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Kanshitsu

Kanshitsu is a body made of linen cloths or Japanese paper hardened with urushi (lacquer), which allows free modeling.


This technique was introduced from China and was widely used in Japan to produce Buddhist statues from the late 7th to the 8th century.
In the case of Buddhist statues, wooden cores are often used, but in the case of urushi objects, a plaster model is made, and several layers of linen cloths are pasted onto the plaster with urushi and it's dried and harden before being removed from the plaster model to form a body, which is 2 to 3 mm thick.

Illustration of Cross Section
Partial enlargement of a cutaway drawing of kanshitsu (illustration). The order of the procedure is as follows: plaster mold, base, linen, primer, and urushi (Japanese lacquer) for painting.

Contents for this article

Work procedure

The shape of the finished vessel.

1. Draw a plan.
Details
Draw the shape from above and another one from the side.
2. Make a sweeping mold with a plastic board.
Details
The large circle shape seen from above is the round plastic plate at the bottom, and the curved line seen from the side is the sweeping mold.
Use a 1 mm thick plastic board for smaller vessels and a 2 mm thick plastic board for larger vessels.
A vertical thin rod stands in the center of the bottom and the sweeping mold are reinforced with wood to stabilize them.

3. Modeling with plaster.
Details
Place a large glass board on a rotating table.
Place clay or styrofoam inside so that the plaster is 2~3 cm thick.
Be careful not to wash out the plaster with a water tap.
If the shape cannot be modeled with a sweeping mold, plane the plaster with a plane or carving knife, and then sandpaper to smooth it.
4. Dry
Details
After drying, remove the inner clay or styrofoam.
5. Apply mold release agent to the plaster model (2 to 3 times)
Details
After boiling glutinous rice flour and water to make a paste, add a little paint to it. (To make it easier to see if the thickness is even when colored.)
Place something in the empty space inside the plaster (the beige part of the image).

6. Apply tonoko-sabi (fine-grained base paste) and jinoko-sabi (coarse-grained base paste) twice each in this order.
Details
Do not use a brush for painting, but use a brush (horsehair) to process kanshitsu. If you do not have that type of brush, use another proper brush or a spatula.
Smooth the surface with a sandpaper while keeping the uniform thickness.
Tonoko is a fine-grained stone powder, and jinoko is a stone powder with slightly larger particles than tonoko.

7. Cut a piece of fine linen cloth (#100~#110) to a size that extends 4~5 cm beyond the vessel.

8. Apply the cloth of 7.
Details
Make a glue of from glutinous rice powder + ki-urush.
Leave 1 cm of cloth over the bottom and apply it to the plaster. (After that, do not apply the protruding cloth to the plaster, but cut it off at the edge.)
After drying, cut the overlapping cloth with a carving knife.
9. Fill in the fablic
Details
Make a glue made of glutinous rice powder + ki-urushi + Wajima-ground powder and rubbed into the recesses of the fabric with a spatula, and after it dries, it is polished dry with sandpaper.

10. Apply 3~5 sheets of coarse linen cloths (#25~#80) in the same procedure as 7.~9.
Details
Do not protrude the cloth to the bottom (the edge).
Apply 1~2 more cloths only to a part where you want more thickness.
When attaching legs or the edge of the bottom backside, attach them after applying the last layer of coarse linen cloth.

11. Apply a piece of fine linen cloth (#100~#110) in the same procedure as 7.~9.

12. Apply jinoko-sabi (coarse-grained base paste) and tonoko-sabi (fine-grained base paste) twice each in this order.
13. After polishing with a whetstone, harden with ki-urushi., and after it dries and hardens, apply one coat of black urushi.

14. Remove uneven edges
Details
Cut off any excess cloth or the base layer that has appeared below the lower portion (the edge) with a carving knife.
Then scrape the lower portion on a large flat surface sandpaper until the plaster comes out.
The portion where the cloth and the base layer appeared is then coated with several coats of ki-urushi and add Tonoko-sabi (fine-grained base paste) and waterproof it well for the process in 16.
15. Dry (harden)
Details
If necessary, place it in an oven at a temperature of 80°C for 24 hours to harden well.
If the inside is not firmly hardened, the shape of the vessel may be distorted after it is removed from the plaster model. If an oven is not available, to reduce this risk, ensure that each step in the process hardens one fully at a time.
For more detailed material on the baking of urushi, please refer to "Study of Traditional Baking urushi Techniques". [1] (National Research Institute for Cultural Properties, Tokyo) though it's in Japanese. However, this is not a discussion of kanshitsu but applying urushi on a metal base.

16. Soak in water for several hours and then remove the plaster model.
Details
In the case of trays and plates, the plaster model can be reused because it will come off simply by applying force due to the mold release agent. For boxes, the plaster model would be broken using a chisel, hammer, or carving knife.

17. Grind the inside of the vessel with a whetstone to a smooth surface, possibly filling it with tonoko-sabi (fine-grained base paste).
18. If the rim is to be thinned, shave it with sandpaper to adjust the thickness. If the layer of cloth is exposed, apply tonoko-sabi (fine-grained base paste) to smooth the surface and grind with a whetstone.
19. Proceed with the overall painting process to finish.
POINT

If the base layer is made thicker, the vessel becomes heavier and more prone to chipping, so proceed with each step, keeping in mind to make the uniform thickness and thin as possible. It means that the minimum thickness is required so that the weave of the cloth will not show up weeks after completion.


Description

Advantages of kanshitsu
It can be freely formed into any shape.
It does not deform like wood.
It is more durable and sustainable.

Hemp cloth does not allow the urushi to penetrate to the core of the threads, leaving the fibers of the hemp cloth, which makes a kanshistu body more robust. It rarely cracks when dropped, only chipping outside of the sabi (base layer made of urushi and sand).

Disadvantages of kanshitsu
It taks more time and is labor intensive.
It costs more because a lot of urushi is used.
It is often heavier than a wooden body.

It is a technique that allows for free ideas to be transformed into modeling, but the treatment of details varies from shape to shape, and there are many occasions when new innovations are required. For trays and boxes, For trays and boxes, legs or an edge on the bottom backside made of wood would be necessary.

The body is made to be uniformly thick, so more cloth is applied or a wooden core is inserted in the part that needs to be thicker. In addition, the lid and body of the box must fit together properly, which requires a high level of skill.
For example, in the case of a box, there are several points as shown below.

Make the part that receives the lid (light blue part) and the edge on the bottom backside (pink part) with wood and attach them to the body.

1. Thin the edge and round it.
2. Calculate the gap with the lid to be about 1 mm after completion.
3. Apply more cloth and make it a little thicker.
4. Make the part that receives the lid with wood and attach it.
5. After attaching the edge on the bottom backside with wood, plane and make the outside smooth along with the part of 4.


Plaster work

A plaster model for kanshitsu is needed

First, a plaster model is needed.

Dry the plaster model for kanshitsu.

Dry them for 1-2 days.

It's a model for kanshitsu. After drying them, smooth the surface with a plane or sandpaper.

After drying them, smooth the surface with a plane or sandpaper.

Samples of the production process of kanshitsu by Living National Treasure, Mr. Mashiki Masumura can be viewed at Cultural Heritage Online.


References

1. Toshio Kinoshita, Hiroshi Ueno, Toshikatsu Nakazato, Seiko Miyata. (1998). "Study on Traditional Burnt urushi Technique". National Research Institute for Cultural Properties, Tokyo(PDF file)
2. Japan Crafts Association. "Works of Mr. Kiichiro Masumura (Living National Treasure)”. Japan Kōgei(art crafts) Association
All of them are in Japanese.

My works of kanshitsu



2024.05.14
2025.04.30