Raku Is Not Just For Potters Anymore

The Raku technique has its origins dating back to the 1500’s in Japan. Historians feel it was probably developed by Koreans under Japanese rule but the circumstances remain a mystery. Raku is a firing process that has been primarily associated with pottery, but in the last couple decades, ceramists have increasingly explored and experimented with the technique with positive results. So positive in fact, that it has recently become very popular with those artists involved with cast-ceramics. The exciting thing about Raku is that no two pieces turn out exactly alike.

The primary difference with Raku and other (glazed) finishing techniques, is the firing process. Normally ceramics and pottery ware are loaded into a cold kiln and the temperature is raised slowly until it reaches a set maturity level usually controlled with pyrometric cones, or electronic controllers. This process can take anywhere from 8-24 hours to complete the heating and cooling cycle. The Raku technique requires the item be either pre-heated and then loaded in a hot kiln; or loaded into a cold kiln with a fast heating process. The ware is ‘finished’ when it is removed from the kiln after reaching temperature in as short a period as 15-25 minutes. Sometimes, some effects can take considerably longer, but most normally it is a fast firing process.
Temperatures are not controlled by cones but rather by the ‘experienced eye’. Raku firing is always done on pre-fired ware, or bisque – NEVER on greenware.

When the glaze is ready, it is in a molten condition. The items are then removed with the use of long tongs and gloves and then they are plunged into some form of combustible material such as dried grasses, leaves, shredded paper, straw, etc. Each type of material creates different effects on the finished piece.

There are two methods for doing this. One is called reduction firing. This is where the ware is placed in a container that can be closed which has combustible material in it, When the ware is ready it is placed in the container and then it is closed, causing the flammable material to consume all the oxygen creating a carbonized environment. After suitable time, the ware is then cooled and finally scrubbed to remove the layer of carbon. This process is often hastened by immersing the ware into water while still somewhat hot. Beware of thermal shock; however. Many pieces can crack and or break

The second method is allowing oxygenation. Instead of a closed container, the ware is placed in a pile of combustible material and the flames create unique designs on the ware. Some artists completely bury the ware, others just build up the materials around the sides. The artist often likes to watch the effect of the colors developing and removing the ware from the flames when they achieve a pleasing appearance.

One must be aware of the dangers of thermal shock. That is one of the reasons ceramists have steered away from the technique – because cast ceramics is often not as strong/thick as pottery. However, with some practice and observation, cast ware is often more successful than pottery. Both pottery and cast-ceramic ware can and do crack and/or break. Because Raku is an art form, it is common practice to glue pieces together and appreciate that flaw as part of the aesthetic appreciation.

Raku can be done with any clay body; however there are some clay formulas developed which are more compatible with this technique. Most glazes can work as well, however there are many on the market currently that give wonderful results. Potters have traditionally mixed their own glazes, but they are even enjoying the new paint products on the market.

Keep in mind that Raku items are not water safe, food safe, or very durable and should be used as accent/décor/art. Even though, throughout history, the Japanese have had Raku tea ceremonies, the ware is not food-safe by modern standards. The Raku Tea Ceremony involves making a tea cup for a guest and serving tea in it when done-A very artful experience and tradition.

Watch for more articles on this and other similar finishing techniques.