Necessary Tools and Materials for Kintsugi

There are various traditions about the materials used for kintsugi.

As a result, teaching methods vary widely from person to person.

This often confuses beginners.

This article lists the most commonly used materials and summarizes their uses.

However, the case of traditional kintsugi is assumed here.

Please note that what is needed for alternative kintsugi is very different.

 

Materials required for Kintsugi

If you want to do kintsugi, you will need these tools and materials.

 

Necessary materials

• Raw urushi
• Wheat flour
• Tonoko-powder
• Kokuso-powder
• Bengara urushi
• Gold powder
• Cotton ball
• Ethanol
• Vegetable oils

 

Necessary tools

• Water-resistant gloves
• Acrylic plate
• Spatula
• Brush
• Masking tape
• Art knife
• Diamond file
• Water-resistant sandpaper
• Tissues paper
• Small box to store repair items
• Towels

 

As I will explain later, some of them can be substituted with other materials.

Also, since this is really only a minimum list, if you want to do a higher quality repair, you will need to use more materials.

 

 Next, let's look at how to use each of these tools and materials.

 

Raw urushi

This is the most important material in kintsugi.

It is the sap extracted from the lacquer tree.

When it comes into contact with moisture in the air, it undergoes a curing reaction and becomes a robust natural resin.

 

Purpose

• Ingredient for mugi-urushi (used for gluing)
• Ingredient for sabi-urushi (used to fill grooves in joints)
• Ingredient for kokuso-urushi (used to fill in chips)
• Filling cracks

Because of its excellent adhesive strength and fastness when resinified, it is often used as a base material for repair such mugi-urushi and sabi-urushi.

 

 Substitutes

•  None (epoxy resin, if anything)

Urushi is a substance with very specific properties, so basically it cannot be substituted with other materials.

Although it is not a direct substitute for raw urushi, epoxy resin can be used in place of mugi-urushi or sari-urushi made from raw urushi.

However, this area is in the realm of alternative kintsugi, so I will not discuss it here.

 

 

Wheat flour

There are various types of wheat flour, but you can make repairs with cake flour, all-purpose, or bread flour.

 

Purpose

• Ingredients for mugi-urushi (used for gluing)

Cake flour is used only when it is mixed with raw urushi to make mugi-urushi in the gluing process.

It is not impossible to glue raw urushi by itself, but mixing it with wheat flour makes it stickier and easier to work with.

There are various other merits and demerits, but I will write about them in another blog.

 

Substitutes

• Rice flour

In addition to "Mugi-urushi", there is also a technique using "Nori-urushi" in the gluing process of kintsugi.

Wheat flour is used for mugi-urushi, while rice flour is used for nori-urushi.

I have not experimented with it myself, but from what I have seen and heard, I think mugi-urushi is a better adhesive.

 

 

Tonoko

Simply put, it is rock made into a very fine powder.

In kintsugi, the term "Tonoko" often refers to the powder produced in Yamashina, Kyoto.

 

Purpose

• Ingredient for sabi-urushi (used for filling in grooves in joints)

• Ingredient for kokuso urushi (used to fill in chips)

Due to its nature, raw urushi does not harden well when applied thickly, and cannot be used as it is to fill in the joints

On the other hand, when raw urushi is mixed with tOnojo, it hardens firmly even when applied somewhat thickly, so it can be used to fill the grooves in the joints.

 

Substitutes

• Rusty soil

There are two main reasons why tonoko is used for "sabi-urushi.

One is that its fine texture blends well with raw urushi, and the other is that its main ingredient is silica, which remains highly durable even after hardening.

Conversely, if these conditions are met, other soils are generally acceptable.

Specifically, Kiso rust soil, which contains high iron content, is a well-known example.

 

 

Kokuso-powder

This is powdered cotton or hemp fibers.

Adding a small amount to the base paste of sabi urushi, etc., increases its strength and allows it to harden firmly even when applied thickly.

 

Purpose

• Ingredients for kokuso-urushi (used to fill in chips)

 There are many ways to make kokuso-urushi.

Basically, "raw urushi" is added to "tonoko" or "wheat flour" to make a paste, to which some kind of fiber such as "kokuso-powder” is added, which is called "Kokuso-urushi".

Since it hardens even when applied somewhat thickly, it is used to fill in chips.

 

Substitutes

• Wood powder

In addition to cotton and hemp, "wood powder" is often used as one of the fibrous materials for making "kokuso-urushi".

For example, there are techniques mixing "Mugi-urushi" with "wood powder" or adding "wood powder" to "Nori-urushi". 

However, I personally do not recommend the method of mixing "wood powder" because it tends to peel off over time. 

 

 

Bengara urushi

Benagara urushi is made by refining raw urushi to reduce its water content, adding red pigment, and kneading.

 

Purpose

• First coating
• Second coating
• Finish Coating

It is used in the first and second coating processes to fill in the minor grooves of joints.

Bengara urushi is also used before aplying gold powder as a finishing touch.

 

Substitutes

• Black urushi (only for the first and second coating)

The main purpose of the first and second coating is to fill in the minor grooves.

Therefore, other urushi with low water content, such as black urushi, can be substituted.

Very roughly speaking, black urushi and bengara urushi are only different in color.

Rather, working with black urushi for the first and second coating makes it easier to see the remaining coats when applying the bengara urushi in the finish coat.

If possible, it is better to use black urushi.

 

However, bengara urushi is more suitable for the finish coating.

This is because a red base coat improves the coloring of the gold powder on top of the base coat.

Therefore, it is not recommended to use black urushi for the finish coating.

 

 

Gold powder

 It is used in the last step to decorate the joints with gold.

 Basically, gold powder used in kintsugi is pure gold.

 However, a small amount of silver or copper may be mixed in to adjust the color.

 

Purpose

• Decoration of joints

Bengara urushi is applied to the joints and gold powder is aplied on top of it to make the joints gold-colored.

 

Substitutes

• Brass powder, etc.

Since gold powder is used only as a final decoration, brass powder and other similarly colored powders can be used as substitutes.

However, be careful to use fine particles or they will have a rough appearance and texture.

Also, unlike pure gold, brass will dull in color over time.

In addition to brass powder, you can also use mica powder.

 

 

Silk ball

Silk fibers in a soft, rounded state.

 

Purpose

•  Decoration of seams

This is necessary in the process of adhering gold powder to the joints.

Use rounded silk with gold powder and gently place it on the joints.

 

Substitutes

• None

 There are not many substitutions for silk ball.

 

 

Ethanol

Ethanol is a type of alcohol.

For example, ethanol is contained in alcohol disinfectant, and alcohol in common alcoholic beverages is also ethanol.

It also has an aspect as an organic solvent, and this aspect is used in kintsugi.

 

Purpose

• Wiping off urushi

Urushi cannot be sufficiently washed away with water or soap.

Therefore, ethanol is used to clean tools with urushi.

The higher the concentration, the stronger the cleaning power.

If possible, I recommend using anhydrous ethanol, which is close to 100% pure ethanol.

 

Substitutes

• Methanol
• Acetone
• IPA (Isopropyl alcohol)
• Turpentine oil
• Camphor oil

There are many substitutes when it comes to cleaning urushi, but they are all basically organic solvents. 

Personally, I believe the important thing here is to be fully aware of the dangers of each.

In particular, "methanol" is similar to "ethanol" in name, but has a very different degree of danger, so please check carefully before purchasing.

 

If there is no particular reason, it is better to use ethanol, which is relatively safe.

 

 

Vegetable oil

Salad oil, rapeseed oil, or any other common vegetable oil found in the home is acceptable.

 

Purpose

• Cleaning brushes used to apply urushi

Most tools are cleaned only with ethanol as described above, but only brushes used to apply urushi are cleaned with vegetable oil.

Using vegetable oil prevents the brush tips from hardening during storage.

 

Substitutes

• None

 

 

Water-resistant gloves

Urushi can cause a severe rash if it gets on the skin, so be sure to wear gloves while working. 

Nitrile gloves are recommended because they are thin and easy to work with, but rubber gloves are also acceptable.

If you have sensitive skin or are concerned about stains on your clothes, arm covers are also a good idea.

 

 

Acrylic plate

In addition to an acrylic board, a flat, water-repellent material such as a glass plate or enamel would be easy to use.

A size of about 10 cm x 10 cm is also sufficient.

 

 

Spatula

It is used to handle pastes such as mugi-urushi and sabi-urushi.

If possible, it is convenient to prepare two types, one slightly larger and one slightly thinner, so that you can use one for kneading and the other for applying.

 

 

Brush

Traditionally, a maki-e brush made of mouse hair is used, but beginners can work with a commercially available nylon brush.

A brush with a thin tip and not too long will be easier to use.

If possible, a small flat brush should also be prepared to make it easier to apply to slightly larger areas.

 

 

Masking tape

It is used to protect the bare surface of repaired items from urushi stains and to secure debris during adhesion.

3M's 243J series is easy to use with good water resistance and adhesive strength.

Masking tapes found in grocery stores are often weak in these points.

 

 

Art knife

It is used to shave mugi-urushi and sabi-urushi after hardening.

Since it is difficult to scrape curved surfaces with a straight blade, it is recommended to use a design knife with a curved blade attached.

 

 

Diamond file

Used for chamfering pieces before gluing.

Most commercially available products are too rough and are not suitable for chamfering.

It is advisable to choose a grit of #400 or higher.

The shape should be semi-round.

 

 

Water-resistant sandpaper

It is used to scrape off sabi-urushi and kokuso-urushi after it has hardened.

A grit of about #800 is sufficient.

Since sabi-urushi and kokuso-urushi become soft and easy to scrape when moistened, a water-resistant sandpaper that can be sharpened with water is recommended.

 

 

Tissues paper

It is mainly used to clean urushi with ethanol.

Any commercially available product, such as Kleenex, can be used.

 

 

Small box to store repair items

Prepare a box to store repair items while humidifying them after work.

The smaller the volume of the box, the easier it will be to maintain high humidity levels.

If the repaired item itself is large, choose a container that is as close in size to the repaired item as possible.

The amount of oxygen inside the container is also important, so cardboard or similar material that is somewhat breathable is recommended over a container that is completely sealed.

 

 

Towels

To keep the humidity in the box high, place a wet towel inside the box.

If the box is large, using a vaporizing humidifier that does not require electricity can also be effective.