I own sometsuke porcelain choko Soba from Imari in the traditional five piece configuration.
Observing the soba choko one by one for a kintsugi repair, wiping off the dirt and dust that had adhered to the surface, I noticed that one cup was surprisingly cracked compared to the whole.
I immediately thought that this one was poorly repaired with a mixture of commercial glue, so I decided to separate the glued elements for a future kintsugi urushi.
I use the acetone compression technique for a few hours on the cracks to dilute the glue and despite the compresses, no result... A little disappointed, I observe more carefully. To the touch, the transparent parts (whitish) are very hard.
I ask a Japanese friend who knows the history of ceramics in Japan and I send him a picture of the soba cup. I quickly got an answer and explained that the cup was repaired with an ancient Japanese technique called "YAKITSUGI", a repair by firing technique.
YAKITSUGI’S STORY
In the main cities of Japan such as Kyoto, Osaka and Edo (former name of Tokyo),
there are many leftovers of chawan plates or bowls dating from the 19th century, whose pieces are glued together by a kind of glue.
This is a repair method called yakitsugi, which appeared during the second half of the Edo period.
Several excavations in the city of Kyoto have revealed a large quantity of leftovers gathered in holes or wells located in basements.
In the sixth volume of the illustrated encyclopedia of the 19th century by Morisada Kitagawa, it is written about the yakitsugi:
« In the past, every broken pot was repaired with urushi kintsugi lacquer.
For the first time in the Kansei* era, shiratama powder was used for yakitsugi repairs. »
« Luxury pottery or tea utensils that can't stand a second firing. »
« Yakisetu (gluing by firing) is preferred for everyday pottery. »
In the book Morisada KITAGAWA (Morisada Manko), it is stated that the main material is shiratama powder.
This one being crystal powder used for glazing and enameling. Still called shiratama powder today.
Shiratama is a compound of several elements: minium (red lead oxide), ceruse (white lead or basic lead carbonate),
silica stone, boric acid and borax.
The process of making shiratama is:
- The firing in a crucible at 1200 degrees of the powder assembly (dry powder of the different elements);
- The rapid cooling by water of the paste resulting from the melting of this powder assembly.
The resulting agglomerated white mass is called shiratama (shira: white; tama: ball).
This white mass is then crushed to obtain a very thin powder.
Yakitsugi is the principle by which the glaze is welded to the pottery material.
To glue the elements together, first mix the shiratama powder with nikawa glue (a kind of translucent gelatin), then knead the whole while adding water; then apply the paste obtained on one side with a herabo (small stick).
At this stage, the glue is already working, and the broken pieces are glued temporarily.
The final welding step is performed by placing the object in a small oven heated between 500 and 700 degrees.
However, it is important to know that only porcelain is fired, and that pottery is not subject to the same procedure. Because porcelain is fired at a high temperature of about 1250 degrees, it is very he
at resistant and does not break easily even when double fired in an oven.
The appearance of yakitsugi, was made in the tragic context of the famine of the Tenmei era** which caused great damage at the national level.
Moreover, in the 8th year of Tenmei era (1788), a big fire ravaged 80% of Kyoto city, which destabilized not only the ordinary people, but also the court nobles and samurai families.
Thus, it is considered that yakitsugi has emerged as an anti-waste means, inspired by the techniques of decoration on Kyoto glaze (uwaezuke).
Yakitsugi art of Chinese repair Ere Kansei *: de 1789 to 1801
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