Reduction Cooling Ceramics

Relies on carbon monoxide not carbon produced by a small reducing flame in the kiln as it cools.

Reduction cooling ceramics. Reduction cooling in a fuel kiln maintaining slight reduction atmosphere during cooling cycle from maturing temperature down to approximately 1400 f in order to minimize reoxidation of clay and or glazes. The oxidation process for example can alter the color of the glazes or paint you ve chosen to use. At high temperatures this produces carbon monoxide gas which will steal loosely bonded oxygen from other materials in ceramics mainly iron and copper. Crystals of alpha quartz turn to beta quartz between 1022 1063 f and the reverse occurs during cooling over the same temperature range.

Reduction causes most ceramic materials such as your glazes to melt faster. If the firing has been in oxidation the reducing flame will affect only the surface. A reduction atmosphere occurs when the amount of available oxygen is reduced. Dunting is caused when a ware is cooled too quickly past the temperatures at which silica undergoes a shift in crystalline structure from beta back to alpha.

These processes result in the metals in your glazes gaining electrons which means the net charge or oxidation state is reduced. A porous ceramic can absorb water by touching points of human body and in turn the evaporated water would. Salt firing soda firing. If the clay and glaze have been reduced on the way up reduction cooling prevents reoxidation.

Reduction firing reduction is firing where the kiln atmosphere has insufficient oxygen for complete combustion more fuel than air to burn it. Clay tools equipment. As small carbon particulates build up on pottery surfaces they begin to aggregate as soot and oxidize causing a small flow of electrons into the ceramic surfaces. The cool ceramics lower the body temperature by contacts to its key points such as hands feet palms.

Reduction cooling produces some amazing surfaces in wood fired ceramics as seen in the following pieces by jonathan cross and mitch iberg. Johnathan cross vessel from the firebox kiln akagama mitch iberg clay tests from the firebox kiln akagama reduction cooling when overdone can create some less than desirable surfaces as seen below from the idyllwild ceramic arts wood fire kiln april 2003.