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Processes Used By Leib 

Creating the Wares

Leib Creates some pieces by hand (critters, for example) and forms others on her wheel. In some cases, Leib does additional sculpting or carving on her wares before firing them. 

Click here to see the evolution of a bowl as it is turned on the wheel.

Bisque Firing

The Bisque firing is the first firing for both the Stoneware and Raku processes. The purpose of the Bisque firing is to remove the real and chemical water from the clay piece and to harden it to a still-porous state. 

In the Bisque firing, the ceramic pieces are placed in the kiln and the temperature is slowly raised to boil off the real water still in the piece. During this process, the piece first expands slightly and then contracts as the water is removed. 

As the temperature increases, the chemical water begins to burn off. This effect is completed by the time the kiln reaches 1100 degrees F. The firing continues until cone .07 or .06 is reached, at which time the kiln shuts itself off. The kiln is allowed to cool down before being opened. 

When the Bisque firing is complete, the ceramic pieces have lost as much as 12% or their original volume. After the Bisque firing, the glazes are applied. The glazes adhere by being slightly absorbed into the surface of the still-porous piece. the pieces are now ready for either the stoneware or Raku firing.

Examples of Bisque-fired Wares

Electric Kiln                Stacked Wares inside kiln

Leib uses the electric kiln for Bisque firing and for Stoneware final firing. 

Raku Process

The Raku process originated in Japan in the 16^th century. The process is named for the Japanese family that was most prominent in its development.  In the USA, the process was modified to take advantage of American firing techniques and the chemical properties of the glazes under stressful fast firing and thermal shock conditions.  

In the Raku process, glazes are applied to the Bisque-fired ceramic piece, which is then placed in the Kiln and brought to an optimal firing temperature very quickly. When the glazes are melted and shiny in the Kiln (approximately 1800 degrees F), the piece is removed (with tongs) and placed in a combustible material such as wood chips or dry leaves. The material immediately bursts into flames from the heat of the piece.

Gas kiln Leib constructed for her Raku firing

The removal of the ceramic piece from the kiln when the piece is red hot causes the thermal shock. Before smothering the ceramic piece in combustible material, the ceramist may elect to enhance the shock by briefly plunging the piece into cold water. This causes the glaze to crackle into wonderful, unpredictable patterns.

 Smothering the ceramic piece in combustible material subjects the piece to a “reduction” environment in which the burnable material is starved of oxygen and smokes heavily. The smoke blackens the piece wherever there was no glaze and wherever the glaze crackled.  The piece is then allowed to burn in the open for a few seconds, after which it is again smothered in the combustible material. Then the piece is removed from the combustible material and sprayed lightly with water. This rapid cooling process seems to bring the metallic elements in the glaze to the surface and creates the incredible luster for which the Raku process is known. Finally, the ceramic piece is placed in a tub of water to cool and to loosen the burnt material still on the piece.

Click here to see the glazing and firing process.

After the final cleaning process, you first get to see the full beauty of the glaze. The wonder of the Raku process is that you never know exactly what the final ceramic piece will look like until you clean it off after the firing process. So many variables enter into the final result: 

In any case, a Raku piece that is created with care is a unique and beautiful object to be dearly treasured by the one who eventually comes to possess it.

Stoneware Process

In the Stoneware process, glazes are applied to the Bisque-fired ceramic pieces, which are then stacked in the Kiln and brought to a high firing temperature (about 2200-2400 degrees F) over a 24 hour period. The kiln is fired and then left to cool down over another 24 hour period. At the end of the cooling down period, the kiln is opened and the cooled ceramic pieces are removed. Note that more pieces can be fired at a time than with the Raku process because the pieces are cool when taken out of the kiln, and no more processing is required.

Stoneware ceramic pieces can be used as cookware, and can be cleaned in a dishwasher. Raku pieces must be carefully hand-wiped and cannot be used in the oven or cleaned in a dishwasher. (Raku pieces are, with the exception of jewelry, primarily for display purposes.)