Gosu is a traditional underglaze pigment used for sometsuke (blue-and-white decoration) on ceramics. It is primarily made from cobalt oxide, blended with small amounts of metals such as iron and manganese to produce rich, deep blue tones.
 
 This product is supplied as a powder and should be mixed with water before use. For enhanced color development, it can also be mixed with green tea, a traditional technique used by many potters.
 
 Simple instructions for use are included.