Can you preserve fire? Yes! And you can see it right here on the surface of this raku vase. In a raku firing, you can often see the pattern of the flames in the glaze, even more so on the back of this vase than on the front.
Raku is an ancient technique of firing clay, the roots of which go back to 16th century Japan. Unlike other glaze firings where the kiln is slowly brought up to temperature and then allowed to cool slowly, raku is fired very quickly--from room temperature to 1750 and back to room temperature in about an hour. When the kiln has reached the correct temperature, it is opened, the pieces are removed using long tongs, placed in a pit lined with sawdust, and quickly covered with a metal pot or container that is lined with straw. The combustibles use up the oxygen in the container, producing beautiful metallic colors. The unglazed areas of the pot absorb carbon from the burning organic matter and become black. This process DOES NOT create a waterproof vessel. It is decorative only. However, I have often put the stems of flowers into a ziplock bag, added water, stuffed the bag into the vase so it is not visible, and zipped it closed as far as possible.
This piece is about 13" tall.