Ceramic and Soot
Zichen Xu
Award: Top 100
School: keystone academy
Teacher: ritah kendi
Category: Contrived
Photo #19498
Ceramic and Soot
I shaped this dark teapot and the cracked furnace with my hands, before subjecting them to a myriad of changes through heat.
The blackened surface of the purple clay teapot resulted from two distinct phases: the initial firing in the wood kiln and the subsequent daily use over firewood. Through the combustion of wood, the kiln achieves a temperature of 800 to 1200 degrees, which vitrifies the clay. In the vitrification, the teapot is in reduction, this process promotes the iron's ability to form complexes with carbon from subsequent use, iron-rich composition enhances, making the purple clay teapot darken. This initial firing prepares the teapot's microstructure, increasing the capacity in clay to absorb external substances.
In its daily usage, the teapot boils over wood fires, which release tar aerosols and soot particles due to incomplete combustion. These carbonaceous residues adhere to the teapot's porous surface through capillary action and accumulate in the microscopic pores. Gradually, the iron oxides react with carbon and form stable complexes which deepen the black patina. This relatively low temperature process, with the rough, non-reflective surface formed by remains on the surface, creates an unevenly distributed, matte color.
Meanwhile, the furnace shrinks unevenly during its own initial firing, as the grit shrinks less than the mud. This is because the mineral particles in grits like quartz or feldspar have a higher resistance to thermal interaction. By contrast, particles in mud are more average distributed with a lower stability. This contrast generates a tensile stress that causes the matrix to rupture. These cracks are amplified by thermal expansion during the process of cooling.
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