This is next section talks about Raku as a Technique
“Raku is a pottery technique that has it's origins in 16th century Japan. We are pretty sure that it was
developed by Korean potters under Japanese rule but the exact circumstances of it's development and in
what context it was discovered is a mystery. The raku technique, like other pottery techniques such as
salt glazing and pit firing, primarily revolves around it's firing process although involvement with raku
often goes much deeper into its philosophy, roots, and cultural significance. Traditional raku and our
western version of raku are similar in many ways though there are some significant differences.
To briefly describe the raku process we must understand that most all other types of pottery are loaded
into a cold kiln where the firing proceeds slowly until the desired temperature is reached. This firing
cycle may take anywhere from 8-24 hours or even longer. When the kiln has reached temperature
(which is generally determined through the use of pyrometric cones), it is shut off and allowed to cool
enough to be able to remove the ware using bare, or lightly gloved hands. The cooling cycle may last
from 12-24 hours or longer. The ware is considered finished when it is taken from the kiln. In raku, the
pieces may be loaded into a cold kiln but are often preheated and loaded into a hot kiln. The firing
proceeds at a rapid pace with the wares reaching temperature in as short a cycle as 15-20 minutes
(though raku firings can last up to several hours depending on the individual pieces and their firing
requirements). Glaze maturity is judged by the trained eye without the use of cones or measuring
devices. When the firing is determined to be completed the wares are immediately removed from the
kiln. Since at this point the glaze is molten, tongs or other lifting devices are used.
This is the stage in the process where traditional and contemporary raku differ in technique and
treatment. In our western version the wares are now treated to a 'post firing reduction' phase. The wares
are put into a container with combustible material such as sawdust, or leaves and allowed to smoke for
a predetermined length of time. The carbonaceous atmosphere reacts and affects the glazes and clay
and imparts unique effects and surfaces to the wares. Some of these effects are metallic and crackled
glazes surfaces and black unglazed clay. When the wares have cooled, they are washed with an
abrasive cleaner to remove all residue of soot and ash.” -CeramicsToday
About your Raku Ceramic
(Made by David W Riccio)
Your ceramic was made from a special clay designed to withstand tremendous thermal shock. The ceramic was constructed from wet clay, dried, and then fired in an electric bisque kiln to set the clay body and remove the chemical water from the clay body. The ceramic was then glazed with glazes designed for the Raku firing process. The glazed ceramic was then fired in a outdoor gas fired kiln to a temperature of 1850 degrees. While the ceramic was still at high temperature it was removed from the kiln and placed in a container full of combustible materials (paper, sawdust, etc), the container was allowed to catch fire and quickly covered to extinguish the flames and seal the container. This allows the ceramic to cool in a oxygen free (reducing) atmosphere. This causes the Raku glazes to reduce and produce a wide range of colors only obtainable in a reducing atmosphere.
When the ceramic has cooled sufficiently to allow it to be removed from the reduction container it is then either allowed to finish cooling in the air or is quickly cooled in a water bath. This ensures the glazes will be completely color set.
The ceramic is the cleaned with a stiff brush and soapy water to remove any surface soot and carbon. Any part of the ceramic that did not have any glaze will have absorbed carbon from the combustion chamber and it will be chemically bonded to the clay body (and will be permanently black). When the pot has dried after cleaning, I apply a protective coating of synthetic “wax”. The “wax” is an acrylic which polymerizes on drying to provide a thin protective non yellowing coating. The acrylic is resistant to water or acidic solutions but can be removed by washing the ceramic in a high pH solution like a strong soap, ammonia, or soda (baking soda in water).
I recommend that you use your ceramic for decorative (art) uses but it can be used for dry storage and where applicable for storage of kitchen utensils, knitting needles, etc. These ceramics are not suitable for use as water filled vases without the use of a glass insert. These are relatively low temperature fired ceramics and the clay body has not vitrified so water will eventually move through the clay body if it is stored in the vessel (the clay body is still porous).
I do not recommend the use of these ceramics for food uses as the glazes on many of them contain metals such as tin, copper, zinc, iron, and silver. The acrylic will provide some level of protection for dry food stuffs but they should not be used for wet foods or liquid storage.
For cleaning, I recommend washing in a water bath and or with vinegar as this will preserve the acrylic coating on the ceramic. Allow the ceramic to air dry, They should not be washed in a dish washer as this will remove the acrylic coating.