“Blue and white pottery” are called “Sometsuke” in Japanese. Pottery and porcelain are decorated under the glaze with a blue pigment, generally cobalt oxide.
The following gallery shows my recent “Sometuke” works.
What is the “Gosu”
The cobalt pigment is one if of the very few that can withstand the highest firing temperatures that are required. Historically, many other colors required over glaze decoration and then a second firing at a lower temperature to fix it. This painting method is called “Uwaetsuke” (Over glaze painting)
The origin of this decorative style was imported from China. White Chinese stoneware with their own glazed, white pottery and added decorative motifs in blue glazes.
Blue and white decoration first became widely used in Chinese porcelain the 14th century.
Blue and white ware making is appearance in Japan. Where it was known as sometsuke. Various forms and decorations were highly influenced by China, but later developed its own forms and styles.
Gosu and how to use of it
A variety of the “Gosu” are available from pottery supplier. Blue, Black and also various colors of the gosu is available. Some of them are come as powder or paste.
In kyoto (Kiyomizu Yaki), a gosu is crushed by the grinding ball mill for a month.
How to use the gosu: Use the gosu with tapped water or green tea. Some pro pottery painter prefer using green tea over the water. If green tea is used, make sure that all tea waste are removed.
Green tea contains “tannin” component. This main green tea component will combine with cobalt oxide and become tannin oxide. The tannin oxide will work as adhesive.
How to mix own “Gosu” -Formulation example
Here’s formulation example:
- Cobalt oxide 20
- Nickel oxide 10
- Manganese dioxide 10
- Kaolin 50
Please use as reference only and be careful to make at your own risk. The final results are not guaranteed.
How to practice “Sometuke” YouTube
How to improve your “Sometsuke” techniques
- Use quality paint brush, need high quality fine point brush for line drawing (Known as “Kotsugaki”) and “Dami ” brush–a fat brush to paint wide area.
- Grind gosu well with a mortar and pestle
- Decorate a lot of works–More you do, become better