The Magic of Raku
Would you ever think of opening your kiln to remove items when they are bright red and glowing? While that may sound a little crazy, it is actually part of the exciting process when creating Raku.
By combining the proper clay with colours and special firing technique you can achieve stunning results and colours not obtainable by any other process. Opening a kiln while it is hot may not be what you are used to doing, but with simple precautions Raku can be a safe and addicting technique you will want to repeat. Once you get started it is hard to stop.
The basics
The final results of Raku may appear to require some super artistic talent, but it is something even the artistically challenged can successfully complete. Starting with a bisque shape, it is first glazed and then fired. When the kiln reaches the proper temperature, it is opened and the object is removed with special tongs. The red-hot piece is then placed in a container filled with combustible materials and covered. After a period of time, the creation is removed and can be cooled in water. It really is simple and requires no special painting techniques.
Creating a piece
Pieces for Raku can be constructed with a slab of clay, thrown on a wheel, clay puzzled or cast in a mold. Some low-fire and high-fire clay bodies will work, but it is best to use clay or slip specifically made for Raku. The shock of being removed from the kiln and placed in cold water can cause some pieces to split or shatter. Raku clay is specially formulated to withstand the drastic temperature changes.
Finishes
Many colour manufacturers have special Raku glazes. Some come in a premixed formula while others are dry and need to be mixed with water. Formulas for creating your own finishes are also available. Most people think they can only use low-fire colours made specifically for Raku. However, many low-fire and even some high-fire finishes will give stunning results. It really depends on what kind of look the artist wants to achieve. Some anticipate the flashes of red, purple, copper and other metallic looks. Others look for crackle finishes and more subtle tones.
While it is impossible to ever get two items to turn out exactly the same, experimentation is the best way to discover the unique things that happen to colours when Raku fired.
Firing
Special kilns are made for Raku firing, but almost any kiln will work. Some Raku kilns are gas fired while others are electric. The main advantages to gas kilns is they can be fired almost anywhere, even without electricity. And since you probably want to do this firing outdoors, these gas (propane) kilns are the most convenient. Many of the special gas Raku kilns will heat more quickly then some electric kilns similar in size.
Many Raku kilns are also designed with a pulley system where the walls and top of the kiln are lifted, exposing all ware inside the chamber. This makes it much easier to grab hot items with tongs. With top-loading kilns, the artist reaches down in to the hot chamber with all of the heat coming directly up. With larger Raku kilns, shelves can be used to create layers of ware. With a top-loading kiln it is virtually impossible to safely remove shelves to get to items below, limiting you to one lay of items being fired at one time.
Electric kilns also work for Raku firing. Many small kilns will plug right into a standard outlet so they can be moved outdoors during the firing process. Many electric Raku kilns have the same pulley system as their gas counterparts, offering the same advantages. Just make sure the kiln you select will reach the desired temperature to bring the selected finishes to maturity level. Always make sure the kiln is unplugged before reaching inside with the metal tongs to remove ware.
Combustible materials
A metal trash can or a metal pail with a lid work great for a chamber where the combustible materials are placed and used to hold the hot ware. Since the pieces will be over a thousand degrees when placed in the chamber, the container needs to withstand fire and high heat.
A variety of combustible materials work and each can give slightly different effects to the final product. One of the most common is shredded paper. Shredded newspaper gives a different look than shredded junk mail. Sawdust, grass clippings and straw will all work as well. Since two items rarely turn out identical in the Raku process, it is difficult to say any one material will give a certain result. Experimentation with different materials or combinations is recommended.
Once the hot piece is removed from the kiln, it is placed in the container with combustible materials below the item, with more being placed on top before the lid is put in place. The time it takes to get the item in the container and covered will affect the final finish. You will generally want to do this as quickly as possible. Most materials will also ignite rather quickly and placing the lid on the container will smother the flames.
The length of time the pieces remain the combustible materials will also affect the final finish. Some artists leave ware in for only a few minutes while others leave items for long periods. Again, with all the variables involved with this process, experimentation is recommended.
Cooling
After you determine how long the items need to remain in the combustible materials, carefully remove them. Remember the container will likely be very hot and once the lid is removed the combustible materials may ignite again and flame up. The object will still be very hot, so use the tongs to remove it and dip it into a bucket of cold water or douse with cold water. This will freeze the finish and stop the colours from changing. Make certain the container you select for water is wide enough to fit the ware inside. Plastic pails are ideal but can melt if the hot ware touches the sides. Other artists will allow the items to remain in the chamber until it is completely cooled. Play around with the options and see what works best for you.
Safety
Raku is a really fun technique requiring safety precautions. Wear protective gear, like gloves designed to withstand the high temperatures. Hot mitts from your kitchen may not do the trick.
Check with your ceramic supplier for the proper clay, tongs, kiln, hand protection and even eye protection.
Some new to Raku may not think of the rest of their body. Protect long hair by wearing a hat. Cover your arms with long sleeves even if you are working in the summer. Avoid loose-fitting clothing since baggy sleeves can come in contact with hot ware or surface. Polyester is not the best choice for clothing fabric. Also protect your feet. If you happen to drop a hot item you do not want it hitting bare toes sticking out from the sandals.
The work area is also something to take in consideration. Keep flammable materials you do not want to ignite away fromyour work. Use extra caution when removing items from the kiln and combustible materials container.
Always unplug an electric kiln before trying to remove pieces. If the metal tongs come into contact with an element you may be in for a big shock.
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