On Tuesday, March 17, the 7th and 8th grade science students had
the opportunity to fire pottery in a raku kiln with the
assistance of Mr. and Mrs. Laury, OLS parents who also teach art at Chaminade.
In preparation for the lesson, the students made cylinders out of raku clay. The cylinders were fired in the electric kiln in the art room by
Mrs. McGrath. The students then applied a copper glaze to the cylinders, which made them ready for the final firing.
Why is this science?
The
raku kiln is heated to 1800 degrees F. The pottery is then placed in
the kiln for about 15 minutes. Once they are glowing, the pieces are ready to be
taken out of the kiln. The appearance of the glazed part of the
pottery is green as one would see on an old penny. After the kiln, the cylinder was
immediately placed in a bucket with shreded newspaper. The hot pottery caused
the paper to catch on fire, and Mr. and Mrs. Laury immediately put a lid on the bucket to extinguish it. However, the fire looked for oxygen to continue burning and
took it from both the clay and the glaze causing them to change in
appearance: the clay turned black and the glaze became shiny. The
cylinders were carefully removed from the buckets and placed in very
cold water causing an immediate thermal reduction, making the glaze
shine. After cooling, the cylinders were cleaned and polished.
This video shows a snippet of the process as the cylinders are moved from the newspaper-filled bucket into the cold water bath:
Special thanks to Mr. and Mrs. Laury for their time and expertise and for making this lesson possible!