What is raku pottery
Raku ceramics - the joy of experimentation
Raku means "joy" and has its origins in Japan in the 16th century. It was conceived by the tea ceremony master Sen-no Rikyu and refined throughout his life. He managed to unite the spirit of Zen Buddhism and the tea ceremony interwoven with it. Classic raku values clear forms and structures, the simplicity reduces the objects to the essentials. The tea bowls created by this special distillation technique have the highest reputation in Japan. The well-known Japanese saying “ichi raku, ni hagi, san karatsu” (in German: one raku, two hagi and three karatsu) illustrates the importance of this cultural asset within the available tea utensils and the Japanese tea ceremony.
In the 1940s, raku slowly made its way into the western world, mainly through the artist duo Soldner and Leach. They broke up the classic Japanese raku tea culture, which thrives on minimalism, and introduced a diverse range of shapes and colors. Nowadays, raku ceramics are characterized by a high-contrast color change, low firing temperature and a short firing time.
Basically all types of clay and even porcelain raku can be fired. Almost all glazes with a low melting point can be used - but it is more a question of taste than a question of feasibility. The crux of it is that there are several pitfalls that are also located in different areas and demand concentration, imagination, planning security, ability and strength from the ceramist. Ultimately, raku can be understood as a pleasure in experimenting.
In the further course of the descriptions I will concentrate on a raku firing process that I have tried and tested and only digress marginally if necessary.
In the case of raku, the ceramics are taken out of the furnace while glowing yellow at more than 1000 ° C and exposed to the room temperature. When it is removed, the temperature drops by around 500 ° C within a very short time and the ceramics have to withstand that. This is almost the end of the manufacturing process, but in order for the factories to get there, you have to begin accordingly.
Which tone is right for raku?
There are innumerable natural tones and many more varieties can be found in the special mixes. A very hard-wearing clay is required for the raku ceramics. It should also be white, if possible with the addition of kaolin, in order to offer a nice contrast to the glazes and thus further underline the character of raku. Another question that you have to answer at the beginning is what you want to manufacture and, above all, how. It is, as you can imagine, a balancing act between the individual requirements and the purpose. In order to achieve the appropriate durability, chamotte is mixed in with the clay. Fireclay is nothing else than clay that has already been fired and then ground into small balls. In the clay mass, it gives this stability and holding points for the finer particles within the mixture. The chamotte balls are mixed into the clay in a wide variety of grain sizes and proportions. For built raku, a 25% fireclay content with a grain size of up to 0.5 mm is the method of choice and reliably delivers good results.
One can imagine that these particles are rough or sharp-edged and that the clay as a whole is more organic. If you build by hand, that's not a problem, you hardly notice it. However, the proportion of fireclay and the grain size become a problem when working on the turntable. Sandpaper is continuously sanded through the palms of the hands and fingers. For rotated raku you should be very well versed at the turntable on the one hand (this brings speed in processing) and on the other hand you should use a less firebricked clay. For this, 10% fireclay up to a grain size of 0.2 mm has proven itself. It's still not pleasant, but after 1-2 days of intensive hand care the biggest wounds have healed. Now that you have made the decision what you want to manufacture for the raku brand, the processing during production is the be-all and end-all.
Here, too, quality over quantity applies.
The manufacture of raku ceramics
When manufacturing building ceramics that are intended for raku firing, it is advantageous to have been working with clay for a while. On the one hand to know the techniques, possibilities and hand movements and on the other hand to know the limits of clay in general. After all, it is an organic material that is intolerable and can become so during production.
By and large, there are no limits to what you can imagine. However, you have to pay attention to one or the other. On the one hand, there is the wall thickness; 1 cm has proven to be a good measure. If you build thinner, you will have problems later when removing it from the 1000 ° C oven. The iron pliers used for this are not necessarily filigree or can be described as fine tools. There is a serious risk of simply biting through the raku ceramics with the teeth of the pliers. If you build thicker, there are two problems: thermal and weight. In the oven, heat should flow through all ceramics at the same time and heat up as evenly as possible. This also ensures that the glazes on the different pieces melt evenly, as they all get about the same temperature. The other point is weight. When the ceramics come out of the 1000 ° C furnace, you are wrapped in heat protective clothing, including a mask and thermal gloves - because it is still damn hot. The iron tongs have a certain weight of around 2-3 kg. If you then have to lift a 5 kg ceramic piece out of the oven, you have reached your limits.
So far I've only covered hand-made raku ceramics. It's not much different with rotated raku. However, the wall thickness can be less than approx. 0.5 cm. Turned ceramic is a more homogeneous mass due to the manufacturing process. By rotating the turntable, the particles within the clay were all aligned in the same direction. As a result, it is unlikely that there will be system-relevant stress cracks. Weight tends to be a drop stick here, but a negligible one. Due to the smaller wall thickness, significantly more volume can be created with the same initial weight. As a specific example, raku tea bowls are to be mentioned here. A hand-made one is thicker than a twisted one - with the same initial mass, more tea will fit into the twisted tea bowl. It is therefore easily possible to use less starting material and thus save weight.
The rule of thumb is: as thick as necessary, as thin as possible.
When the ceramics have completely dried in the air, they are put into the first firing, the biscuit firing. After this, the ceramics are ready for the actual raku technique, the raku band.
The glaze for the raku firing
The raku technique is different from other techniques, that's what makes it so special. It begins with the glazing of the previously stirred ceramics. Glaze is basically ground glass to which oxides and water are added. This mixture has about the consistency of cream and must be stirred completely and thoroughly before each use. The crystals and oxides contained in it settle very quickly and the water stands without "content" above the actual glaze. In some fires or projects, this is a desired effect, as you can achieve grandiose color gradients with insufficiently stirred glaze and also enhance the simplest form.
There are no limits to the imagination when it comes to glazing - but experience helps to avoid gross mistakes and leads to nicer results. The best color, however, is the black of the smoldering fire. It takes some imagination, because with raku everything that is free of glaze turns black. This contrast should by no means be underestimated as a design component. It is of course a matter of taste, but less is usually more. It is precisely this motto that characterizes classic raku and goes hand in hand with its origins, Sen Buddhism. The technique developed by Sen no Rikyū lives from reduction, minimalism and clear forms or structures. What you shouldn't forget is that there is another color in addition to the colors used. The drink is rarely completely colorless - sake is a good counter example.
The raku brand
Various types of firing (gas, electric or wood) can be used as raku ovens and all of them have their advantages, disadvantages and peculiarities. All of them have a large opening that makes it easy to put in and take out the ceramics. Likewise, in the event of a raku fire, occupational safety must always be observed. Long clothes made of cotton, thermal gloves, protective goggles, a woolen hat for the hair and, above all, a face mask (at least one FFP2 mask) should be worn. Due to the flying sparks that are taking place, you should also keep an eye on the surroundings and plenty of water should always be available.
After the raku oven has reached around 1000 ° C, it must be checked again and again whether the glaze has melted cleanly on all pieces. A trained eye is required, the secret is the shine! It's a very special one and once you've seen it, you know what I'm talking about.
Now to the real thing! The ceramics, glowing yellow, are taken out of the furnace with tongs. These are not grill tongs from the Sunday barbecue in the park. These are about 1 meter long iron pliers with small teeth and a capital dead weight. In order to prevent heat transfer as far as possible, they mostly still have wooden-sheathed handles. With these tongs you now reach into the oven and take out the tea bowls or other objects. They glow like lava because they are as hot as lava! In one go, the ceramics are placed in a barrel with sawdust or other easily combustible organic material. Some prefer leaves, others newsprint. Classically, however, wood shavings were used, as these were already present from the classic way in which the stoves were fired. The hot ceramics ignite the chips immediately and make everything soot and smoke.
The temperature drop that follows leads to the cracks (craquelé) in the glaze and ceramics that are typical for raku. This is exactly the reason why raku is so peculiar. It is not just a matter of sophisticated craftsmanship in production. The ceramics themselves are exposed to immense forces, the clay has to withstand this and it has to cushion the stress cracks in the glaze. As described, it depends immensely on the sound itself - you can hear it continuously cracking, crunching and cracking. As a comparison, the sound of an ice cube being doused with water is quite apt. This is the moment a raku pottery is born.
Raku was born out of fire, which is now smoldering and blackening all glaze-free surfaces and the cracks that have arisen. Finally, after cooling, the ceramics have to be scrubbed extensively with a rough sponge and steel wool, as the burnt organic materials are burned into the glaze.
Due to the history of its creation, raku ceramics have a strong smell after the fire and are not waterproof after the fire. The relatively low temperatures are not sufficient to crystallize the minerals contained in the clay. But raku wouldn't be a pleasure if there wasn't a pragmatic solution to this problem. It's time. Raku has its origins in Zen Buddhism, raku is born out of deceleration. The industrialized world is hectic enough. Enjoying a tea from a handcrafted raku chawan is like the world is on a break. So it happens that the chawan, vase or plate sintered over time due to the suspended matter contained in the tea or water and is absolutely waterproof after a while of use. At this point, the smell of fire, ashes and soot has long since disappeared.
As with everything in life - good things take time. At that time like today.
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