Firing clay at home. Firing clay using an artisanal method This is important to know
So reproduction actually follows from the presence of dishes after the BP. Cups, bowls, jugs for drinks, all of this will be missing in any case, no matter how much 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 outside of the product is dry, but moisture remains inside, it may explode during firing. It also explodes when there are rocks in the modeling clay. After firing, the clay acquires new qualities - strength, rigidity, durability.
At home, when not muffle furnace, products can be fired on a regular electric or gas stove.
IN this lesson we will use an electric stove.
Using a small frying pan and a cast iron pot to fire your clay products. Pour fine sand into the bottom of the frying pan to gradually heat it up. We place the figurine on the sand and cover it with a pot.
The heating temperature must be increased gradually. First, turn on the minimum heat for 30 minutes, then raise the temperature to maximum for 5-6 hours. Before removing the clay figurine, you must wait for it to cool completely.
Second option
At my dacha I had the opportunity to use the most primitive and unpredictable method - firing at the stake (special literature does not recommend this, since this wild method can ruin your work). I decided to conduct an experiment. I laid out a small double-sided brickwork (it’s better if you can lay it out on four sides and leave room for a closed hole to make it easier to light a fire). The height of my masonry was 4 bricks, but this is not so important, the main thing is that then it would be possible to cover this masonry on top along with the product and leave it until the fire completely extinguishes and cools down. And you need to place the product so that the coals do not come into contact with it. To protect products from contamination and mechanical damage when fired in an open fire (on a fire and in a kiln), 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, light a fire (only birch logs are suitable), then free central place for dried (this required condition for any firing!) of the 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 flares up (this is necessary for uniform firing). Control of a more or less gradual increase in temperature will be required. I heated the product in an electric oven and, using a warm mitten, transferred it to a warm place near the fire (to avoid temperature changes). If you place it cold, then don’t let the fire come close at the beginning of firing, let it warm up, then watch the temperature. When we cook kebabs, we protect the meat from the fire, but you don’t have to protect the clay, just let it gradually get closer to it, so that the product does not burst due to a sharp increase in temperature, and when the fire stops whipping up, you can cover the top with something fireproof (lid from a barbecue, a piece of old metal sheet, etc.). I had a rusty piece of roofing on hand, which we use to blow on the fire when starting it. Then you can leave it to burn out uncontrollably and cool. The entire burning process takes at least three hours, and it will also take a slow cooling time, so in the evening or running, nothing will happen (you need to watch the firing). The product must be heated on all sides, otherwise you will hear clicks from explosions (it is better not to sit children nearby, in case a fragment will fly off), this practice is possible with this method. Successful results are obtained with small-sized products, whistles, but you still have no guarantee that you will save each of them.
Clay products are a very exciting and interesting process, which allows you to reveal your imagination and talent. If you want your clay figures to not lose their shape for a long time, you need to dry them, and then fire the clay at home, following a certain technology. After all, the long service life of your products will constantly please you. All your figures are unique - they only resemble themselves.
Material composition
Clay can have different compositions. It directly affects the firing technology. Natural clay contains an admixture of sand. The following pattern stands out: the less sand is included in the clay, the lower the temperature should be when firing the products. There are situations when, when using powdered purchased clay, it boils at 750 degrees and then dries out. As a result, the product resembles a porous sponge. In this case, the clay figurine is usually destroyed.
The clay composition must be free of air and stones. Never use heterogeneous materials because an explosion may occur. Because the composition will include materials that have different densities, and they will each expand in their own way when the temperature changes. 
Natural clay is a material of natural origin and is often not subject to additional processing. In nature you can find clay of various colors, which depends on the presence or absence of certain elements. For example, clay acquires its red color due to the presence of large amounts of iron. And if there are small quantities of iron and titanium oxides in raw clay, then the white color of the material remains even after firing.
Preparing material for firing
Before firing the clay, it must be dried. You will spend about a week on this process, depending on the size of the product. It is recommended to dry it in places where there are no heating devices nearby and where direct rays of the sun do not reach. The best option is room temperature and a dark, dry place. This is where the product dries evenly.
If the clay is dried unevenly, cracks or chips may form on the product. If it is not dried enough, the products may have defects after firing. But it is impossible to dry out the clay.
When the product has dried, it must be carefully inspected to see if there are any cracks on it. If they are present, they can be masked with liquid clay, but this does not guarantee that the product will not lose its shape during firing. It is best to prevent cracks from appearing. This can be achieved, you just need to properly prepare the clay and sculpt the product with high quality.
The final stage of preparation is polishing the clay figurine. During sanding, fingerprints and bumps are removed, and as a result, the products acquire a beautiful and well-groomed appearance. Sanding is carried out using sandpaper.
Another important factor is the quality of the sculpting. Make sure that there are no air bubbles in the figure while sculpting. When the temperature rises, the air expands and seeks a way out, as a result of which the product will burst. When you seal cracks or fasten pieces together, do it very carefully so that air capsules cannot form.
Rules for firing at home
You can fire clay at home. First you need to dry the product and then fire it in the oven. In this case, you need to gradually increase the temperature over two hours to 200 degrees. Clay figurines can be placed in a frying pan or cast iron pot. It should be taken into account that it is impossible to do a full-fledged firing in the oven, because the temperature is insufficient, it cannot harden it, but only dry it.
How to determine if a product is ready?
Very easy based on color, weight and sound. If the color of the baked clay is black, then the figurine is overheated. If the color has not changed, then the product has not been fired enough. Fired colored clay should be red in color.
Clay firing technology
Clay kiln
The best option for firing clay is this is a muffle furnace . The temperature in this oven can be adjusted. It should be remembered that such a stove is very expensive and not everyone can afford to buy it. But there is no need to be upset, because it can be replaced with other good devices, for example, firing clay in the oven. Start firing the clay at 200° for 2 hours. Then gradually raise the temperature to 1000° over 6 hours. This temperature regime allows you to protect the clay product from stains and help maintain a uniform structure.
Clay firing can also be done in barbecue or brick oven . These species are a closed space characterized by a stable temperature. It is needed so that the clay product heats up evenly, and various defects do not form on it, such as spreading of the surface. The product that is being fired must be left until the fuel has completely burned out and the firebox has cooled down. The product should be in the oven for approximately 4 hours.
Firing a clay product over a fire is a very affordable option. It is used for firing small items. So, take the clay product and place it in a tin vessel, which you have previously heated and made holes in the sides. In most cases, the vessel is an ordinary tin can. Fire the product for about 8 hours, no less.
Fire clay impossible in the microwave . Such an oven can only remove moisture. Clay products, after you have air dried them, place them in the microwave for 3 minutes. This is done to make their condition better.
Temperature
The main rule in firing clay products is that you need to gradually raise the firing temperature and then gradually lower it, giving the product time to cool. At first (first 2 hours) the temperature should be no more than 400°. The firing temperature can fluctuate in the range of 200-1000° during firing. If the temperature is lower, the firing will be insufficient and the figurine will not have the desired properties. If the temperature is very high, then the figurine may collapse.
Duration
This process can last from eight hours to several days. This depends on the size of the product and the firing technology. If the figure is small, then this can be done in the shortest possible time.
This is important to know!
- Once the clay is fired, the product can no longer be changed.
- You can do the firing more than once, while gradually raising the temperature to achieve the optimal result and gain experience.
- Once you have completed the main firing, you can apply a special coating to the figurine and then fire it again. This coating will melt and form a glaze.
- When dried and fired, the figurines may become deformed and decrease in size. That is why, when creating a product, you should take into account the composition of the clay and its future purpose.
- If the clay contains a lot of sand, the product will be less subject to compression.
- Also remember that during firing organic compounds burn out, which in turn leads to unpleasant odors. Therefore, it is required that the room be ventilated.
To give clay products additional properties, they are exposed to high temperatures - firing. But the technology of firing clay 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. The product should be dried away from heating devices, direct sunlight, and 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 place, the product will dry evenly.
If the product dries unevenly, the product may crack and its small parts may simply fall off. Insufficient drying will lead to defects during firing. It is impossible to overdry 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 cracks from appearing, and this is achieved with high-quality sculpting and competent preparation clay.
Be sure to check the sound of the whistle - if it disappears or becomes dull, then it is not too late to try to fix everything.
In some situations, during drying, a spider may settle in the products (there was a case when it took a fancy to one of my whistles), in which case it needs to be moved to a safe place .
The final stage preparation will be polishing the product. When sanding, fingerprints, various crumbs and bumps can disappear, and the product will acquire a noble appearance. Sanding can be done sandpaper small rooms.
Conditions for firing
Temperature. The most important thing in firing is a gradual increase in the 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 items can be fired in a minimum amount of time.
Composition of the material. The firing technology largely depends on the composition of the clay. Natural clay contains an admixture of sand, and the less sand, the lower the firing temperature. In my practice, there have been cases when purchased powdered clay literally boiled at 750 degrees and dried out in the form of a porous sponge. The product was completely destroyed. The clay should not contain stones or air. If the material is not homogeneous, a rupture will occur. Since materials of different densities will expand differently with temperature changes.
The quality of the sculpt. The main requirement for modeling is the absence of air bubbles in the product. As the temperature rises, the air will expand and seek a way out, tearing the product. Therefore, when covering cracks and fastening parts of the product, eliminate the possibility of the formation of air capsules.
Firing methods
Firing in a muffle furnace. There are several methods of firing clay products, but the most common is firing in a muffle furnace. This is an electric oven equipped with a temperature control mechanism.
Modern ovens have automatic programs firing of products of various types, a window for viewing the status of products and other options. Another important characteristic of a muffle furnace is the volume of the chamber. Some swords have a cylindrical chamber that can only accommodate small items, while there are large kilns for firing pottery and sculptures.
Firing over a fire or in a non-electric oven. This is a rather non-trivial task, primarily due to the fact that it is not possible to completely control the temperature. In addition, the stove is rarely heated for eight hours, and it’s difficult to sit by the fire for a third of the day. However, if you do get ready, place the product in a container with sand - this will smooth out the sharp increase in temperature.
Firing at home. You can also fire a clay product on a gas or electric stove, but I warn you - this is quite dangerous and the quality of the firing will still be far from ideal. To do this, you can take a cast-iron frying pan with dry washed river sand and put it on the fire. You need to carefully place the product on top and cover it with a fireproof container - clay pot or pans. The process must be supervised and the room should be regularly ventilated so as not to cause overheating and oversaturation of the air with toxic gases.
Why is firing necessary?
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 transformed into a single ceramic ingot, which is resistant to deformation and moisture penetration. Hence the whole need for firing.
The fired products are ready for painting, and after painting, for use.
This is important to know
After firing, the clay is not suitable for modeling, since it is no longer clay, but ceramics.
Firing can be done several times, gradually increasing the maximum temperature to achieve optimal results and gain experience.
After the main firing, the product can be coated with a special composition and fired again. When the composition melts, it forms a glaze.
During the drying and firing process, the product may be deformed and ultimately become smaller than planned. Therefore, when creating a product, you need 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 turns black, the product has overheated; if it has not changed color, it has not been burned enough. Fired products have a lighter weight and a ringing nature. However, when fired, whistles can completely lose sound (irreparably) or, on the contrary, be transformed.
In any case, correct firing of clay products can only be achieved with experience. So go for it and good luck!