Naked Raku - naked on the kiln?
No, of course nobody is naked at the kiln during Naked Raku! We put on thick clothes and pay attention to occupational safety - especially face and breathing protection is essential! The ceramics are taken out of the kiln at more than 1000 °C, yellow-glowing. Please also pay attention to your work protection and do not take it lightly.
Now we make the ceramics naked!
A small insight into the history of the Raku
Raku (jap. 楽焼, rakuyaki) is an old Japanese firing technique and is popular all over the world. The technique developed in the 16th century is based on Wabi Sabi, the concept of beauty at the blemish, and Buddhism with its approach of minimalism. The non-Japanese and roof tile maker Chōjirō is considered the inventor of the raku. He invented the technique under the direction of Sen no Rikyū, a tea ceremony master. The importance of this Japanese cultural asset for the Japanese is made clear by the Japanese proverb "Ichi Raku, ni Hagi, san Karatsu" (one Raku, two Hagi, three Karatsu). The Raku technique is still a pillar of Japanese ceramics today.
Raku arrived in Europe around 1940 with the two British ceramists Soldner and Leach. They had discovered the technique on one of their journeys in Japan and changed the traditional raku somewhat. It was probably a little too archaic and minimalist for western tastes. In this way they created the "Western Raku" which is still enjoying increasing popularity today and creates enchanting Raku ceramics.
Western Raku, the basics
Raku ceramics are usually made from a very white, high firing clay. It also contains a lot of chamotte and sand or pumice and is not very bricked. This lean clay also contains little lime and is usually mixed with talcum and lithium oxide. This makes it less plastic, but has the advantage that it is very robust, has little chipping and offers a beautiful black and white contrast.
With Raku and especially with Naked Raku the ceramics are made a little thicker than it seems necessary at first. However, the ceramics must not lose too much heat when removed from the kiln, otherwise stress cracks will occur within the clay.
The rapid drop in temperature demands everything from the ceramics
After firing the ceramics in biscuit firing, they are glazed with a raku glaze and fired in raku glaze firing. This is very quickly heated up to approx. 1000 °C. This is usually done with a gas burner, as wood can do a bit more and above all requires supervision. When the temperature is reached and the glazes have melted out, the yellow-glowing ceramics are taken out of the kiln at more than 1000 degrees Celsius.
The pliers used are instruments that weigh a good 3 kg and have been tried and tested with teeth, and cannot exactly be described as filigree. However, the raku is made a little thicker, so that the iron pliers cannot harm the ceramics. When removing the ceramics, they are placed in an organic material (leaves, sawdust, grass cuttings). The heat causes the ceramics to immediately ignite the sawdust that is usually used, and a smouldering fire develops in the metal pots. Due to the strong smoke development it is advisable to do raku only outdoors and, if necessary, to have the forest fire stages in mind. Flying sparks cannot be avoided with raku!
The oxygen deprivation in the pots during smouldering firing causes a chemical change within the glazes. Thus an azure glaze turns copper red due to the removal of oxygen from the copper. The smoke of the smouldering firing finds the crack, no matter how small, within the glaze and the carbon from the organic materials settles into the cracks of the glaze - an unmistakable craquelé is created and makes every Raku ceramic unique. Organic impressions are a special highlight. These sometimes happen when they meet the still soft glaze, rarely a pincer print can be found.
Only the glaze should crack
Raku glazes are low melting frits, which, mixed with oxides, have a wide colour spectrum. The smouldering firing in the sawdust colours all unglazed pieces on the ceramics into a silky matt black. The unique craquelé, on the other hand, comes about through cracks in the glaze, because the soot finds every crack, no matter how small. After approx. 45 minutes of smoking in the sawdust, the ceramics are ready to be removed and can be scrubbed thoroughly with a rough sponge.
So much for the "western raku". If you want to know more about it than this short overview, we have accompanied a raku firing for a day and in another article we give you useful tips and tricks for the raku. Now to the Naked Raku.
Naked Raku
Naked Raku has its name because it is naked raku. This is because the glaze flakes off and leaves the beautiful black crackle on the ceramic itself!
With naked raku, the ceramics are also made from a clay that is as white as possible, i.e. containing kaolin, and are built a little thicker. During the manufacturing process, special attention must be paid to the surface of the ceramics. This must be as smooth and even as possible. It is best to polish it with a tumbled stone or to grind it evenly smooth after biscuit firing with very fine sandpaper. Here it pays off to be fussy and to polish and grind for 10 minutes more.
The separation engobe
Ceramic engobes are classically clay containing metal oxides. In red engobe, for example, the clay is mixed with iron, in black engobe the clay contains manganese. With naked raku, the beautiful black crackle effect is especially accentuated by the contrast to the white clay. Because of this, the separation engobe must be free of oxides and other colour bodies as well as chamotte. It is mostly a thick measure and every raku ceramist has his own recipe. We have found that a quartz/kaolin mixture works best for us. Theoretically, it is possible to use viscous slurry of white clay. The separating engobe is elementary in Naked Raku and without it it is not possible, because it is the protective layer between the ceramic and the glaze. The smoothly polished ceramics are wiped clean with a damp sponge and dry again in about 15 minutes. Now the separating engobe is generously applied to all areas that will later be white. This can be done by brushing, dipping or pouring over. There is no "too much" when using Trenn-engobe, but it should be remembered that the soot in the sawdust must still be able to reach the ceramic when firing. Then it has to dry again.
The Naked Raku Glaze
In theory, any glaze can be used to glaze naked raku, because the separation engobe makes it flake off again. However, the fact that the glaze has to crackle for a beautiful Naked Raku speaks against this, because only then can the soot from the smouldering firing in the sawdust reach the ceramic. Another point to consider for a separate naked raku glaze is that dust and separating engobe get into the glaze when the ceramic coated with separating engobe. These impurities cause the glaze to lose its brilliance and over time it becomes blind and even dull.
Therefore, it makes sense to produce or apply your own Naked Raku glaze. For the glaze we usually use gerstleyborate and nepheline syenite, which we prepare 1 + 1. However, there are an endless number of glaze recipes and it is a matter of taste which one you want to use. When making a glaze, it is important to make sure that you do not make too much. This mixture tends to crystallize after about a week and is then no longer usable, what a pity. It is not necessary to use large volumes when glazing Naked Raku ceramics, because the glaze does not have to be applied properly or evenly. As it flakes off again, you can really mess around. Now that the ceramics have been treated with separating gobe and naked raku glaze, they need to dry thoroughly. It is advisable to glaze the day before for raku firing or to leave the ceramics to dry in the kiln at around 60°C for a few hours.
The Naked Raku firing day
With the Naked Raku the firing day hardly differs from the normal raku. The ceramics are also removed from the kiln at 1000 degrees Celsius and placed in organic material. Sawdust is particularly suitable because it is easy to obtain and easy to dose. As with the normal raku, the glaze gets stress cracks and forms a beautiful craquelé. After the ceramics are now in the sawdust, Naked Raku separates from the normal Raku. Because the ceramics are taken out after about 10 minutes! It gets tricky and now requires a lot of dexterity, because water comes into play. The ceramics, which are still a good 700 °C hot, are now placed on a clean, heat-resistant surface and are first carefully sprayed with water. This extreme difference in temperature causes the separating gobe to burst from the ceramic like an eggshell from a hard-boiled egg. Shards of the engobe/glaze flow down the ceramic like scales. After the ceramic has cooled down a little, you can wash the rest off with plenty of water. But be careful, the scales are sharp-edged and cut at the slightest touch like small sharp ceramic knives.
Cleaning and polishing of Naked Raku ceramics
Now it can be seen whether good polishing was done during production and the meticulousness pays off! The smoother the surface of the ceramic, the more difficult it is for the separating gobe to penetrate into the pores and get stuck. With well polished surfaces, it is sufficient to wipe over them with a clean sponge. In most cases, however, you will have to scrape off the ego board with a modelling stick or something similar. Metallic objects should be avoided, as they leave unsightly grey streaks on the white surface and cannot be removed.
The finishing
Finally, the clean and above all dry Naked Raku ceramics are rubbed with beeswax polish and polished. This treatment gives them a silky shimmer and makes them more resistant. We have made the production of the Raku polish available to you in one of our blog posts.
Basically no Raku ceramics are waterproof and therefore not frost-proof. However, with tea bowls and other dinnerware this is usually not a problem. The suspended particles contained in the tea water quickly seal the few open channels within the craquelé and thus make the tea bowls watertight. Vases and the like can be sealed within 12 hours with a sealing agent - but this is not suitable for dinnerware! Generally speaking, Naked Raku is conceivable for dinnerware, after all it is only clay and charcoal. However, it is less hygienic than normal raku because of the open pores and the surface not sealed with glaze. As garden ceramics both are suitable, as long as they are stored frost-free in winter and the surfaces are sealed with Naked Raku.