Lacquer base

A lacquer base coat is used before applying the lacquer to reinforce any imperfections and smooth the surface; it's like cement in architecture. Rust and other imperfections are also part of this, but this time we'll be focusing on "ground powder."

"Ji no kō" refers to a mixture used as a base coat for lacquer in various lacquer-producing regions. It is made by mixing a mixture of water and glue with raw lacquer, and comes in many varieties, including earth, sand, and diatomaceous earth.

The mysterious powder called "M-ji no kona" used in the kintsugi class is an imitation of Wajima-ji no kona, a type of diatomaceous earth that is steamed and baked, used in Wajima. Wajima kept the ji no kona a closely guarded secret, so only members of the Wajima Lacquerware Association can buy it.

Rust lacquer (lacquer base)

Rust lacquer is a versatile lacquer base made by mixing lacquer and polishing powder to create a smooth paste, which is mainly used to smooth out rough surfaces, fill in imperfections, sharpen corners, and fill in minor dents.

To explain what "tonoko" is, it is a product manufactured and processed in Yamashina, Kyoto. The geological layers of Yamashina are crushed and then filtered to separate them by coarseness, and the components are further divided into red, yellow, and white polishing powders for different uses. The coarser powders are called "jino-ko" (ground powder), and the finer powders are called "tonoko."

"Water filter" → This is a classic method in which particles are placed in a container of water, stirred, and then left for a while. The coarser particles settle at the bottom, while the finer particles remain on top. By separating the water into tap water and sewage, and repeating the water filter process multiple times, or by using a fine mesh filter in combination, it is possible to obtain fine and uniform particles.

It is also used to distinguish the coarseness of mineral pigments and porcelain clay used in Japanese painting.

- Rust-colored lacquer used to fill in and smooth rough lacquer bases is called "decorative rust."

- To fill in small dents, use "repair rust" or "add-on rust".

- "Roiro rust" fills in very subtle, tiny dents.

- "Rust-filling" to fill long grooves, etc.

- "Kukuri-sabi," a type of rust with a high lacquer content, often found on the rims of bowls.

- Rust that has been colored by mixing in pigments: "Colored Rust"

- For filling (sealing) the wood's pores, rust is used because it has a low lacquer content and is less prone to shrinkage.

In Wajima, they sometimes mix in a small amount of rice paste. (Examples: "Hachisabi," etc.)

* "Vessels" → When viewed under a microscope, wood has a structure that looks like bundles of long fibers, and these fibers are hollow like straws.

These are called vessels, or sometimes called the blood vessels of the tree.

Some trees have large (coarse) vascular tissue (such as zelkova), and the process of filling in these coarse vessels during construction is called "filling." Sometimes they are intentionally left unfilled, but it depends on the desired final finish.

↑The mixture will be adjusted according to the intended use, but I think even just using rust-colored lacquer won't cause too much trouble. Just for reference.