Generally speaking, pine firewood has been widely used since ancient times because it is suitable for firing ceramics due to its long life, low ash content, and lack of metal sulfide. Soft woods with high resin content, such as red pine, are the best. This is because soft wood has a high calorific value. Hard wood keeps the fire well, but the flame is short.
For kilns that place great importance on the flame, such as painting kilns, red pines that are not too old, straight, and without knots should be used. For firing in the base, the selection of wood is somewhat easier. Some people prefer pinewood for glaze colors, as they believe that only pinewood can produce good colors. For example, it is said that coal cannot be used to produce the expected colors of gosu-zome and lapis lazuli. However, as a result of over-cutting, good wood became scarce and expensive, and from the Taisho and Showa decades, coal and other fuels were adopted.
