Clay firing technology at home. Send your questions on the topic of modeling - I will be happy to answer

So reproduction actually follows from the presence of dishes after the BP. Cups, bowls, jugs for drinks, all this will be missed in any case, no matter how We prepare. We often come across clay, and it’s not so difficult to sculpt from it, but it’s quite difficult to burn it.

Option one

Before firing, clay products must be dried at room temperature for 3-5 days, depending on the size. This evaporates most of the moisture in the clay. If the product is dry on the outside, and moisture remains inside, it may explode during firing. It also explodes when stones are present in the modeling clay. After firing, clay acquires new qualities - strength, rigidity, durability.

At home, when there is no muffle furnace, products can be fired on a conventional electric or gas stove.

In this lesson, we will use an electric stove.

Using for firing their clay products - a small frying pan and a cast-iron pot. At the bottom of the pan, pour fine sand for gradual heating. We put the figurine on the sand and cover it with a pot.

The heating temperature must be increased gradually. First, I turn on the minimum heating for 30 minutes, then we increase the temperature to a maximum for 5-6 hours. Before removing the clay figurine, you must wait for it to cool completely.

Second option

I happened to use the most primitive and unpredictable method in the country - firing at the stake (this is not recommended in the specialized literature, since this wild method can ruin your work). I decided to conduct an experiment. I folded a small double-sided masonry of bricks (it is better if it is possible to lay it out on four sides and leave room for a closed hole to make it easier to kindle a fire). The height of my masonry was 4 bricks, but this is not so important, the main thing is that later it would be possible to cover this masonry from above along with the product and leave it until the fire completely fades and cools down. And you need to put the product so that the coals do not come into contact with it. To protect products from contamination and mechanical damage during firing in an open fire (on a fire and in a furnace), they can be placed in special capsules. The simplest capsules are made from cans, punching several small holes in them so that the products do not darken during firing.

First, kindle a fire (only birch logs are suitable), then make a central place for the dried (this is a prerequisite for any firing!) Product, and place it on a brick base or in a capsule on the ground so that there is a high temperature on all sides when the fire flare up (this is necessary for uniform firing). A more or less gradual increase in temperature will be required. I heated the product in an electric oven and, in a warm mitten, transferred it to a heated place by the fire (to avoid temperature differences). If you put it cold, then do not let the fire close at the beginning of firing, let it warm up, then observe the temperature. When we cook kebabs, we protect the meat from fire, and clay can not be protected, just let it gradually get close to it so that the product does not break from a sharp increase in temperature, and when the fire stops rising, you can cover it with something fireproof from above (with a lid from a brazier, a piece of an old metal sheet, etc.). I had a rusty roofing piece at hand, with which we blow the fire to kindle. Then you can leave it uncontrollably to burn out and cool. The whole burning process is at least three hours, and it will take a slow time to cool down, so in the evening, and running, nothing will work (you need to watch the firing). The product must be heated from all sides, otherwise you will hear clicks from breaks (it is better not to plant children nearby, suddenly a fragment will fly off), such a practice is possible with this method. Successful results are obtained with small products, whistles, but you still do not have a guarantee to save each of them.

Many of us like to sculpt something out of clay. Making crafts is an exciting and creative process. But if you leave them in the form in which they are, they will quickly collapse. To give clay products new characteristics, they are affected by high temperatures. This is called roasting. Due to it, the clay loses moisture, the weight of the craft decreases. Clay becomes a single strong object, liquid resistance appears. The fired product is made more durable and ready for use. If desired, it can be painted.

Preparation of clay products for firing

Before firing, the product must be dried well. The drying time depends on the size of the craft: it can last from two days to a week. Drying is carried out at room temperature in a dark place without excessive moisture. It should not be such that the sun's rays fall on one side of the craft, while the other remains in the shade. If the product is not dried properly, it may crack and small parts may fall off. Therefore, you should not dry near heating appliances. When drying is insufficient, defects appear during firing. The craft may explode when heated if moisture remains in it. This can also happen when there are stones or air bubbles in it. The explosion occurs because different structures react differently to the influence of high temperature.

It is advisable to check the dried product for cracks. If they are found, they are removed with liquid clay. But it is not a fact that this will save the craft from destruction when heated. It is also useful to sand the craft with sandpaper to remove small bumps and other defects that have arisen during modeling. After all these procedures, the craft is ready for firing.

Conditions under which clay is fired

There are certain requirements for the temperature and duration of firing. Let's consider them in more detail:

The firing temperature of clay products should increase smoothly. Also, the product should gradually cool down. With sudden changes, the craft can simply explode. The first 120 minutes the thermometer value should not exceed 390 degrees Celsius. The range itself is between 200-1000 degrees.

The process can last from 8 hours to several days. It depends on the size of the fired object. The larger it is, the more time it will take.

The firing temperature of clay also depends on the presence of sand in it. The smaller it is, the smaller it is set.

Firing clay products at home

Burning clay is, of course, more difficult than sculpting from it. If possible, clay products can be fired in a muffle furnace. It allows you to change the value of the thermometer at your discretion. After the procedure, the oven is turned off and the product is allowed to cool. But what if there is no access to such a furnace? There are the following ways of firing clay with your own hands:

• Roasting in the oven. For him, a cast iron pan and clean sand are taken. The frying pan is placed inside. The product is placed in it and closed with something fire-resistant. The process cannot be left unattended. It is necessary to ventilate the kitchen frequently. They bake in the oven for one hour at a thermometer value of about 200 degrees. But it should be borne in mind that this firing method is available only for small objects. For example, for beads, small cups, souvenirs, etc.
• Firing in a Russian kiln. Quite a difficult task, because difficult to control the temperature value. To avoid the influence of strong temperature changes, the product must be placed in a cup with sand. The craft remains inside until the oven burns out completely and then cools down.
• Roasting on an electric stove. For the procedure, a small frying pan is taken. Sand is poured into it and the product is placed. From above it is all closed with earthenware. The heating temperature does not rise immediately. For half an hour, the smallest heating is turned on. Then the temperature rises to a maximum for 5-6 hours.
• A fire can also be used for roasting. This method is suitable for small crafts. For the procedure, a tin can is taken, a toy is placed in it. So that the products do not darken in the process, small holes are drilled in the jar. Next, the container is placed on fire. This frees up space in the center. So that the toy does not become covered with cracks from strong heat, it is better to warm it up a little before that. Of course, the result will not be the same as in the oven, but what is already better than nothing. In order for the flame temperature to be stable, it is better to breed it inside the brickwork. Then, from above, the construction of bricks is closed with something to allow the fire to burn out and cool down.

If you decide to do your own pottery making, we invite you to familiarize yourself with our line of pottery equipment.

What else is important to know

If there is not much time, firing can be carried out in several stages, raising the maximum temperature over and over again. After the basic firing, the craft can be treated with a special mixture and fired again. In this way, crafts are covered with glaze. It should be borne in mind that in the process of moisture loss, the product may become smaller than expected. Therefore, you need to sculpt in advance so that the size is a little larger. Don't forget about safety too. During the firing process, chemical compounds evaporate. Therefore, when firing clay products at home, the room must be constantly ventilated. Remember that you are dealing with high temperatures, due to which, if you are not careful, you can get burned. It is also worth remembering the possibility of an explosion of crafts.

Proper firing of clay at home can only be achieved with experience. Don't be discouraged if you don't get the desired result the first time. Constant training will lead to success, and beautiful figurines or pottery will please the eye for a long time.

To give clay products additional properties, they are subjected to high temperatures - firing. But the clay firing technology is quite complex and resource-intensive, so I will try to talk about some of the nuances that you may encounter.

Preparing for firing

Before firing the product, it must be thoroughly dried for 2 to 7 days, depending on the size of the product. It is necessary to dry the product away from heating devices, direct sunlight, drafts - that is, to exclude any sudden changes in the environment in which the product is located. At room temperature and in a dark dry, the product will dry evenly.

With uneven drying, the product may crack and its small parts will simply fall off. Insufficient drying will result in firing defects. It is impossible to dry the product.

After the product has dried, you need to carefully inspect it for cracks. If there are any, you can try to cover them with liquid clay, but this does not guarantee the safety of the product during firing. The best option is to prevent the appearance of cracks, and this is obtained with high-quality modeling and competent preparation of clay.

Be sure to check the sound of the whistle - if it disappears or becomes deaf, then it's not too late to try to fix it.

In some situations, during the drying time, a spider can settle in the products (there was a case when he chose one of my whistles), in which case he needs to be moved to a safe place .

The final stage of preparation will be grinding the product. When grinding, fingerprints, various crumbs and bumps may disappear, and the product will acquire a noble appearance. Grinding can be done with sandpaper of small numbers.

Conditions for firing

Temperature. The most important thing in firing is a gradual increase in firing temperature and gradual cooling of the product after firing. In the first two hours, the temperature should not exceed 400 degrees. The temperature range should be between 300-900 degrees Celsius. At lower temperatures, firing will be insufficient and the product will not acquire the necessary properties. At high temperatures, the product can be completely destroyed.

duration. Depending on the size of the product and the firing method, the duration of the process can vary from 8 hours to several days. Very small products can be fired in a short time.

The composition of the material. The firing technology largely depends on the composition of the clay. Natural clay has an admixture of sand and the less sand, the lower the firing temperature. In my practice, there were cases when purchased powdered clay at 750 degrees literally boiled and dried out in the form of a porous sponge. The product was completely destroyed. The composition of the clay should not contain stones and air. If the material is not homogeneous, a break will occur. Since materials of different densities will expand with temperature changes in different ways.

Modeling quality. The main requirement for modeling is the absence of air bubbles in the product. When the temperature rises, the air will expand and will seek an outlet, tearing the product. Therefore, when filling cracks and fastening parts of the product, exclude the possibility of the formation of air capsules.

Firing methods

Firing in a muffle furnace. There are several ways to fire clay products, but the most common is firing in a muffle furnace. This is an electric oven equipped with a temperature control mechanism.

Modern furnaces have automatic firing programs for products of various types, a window for viewing the status of products and other options. Another important characteristic of the muffle furnace is the volume of the chamber. Some swords have a cylindrical chamber in which only small items can be placed, and there are large kilns for firing pottery and sculptures.

Firing at the stake or in a non-electric oven. A rather non-trivial task, primarily due to the fact that there is no way to fully control the temperature. In addition, the stove is rarely heated for eight hours, and it is difficult to sit around the fire for a third of the day. However, if you are still going to - place the product in a container with sand - this will smooth out a sharp rise in temperature.

Roasting at home. A clay product can also be fired on a gas or electric stove, but I warn you - this is quite dangerous and the firing quality will still be far from ideal. To do this, you can take a cast-iron pan with washed dry river sand and put it on fire. From above, you need to carefully install the product and cover it with a fireproof container - a clay pot or pan. The process should be monitored and the room should be regularly ventilated so as not to cause overheating and oversaturation of the air with toxic gases.

Why roasting is needed

During the firing process, the clay gets rid of almost all moisture, so the product becomes much lighter. In addition, clay elements are sintered and turned into a single ceramic ingot, which is resistant to deformation and moisture penetration. Hence the need for roasting.

Fired products are ready for painting, and after painting they are ready for use.

It's important to know

After firing, the clay is not suitable for modeling, as it is no longer clay, but ceramics.

Firing can be done from several times, gradually increasing the temperature limit to achieve optimal results and gain experience.

After the main firing, the product can be coated with a special composition and fired again. When melted, the composition forms a glaze.

During the drying and firing process, the product can be deformed and eventually become smaller than planned. Therefore, when creating a product, it is necessary to take into account the composition of the clay and the purpose of the future product. Clay with a high sand content is less susceptible to compression.

During the firing process, organic compounds will burn out (especially in natural clay) - this can lead to unpleasant odors. It is necessary to be able to ventilate the room.

The readiness of the product can be determined by weight, color and sound. After firing, any colored clay turns red. If it turned black - the product overheated, if it did not change color - it was not burned enough. Fired products have a lighter weight and a sonorous nature. However, whistles during firing can completely lose their sound (irreparably) or, on the contrary, change.

In any case, proper firing of pottery can only be achieved with experience. So keep it up and good luck!

After drying the clay, water comes out of the product, but not completely. Despite the fact that the product has lost weight and has the color inherent in dry clay, water particles still remain in it.

In order to remove the remaining moisture from the clay product, it must be burned. At a high temperature, all the water will come out and evaporate and the product will become dense and solid. This is due to the fact that water particles reduce the density of clay. When all the moisture is evaporated, the constituents of the clay bind tightly to each other.

Types of firing

There are two types of firing:

Without direct contact of the clay product with the flame

The pottery comes into direct contact with the flame

The first method (without contact with fire) is required for heavy products, that is, those whose weight exceeds 1 kilogram, or the percentage of moisture after drying is only 4% or less. The rest of the products require the use of the second method - coming into contact with the flame.

In any case, before sending the product for firing, it must be carefully examined. If cracks are found, then they can be covered up, since the product has dried up after drying, but still remains quite plastic.

Firing technology

The maximum firing temperature is 960°C (exceeding 970°C is not allowed). The product cannot be immediately fired at this temperature, it must be raised gradually, smoothly, without jumps, by about 100 ° C per hour. Thus, in the first two hours, the temperature in the oven should reach 300°C and it should also be gradually raised to 500°C. It is 500 ° C that is a critical point - at this temperature even very well-dried clay products can crack. Still smoothly and gradually the temperature should be brought to 960 ° C. The viewing window must not be opened during firing.

Again, it is necessary to lower the temperature in the furnace gradually, without jumps. The rate of temperature decrease should not exceed 60°C per hour and only after reaching 400°C in the furnace, the rate of temperature decrease can be slightly accelerated. It is allowed to take out the finished product at 60°C, and if the product is covered with glaze - at 40°C. Moreover, finished products should be laid out in dishes specially prepared for this.

It should be noted that the firing process using this technology, depending on the feedstock (clay), lasts from 72 to 96 hours.

Other technologies

Of course, only real enterprises can burn clay using the technology described above. After all, only in order to "not open the viewing window", it is necessary that it at least be. Yes, and the temperature would be nice to measure something. And in order to raise or lower the temperature gradually and also smoothly, you will obviously need some kind of regulator similar to the same ball valve that will open or restrict the path to the furnace, for example, for gas or other fuel.

But what about someone who wants to simply mold a rectangular parallelepiped out of clay and burn it. Then raise above your head and proclaim: "I made a brick!"?

That's what "other technologies" are for.

Firing principle

After firing, the clay becomes ceramic, but this happens at a temperature of 500-900°C, that is, the clay must be placed in a place where it is at least 500°C. The duration of firing depends on the temperature - the lower the temperature, the longer it takes to fire the clay. But still, it will take at least 8-12 hours to fire the clay.

When the clay after firing has become ceramics, it can be additionally covered with glaze and fired again.

Roasting at the stake

In an ordinary fire, a temperature of 750 ° C can be reached, which is quite consistent with the temperature at which clay turns into ceramics.

When firing on a fire, the rules for firing in an oven apply, namely, the product must be fired in the same way, evenly from all sides. To do this, you can overlay the product with firewood and make a fire around it. In general, that's all! If you maintain a fire for 8 hours, and preferably even longer, then the product will be completely cooked and will be strong enough. The longer the firing takes, the stronger the finished product will be. Before making a fire, a clay product can be placed on some kind of elevation, otherwise all the heat may be on top of the product.

You can check the quality after firing by the color and sound of the finished product. If the product looks burnt, has reversed color, has black spots, the firing took too long. If, upon impact, the product makes a dull sound, the firing time was not enough and the product did not turn into ceramics, but remained clay.

Roasting under the fire

Usually, it is customary to fire clay in kilns specially designed for this, since clay firing requires compliance with certain technologies. However, clay can also be burned at the stake. Firing clay on a fire is less technologically advanced, due to the fact that it is more difficult to regulate the burning temperature of a fire than in a furnace, and it is also easier to achieve the desired temperature at which clay becomes ceramics in a special furnace. But you can burn clay not only at the stake, but even under the fire.

For firing clay under a fire, you should put the finished dried clay product in some kind of container - a tin can, for example, may be very suitable for this. Dig a hole and put firewood in it in such a way that it resembles a grate. Place the prepared containers (cans) with clay products in the cells of a lattice made of firewood. Fill the hole with coals so that they completely cover the containers (cans). To do this, it is quite possible to use coals from an old fire. Sprinkle a thin layer of earth on top. In general, the clay kiln is ready.

It remains only to make a fire on top of this pit and use it at your discretion, so to speak, for your pleasure. You can cook lunch and dinner or dry your clothes and get warm, you can even just look at the burning fire and relax - the stove works. With this technology, the stove continues to work even after the fire stops burning. For example, if the fire is extinguished late in the evening, then it should be sprinkled with earth and left until morning. At night, clay products will gradually and smoothly begin to cool down, which makes this clay firing technology even more technologically advanced than ordinary firing at the stake. In the morning, only ashes will remain from the coals with which the containers with clay products (tin cans) were filled, and the products themselves will become completely solid and ready for their further use.

Large items, such as jugs or wide plates, are unlikely to be fired with this technology, but it is very suitable for small items. It can be, for example, some souvenirs or jewelry, or it can be quite specific products - arrowheads, small gears or something else.

Dry the product before firing it. To do this, leave at room temperature in a shaded place, away from heaters and drafts - so that there are no temperature drops. After seven days, you can complete the drying process in the oven - leaving the door ajar, gradually raise the temperature to 200 degrees for two hours.

Ideally, the clay should be fired in a muffle furnace. Such ovens can be of various sizes, including compact ones that can comfortably fit even in a room. Small electric ovens can be used in workshops that are not very spacious. To burn the product in such a stove, increase the temperature by 200-300 degrees every 4-5 hours. When the maximum temperature reaches 1000 degrees, begin to gradually reduce it. Remove the craft only after it has completely cooled down. The firing time and temperature may vary depending on the type of clay and the size of the object.

If the product is not large and it is not afraid to spoil it, you can experiment and try to burn it on an open fire. Take two tin cans of different sizes. Poke a few holes in them with an awl. Put a clay object in one of them, put the second one on top. Place the jars with the product on a small brickwork and lay a fire around it so that the volume of firewood is approximately the same on all sides. Burn the product by adding logs. When the fire burns out and the coals cool down, you can get the craft.

What is it needed for clay firing? Yes, so that your product or craft is stronger and serves longer and pleases you. After firing, if possible, the product can be decorated with glaze, or you can simply paint with acrylic paints.
Roasting is a very complex process. Roasting is not baking pies in the oven. It is much more difficult and cannot be done in an hour or two. Yes, and ordinary kitchen ovens, and even more so microwave ovens (as many people think) are not designed for this. For firing, special muffle furnaces are used. In them, the temperature rises to 950-1200 degrees.
But before firing the product, it must be dried. That is, just fashioned can not be immediately put in the oven and fired. It must be left to dry for several days. All moisture should evaporate from it. Dry the product away from drafts, and not in the sun. Otherwise, it will dry unevenly and cracks may appear on it. Also, the product, with uneven drying, can “lead” and, for example, if it is a whistle, then after drying it may stop whistling well.
In general, there are many different nuances in working with ceramics. You can't describe them all at once. Their knowledge gradually accumulates with experience.
Yes, and clay is a kind of material. Clay great variety. They differ from each other not only in color, but also in plasticity, melting point, shrinkage, and many others. Speaking of shrinkage. Shrinkage is when an item decreases in size during drying and firing.
The product is placed in the oven already dried. During firing, the temperature in the kiln is raised gradually. On some they stop. All this is due to the fact that the product goes through several stages during firing, and at the same time complex processes take place inside it at high temperatures.
At the first stage, up to 300 degrees, the clay product loses its physically binding water, and the temperature at this stage is increased slowly. Let the remaining water evaporate. Otherwise, the product may break. Then, at temperatures up to 600 degrees, recrystallization begins. And here it is necessary to linger for 40-60 minutes. At the final stage, up to 850 degrees, you also need to linger. At these temperatures, sintering occurs. Only after sintering, the clay product will become strong, it will acquire the correct ceramic color. In a word, during firing, everything happens smoothly and slowly. It takes me almost 7 hours to do this.
But even after firing, one should not rush, and the furnace is not immediately opened, but allowed to cool down to about 200 degrees. Otherwise, with a sharp change in temperature, cracks will appear on the products.
And here is the final stage - opening the furnace. This long-awaited exciting moment brings great joy and other indescribable feelings. And having experienced it for the first time, it is clear that everything that was previous was not in vain. And modeling with a painful creative process, and slow drying and troublesome waiting during firing - all for good reason. And there will be a desire to pick up the clay again and again go all this way from a shapeless cool piece to the finished product.