clay is kept wet, the better. Previously, potters kept clay in the open air in the so-called clay pit - a special pit, the walls of which were made of logs, blocks or thick boards. The clay had to lie in the clay pot for at least three months, but sometimes it was in open storage for several years. In spring and summer it was burned by the sun's rays, in the fall the winds blew and rained, in winter it froze in the cold and thawed during the thaw, then melt water penetrated into it. But all this was only beneficial for the clay, since it was loosened by numerous microcracks, while harmful organic impurities were oxidized and soluble salts were washed out.

The centuries-old practice of folk craftsmen has shown that the longer the clay is aged, the better its quality...
The clay, which has the optimal fat content and has aged well, just needs to be thoroughly kneaded and the pebbles that accidentally fall into it should be selected. In the past, clay was kneaded in a pottery or hut on the floor sprinkled with sand, which is called “topanets” in the riddle about the pot. Often the whole family, including children, was involved in kneading and cleaning the clay. The clay was trampled with bare feet until it turned into a thin plate, which was immediately rolled into a roll. The roll was then folded in half and trampled again. When the clay regained the shape of a plate, a new roll was rolled up. This was repeated up to five times until the clay turned into a homogeneous mass, soft and pliable, like pie dough. By the way, well-washed and cleaned clay, ready for pottery work, is called clay dough.

Sifting clay

If you decide to sift the clay, then spread it in small lumps on a wooden floor and dry it in the sun (Fig. 1.1). In winter, the clay dries well in the cold, spread out under a canopy where snow does not fall. A small amount of clay can be dried indoors, on a warm stove or on a central heating radiator. Of course, the smaller the lumps, the faster the clay will dry. Pour the dried clay into a thick-walled wooden box and break it with a tamper - a massive piece of tree trunk with handles fixed on top (1.2). Sift the resulting clay dust through a fine sieve and remove from it all kinds of impurities in the form of pebbles, chips, blades of grass and large grains of sand (1.3). Before modeling, the clay powder is kneaded in the same way as bread dough, adding water from time to time and thoroughly mixing the clay mass with your hands. It is advisable to store some of the clay powder in case the clay dough needs to be quickly made thicker, but there is no time for drying and evaporation. Add the required amount of powder to the liquid clay dough and then knead well.

Clay elutriation

When elutriated, the clay not only becomes purified, but also becomes fattier and more flexible. Therefore, clay that contains a lot of sand and has low plasticity is most often elutriated.

You need to soak the clay in a tall vessel, such as a bucket.

Pour one part clay with three parts water and leave overnight. In the morning, thoroughly stir the clay with a stirrer until a homogeneous solution is obtained. Then let the solution sit for a long time. As soon as the water clears from the top, carefully drain it using a rubber hose. But it is not so easy to drain the water without muddying it. Therefore, even in ancient times, a simple and ingenious device was invented, which is still used by Japanese potters (Fig. 1.4). Several holes are drilled vertically in a wooden tub at a short distance from each other. Before filling the tub with liquid clay mortar, each hole is plugged with a wooden stopper. Heavier grains of sand and various kinds of pebbles settle to the bottom first. Then, after settling, clay particles fall down. Gradually, the water from above brightens and finally becomes transparent (1.4a). As soon as the level of clear water seems just below the top hole, the plug is pulled out and the cleared, settled water is poured out of the barrel (1.46). After some time, remove the plug located below. This way all the settled water is gradually drained out. To speed up the process of clay settling, bitter Epsom salt is first added to the solution (about one pinch per bucket). Instead of a wooden tub, you can use a suitable metal container. At different levels, short tubes are soldered into it and plugged with plugs.

After removing the settled water, carefully scoop out the liquid clay, leaving the bottom layer untouched, which contains pebbles and sand that have settled to the bottom. Pour the clay solution into a wide wooden box or basin and place it in the sun so that excess moisture evaporates from the clay faster (1.5). As soon as the dried clay loses its fluidity, stir it with a shovel from time to time. After the clay acquires the consistency of thick dough and stops sticking to your hands, it is covered with plastic film or oilcloth and stored until the start of modeling work.

Leaning Supplements

When making large products, so-called leaning additives are introduced into fatty clay, which help reduce shrinkage during drying and firing, thereby preventing the appearance of cracks and warping on the product.

Even in ancient times, when making large vessels intended for storing food, grus - coarse sand obtained by crushing sandstone - was added to the clay dough. But the most common waste material has always been fine sand. To remove foreign matter from the sand, it is washed several times with clean water and then dried. Sometimes other thinning materials are added to clay to give it additional properties. Ceramics will become lighter and more porous if you add a little sawdust to the clay dough. Instead of sawdust, folk craftsmen of Central Asia add poplar fluff and swamp plant cattail fluff to the clay, as well as crushed animal hair. The admixture of so-called fireclay makes the ceramics more fire-resistant. Fireclay can be made from refractory bricks, which are first pounded and sifted through a sieve, removing ceramic dust. The crumbs remaining in the sieve, no larger than a millet seed, are fireclay. It is added to the clay dough no more than 1/5 of the total mass.

Along with fireclay, crushed and sifted ceramic ware is used to produce fire-resistant ceramics.

“Breaking” the clay

Immediately before modeling, in order to remove air bubbles from the aged clay and increase its uniformity, the clay dough is “beaten” and kneaded. “Killing” the clay is indispensable in cases where the clay, for some reason, has not been cleaned well enough and there are small pebbles and other foreign inclusions in it. Processing begins by rolling a piece of clay into a bun (Fig. 2.1), which is then lifted and thrown forcefully onto a table or workbench. In this case, the bun is slightly flattened and takes the shape of a loaf. Take a pottery string in your hands (steel wire with two wooden handles at the ends (2.2)) and cut the “loaf” into two parts (2.3). Having lifted the top half, turn it over with the cut side up and throw it forcefully onto the table. The lower half is also thrown onto it with force, without turning it over (2.4). The stuck halves are cut from top to bottom with a string, then one of the cut pieces of clay is thrown onto the table, and the second one is thrown onto it (2.5). This operation is repeated several times. When cutting clay dough, the string pushes out all kinds of pebbles encountered along the way, opens voids and destroys air bubbles. The more cuts you make, the cleaner and more uniform the clay dough will become.

You can also process clay dough using a carpenter's plow or a large knife (Fig. 3). The lump of clay is thoroughly compacted using a massive wooden mallet (3.1). Then it is pressed forcefully against a table or workbench and the thinnest plates (3.26) are cut off with a plow (3.2a) or a knife. All kinds of foreign inclusions that fall under the blade are thrown aside. The thinner the slices are cut, the cleaner and more uniform the clay dough becomes. The plates obtained after planing are again collected into a single lump and compacted with a mallet until it becomes monolithic (3.3). The lump of clay prepared in this way is planed again. These techniques are repeated until the clay dough becomes homogeneous and plastic.

Shift clay

This is the last stage of preparing clay dough intended for modeling. Take a lump of clay in your hands (Fig. 4.1) and roll it out so that you get an elongated roller (4.2). Then the roller is bent in half (4.3) and crushed so that it again forms a rounded lump (4.4). From this moment on, all miner operations are repeated in the same sequence several times.

The plasticity of clay dough depends not only on the uniformity of its structure and composition, but also on humidity.

If the clay is too dry, it is generously sprinkled with water before each subsequent shift.

Determine the plasticity of clay in a way already known to you. A small lump of clay (4.5a) is rolled out between the palms (4.56). The resulting tourniquet is bent in half. If the clay has high plasticity, then not a single crack will appear at the bend of the rope (4.5c).

The presence of cracks indicates that the clay is too dry and needs to be moistened (4.5g).

There are many folk ways of preparing clay dough. In some regions of Russia, toy makers knead and then separate the clay into separate pieces in the following way. The clay lump (Fig. 5.1) is flattened with a wooden hammer (5.2). The resulting plate is rolled into a roll (5.3). The roll is crushed with a hammer and molded into the same lump that was at the very beginning (5.4). The molded lump is flattened again (5.5) and the plate is rolled into a roll (5.6). Having done all this several times, the roll is thoroughly kneaded and a tourniquet is rolled out of the resulting lump, which is cut into “slices” with a knife (5.7). Each “piece,” depending on the size of the future workpiece, is cut in turn into two or four parts (5.8). Each half and quarter is rolled out in the palms, obtaining blanks in the form of balls of the same size (5.9). The blanks are placed in a wooden box, covered first with a moistened cloth, and then with oilcloth or plastic film. Sometimes they are placed in some kind of metal container with a lid on top. In this form, the blanks can be stored for more than a month without losing their original plasticity.

Drying clay products

Before getting into the “fire,” each clay product must go through a preparatory stage called drying.

Drying is a rather lengthy process. Haste can negate all previous work: when drying quickly, the product becomes covered with numerous cracks and warps. At the first stage of drying, moisture from the product should evaporate as slowly as possible. In the first days, folk craftsmen dry dishes and toys indoors or under a canopy in a quiet, windy place where there are no drafts. Pre-drying takes two to three days. After this, the products were dried in a heated oven. The better the clay dries, the greater the hope that there will be no defects during firing.

A product that has a complex shape with many details must be dried with extreme care, for example, by placing it in a metal container or box, covering it with a sheet of newspaper on top. A large product can be covered on top with a dry cloth. On the second day, remove the rag, but continue to dry the product in the shade. On about the fourth day, a medium-sized product can be dried on a stove or on a central heating radiator. Dried clay acquires sufficiently high strength necessary for further processing. Before firing, each product must be carefully inspected. If cracks are found, they must be carefully repaired. The crack is moistened with water and covered with soft clay. In addition to cracks, the product may contain all sorts of irregularities, accidental deposits, clay chips adhering to the surface and small scratches. Damaged areas should be treated with a scraper and cleaned with fine-grained sandpaper, and then remove clay dust with a wide brush or broom.

To give the product shine, polishing is used. One of the ancient methods of polishing is very simple. The surface of the dried product is rubbed with any smooth object, compacting the top layer of clay until shiny.

After firing, the shine becomes stronger. Polished dishes can be safely used in the household, as they are quite moisture resistant. In Rus', polished dishes were additionally subjected to blackening for decorative purposes. To do this, at the end of firing, some kind of smoking fuel, for example, var, was thrown into the furnace. Absorbing smoke, the vessels turned black, retaining their shine. There is another way to blacken dishes. Heated ceramics are thrown into sawdust or chopped straw.

Firing clay. Construction of a traditional pottery forge

Old Russian potters cut their forge into the side of a hill. You can see how it looked in the picture, in which the forge is drawn in section.

Furnace for firing ceramics

Old Russian pottery forges: a single-tiered one from Belgorod (general view) and a two-tiered one from the Donetsk settlement (section).

Handicraft forges of open and closed types.
You will need a lot of clay for the forge. First it must be carefully prepared. The clay should not be too greasy - to one part of clay you need to add three parts of sand. After adding water, knead the mass in a large trough. Make sure it is not too liquid! To mix, whittle a large wooden shovel out of a board.

Having chosen a place for the oven, place a layer of clay on it and compact it well. On this layer, make a platform of bricks or boulder stones (use only granite stones, limestone is not suitable for this). Fasten the stones with clay mortar.

On this site we will lay out a round oven with a diameter of approximately 1 m. It is made like a very large pot from strands. The strands need to be thick, with a diameter of at least 20 cm. The thicker the walls of the oven, the better it will hold heat.
Having laid out the first circle, continue laying out the strands in a spiral. Having laid every three rows, level the walls and tamp them down with a wooden mallet.

Having raised the walls to a height of 30 cm, the lower chamber of the forge is ready, firewood will burn in it.
Now you need to install the grates on which you will place the fired products. For the grate bars, you need to find iron rods, gratings, and meshes in advance.

Lay the rods across the stove at a short distance from each other so that the clay products do not fall between them. If the rods protrude slightly beyond the edges of the forge, this is not a problem.

Now continue to build walls, reducing the diameter of the spiral with each turn. Now the second chamber is ready, in which the fired products will be placed. We leave a round hole at the top - a hatch for loading the forge.
Cut the hole for the firebox through which the firewood is placed with a large knife or sapper shovel immediately after the walls are erected, before the clay has dried.

Near the “entrance” to the stove, make a clay gate from strands. You can decorate the stove with pasted patterns - let it be, for example, a fire-breathing dragon.
Depending on the weather, the finished forge takes 10-15 days to dry. It is better to cover it with burlap for one or two days and then dry it in the open air. If cracks form during drying, fill them with clay mass. Cover the forge from rain with a piece of polyethylene, or even better, build a small canopy over it.

When the forge dries, it needs to be fired. It’s good if by this time you also have accumulated products for firing - then you will save both firewood and time. The forge is loaded through the top hole. First, large products are placed on the grates, then smaller products are placed between them and on them. The hatch is covered with a sheet of iron and covered with shards and dry earth. But leave a small gap on top for the smoke to escape, otherwise there will be no air movement and the fire will not flare up.
First, the stove is heated over low heat, and then more and more wood is added.

Firing begins in the morning and ends in the evening. At night the forge will cool down, and in the morning it will be possible to “unload” it, that is, remove the finished products from it. If you don't have enough clay on hand to make a forge, you can build one using bricks using the same pattern. The temperature in the pottery forge reaches 900°C. Products in the furnace are heated evenly.

Clay scald

Scalding is the last stage of processing pottery in village potteries.

After scalding, pottery becomes less permeable to water and also more durable.

Scalding is done immediately after the still hot dishes are removed from the furnace. Holding it with tongs, it was dipped into a pre-prepared liquid paste solution made from rye or oatmeal. The pottery was also boiled in kvass grounds, which usually remained at the bottom of the kvass container. Potters of Central Asia used whey for the same purposes.

Flour broth and kvass grounds penetrate deep into the walls of the pottery, scald and reliably clog its pores. After scalding, the appearance of the dishes also changes: it is covered with numerous dark spots, giving it a unique identity. In addition, spots, according to village potters, protect the contents of the vessel from the evil eye.

Gradually, scalding began to be used less and less, potters increasingly use glaze or glaze - covering products with the thinnest layer of glass.