Raku The raku firing. Equipment necessary for Raku firing. The temperature is rising, the interior of the furnace acquires the right colorus. In a moment… This is how the furnace looks from the inside. The product removed from the furnace is covered with shavings. The next stage of Raku flows in a reductive atmosphere. Ceramics will acquire a characteristic black colour. Finally, cooling down. You can enjoy the uniquely beautiful ceramics.