Raku ceramics - The joy of experimental work

Raku freely translated means "joy" and has its origin in Japan of the 16th century. It was invented by the tea ceremony master Sen-no Rikyu and refined throughout his life. He has managed to unite the spirit of Zen Buddhism and the tea ceremony interwoven with it. Classical Raku emphasizes clear forms and structures, the simplicity reduces the objects to the essentials. The tea bowls created by this special firing technique have the highest reputation in Japan. The well-known Japanese saying "ichi raku, ni hagi, san karatsu" (in English: 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 lived on minimalism, and introduced a diverse range of shapes and colours. Today, Raku ceramics are characterized by a high-contrast color change, low firing temperature and a short firing time.
In principle, all types of clay and even porcelain can be fired Raku. Almost all low melting glazes can also be used - but it is more a question of taste than of feasibility. The crux of the matter is that there are several pitfalls that can be found in different areas and demand concentration, imagination, planning reliability, skill and strength from the ceramist. In the end, Raku is to be understood as a desire to experiment.
In the following descriptions, I will concentrate on a Raku firing process that I have proven and only digress in the margins.
In raku, the ceramics are taken out of the kiln at more than 1000 °C and confronted with the room temperature. When they are taken out, the temperature drops by about 500 °C within a very short time and the ceramics have to withstand this. This is almost the end of the production process, but in order for the works to get there, you have to start accordingly.

What is the right clay for Raku?

There are countless natural clays and many more varieties can be found in the special mixtures. For Raku ceramics a very durable clay is needed. It should also be white, if possible with kaolin added, to provide a nice contrast to the glazes and thus further emphasize the character of Raku. Another question to be answered at the beginning is what you want to make and especially how. It is, as you can imagine, a balancing act between the individual requirements and the purpose. In order to achieve a corresponding durability, fireclay is mixed into the clay. Chamotte is nothing else but clay that has already been fired once and then ground into small balls. In the clay mass, it gives it stability and holds the finer particles within the mixture. The fireclay balls are mixed into the clay in various grain sizes and proportions. For built raku, a 25 % fireclay proportion with a grain size of up to 0.5 mm is the means of choice and provides reliably good results.

Mann knetet braunen Ton

One can imagine that these particles are rough or sharp-edged and the clay is more organic as a whole. If you build by hand this is no problem, you hardly notice it. However, the fireclay content and grain size becomes a problem when working on the pottery wheel. Sandpaper is continuously sanded through the palms and fingers. So for turned Raku you should be very experienced on the pottery wheel (this brings speed in processing) and use less chamotte clay. For this purpose, 10% chamotte up to a grain size of 0.2 mm has proven to be the best choice. It is still not pleasant, but after 1-2 days of intensive hand care the biggest wounds have healed. Now that you have decided what you want to produce for the Raku firing, the processing is the most important part of the production.

Here too, quality is more important than quantity.

The production of Raku ceramics

When producing build-up ceramics intended for Raku firing, it is advantageous to work with clay for a while. On the one hand to know the techniques, possibilities as well as handles and on the other hand to know the limits of clay in general. After all, it is an organic material that is grumpy with underneath and can become so with underneath during production.

On the whole, there are no limits to the imagination, what pleases can be built. But you have to consider one or the other. On the one hand there is the wall thickness; 1 cm has proven to be a good measure. If one builds thinner, there will be problems later when taking it out of the 1000 °C hot kiln. The iron tongs used for this are not necessarily filigree or fine tools. There is a serious danger of simply biting through the Raku ceramics with the teeth of the pliers. If you build thicker, two problems arise: thermal and weight. In the kiln, heat should flow through all ceramics equally and heat up as evenly as possible. This also guarantees an even melting of the glazes on the different pieces, as they all get about the same temperature. The other point is the weight. When the ceramics come out of the 1000 °C hot kiln, 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 about 2-3 kg. If you now have to lift a 5 kg ceramic out of the kiln, you will reach your limits.

grauer Teller auf der Drehscheibe

So far I have only dealt with handmade Raku ceramics. The Raku with wheelthrown ceramics is not much different. However, the wall thickness can be undercut, down to about 0.5 cm. Wheelthrown ceramics are a more homogeneous mass due to the manufacturing process. Due to the rotational movement on the pottery wheel, the particles within the clay were all oriented in the same direction. It is therefore unlikely that system-relevant stress cracks will occur. Weight also tends to be a falling stick here, but a rather negligible one. Due to the lower wall thickness, significantly more volume can be produced with the same initial weight. Raku tea bowls are a concrete example. A hand-made one is thicker than a wheelthrown one - for the same initial weight, even more tea will fit into the wheelthrown tea bowl. It is therefore no problem to use less initial mass 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 placed in the first firing, the biscuit firing. After this the ceramics are ready for the actual Raku technique, the Raku firing.

The glaze for the Raku firing

The Raku technique is different from other techniques, which is what makes it so special. It begins with the glazing of the previously fired ceramics. Glaze is basically ground glass which is mixed with oxides and water. This mixture has roughly the consistency of cream and must be stirred completely and thoroughly before each use. The crystals and oxides contained in the mixture settle very quickly and the water stands without "content" above the actual glaze. For some firings or projects this is a desired effect, because with insufficiently stirred glaze you can achieve grandiose colour gradients and enhance even the simplest form.

There is no limit to your imagination when glazing - but experience helps to avoid gross mistakes and leads to more beautiful results. The best colour, however, is the black of the smouldering fire. It requires some imagination, because with raku everything that is free of glaze turns black. This contrast should not be underestimated as a creative component. It is of course a matter of taste, but less is usually more. It is precisely this motto that distinguishes classical raku and goes hand in hand with its origin, Sen Buddhism. The technique developed by Sen no Rikyū lives from reduction, minimalism and clear forms and structures. What should also not be forgotten is that in addition to the colours used, there is also one more. The drink is rarely completely colourless - sake is a good counterexample.

Keramik-Kartell - Glasieren

Der Raku-Brand

As a Raku kiln, various types of firing (gas, electric or wood) can be used and all have their advantages or disadvantages and peculiarities. What they all have in common is a large opening, which makes it easy to put in and take out the ceramics. Likewise, occupational safety must always be taken into account during raku firing. Always wear long cotton clothing, thermal gloves, safety goggles, a woollen cap for the hair and above all a mouth guard (at least a FFP2 mask). Due to the flying sparks, the surroundings should also be kept in view and water should always be provided in abundance.
After the Raku kiln has reached a temperature of about 1000 °C, it must be checked again and again whether the glaze has melted out cleanly on all pieces. A trained eye is necessary, the secret is the shine! It is a very special one and once you have seen it, you know what I am talking about.

Now for the real thing! The ceramics are taken out of the kiln with a pair of tongs. These are not grill tongs from the Sunday barbeque in the park. They are about 1 meter long iron tongs with small teeth on them and a capital dead weight. In order to prevent the heat from being transferred, they usually have wood-covered handles. With these pliers you reach into the kiln 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 newspaper. The classic way, however, was to use wood shavings, as these were already available from the classic firing of the kilns. The hot ceramics ignite the shavings immediately and cause everything to soot and smoke.

The subsequent drop in temperature leads to the cracks (craquelé) in the glaze and ceramics typical of raku. This is exactly the reason why Raku is so unique. It does not only depend on mature craftsmanship during production. The ceramics themselves are exposed to immense forces, the clay has to withstand this and it has to cushion the stress cracks of the glaze. As described, it depends immensely on the clay 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 when a Raku ceramic is born.

Raku is born of fire, which now smoulders and blacks all glaze-free surfaces and the crackles that have formed. Finally, after cooling down, the ceramics still need to be scrubbed extensively with a rough sponge and steel wool, as the burnt organic materials are baked into the glaze.

Due to its history, Raku ceramics smell strongly after firing and are not waterproof after firing. The relatively low temperatures are not sufficient to crystallize the minerals contained in the clay. But Raku would not be happy if there were no pragmatic solution to this problem. It is time. Raku has its origin in Zen Buddhism, Raku is born out of deceleration. The industrialized world is hectic enough. Enjoying a tea from a handmade Raku Chawan is like the world having a break. This is why the Chawan, vase or plate sinters over time due to the suspended particles contained in the tea or water and after a while of use is absolutely waterproof. By this time, the smell of fire, ash and soot has long since disappeared.

As with everything in life - good things take time. Then as now.