The Traditional Gold Repair Process

There is a particular kind of patience required to repair something the right way. Not the patience of waiting for glue to dry — that is just clock-watching. The patience of kintsugi is something altogether different: a willingness to stay with a broken object for weeks, sometimes months, coaxing it back to wholeness with materials that have been used in Japan for over ten thousand years.

Most people who encounter kintsugi for the first time assume it must be relatively quick. Gold is applied to the crack, and the bowl looks beautiful again. The reality is considerably more involved — and considerably more interesting.

Table of Contents

1.  True Kintsugi vs Modern Kintsugi

2.  First, a Word About Materials

3.  The Steps, In Order

3-1  Assessment and Cleaning

3-2  First Adhesive Layer — Mugi-urushi (麦漆)

3-3  Filling Deep Chips — Kokuso (刻苧)

3-4  Smoothing with Sabi-urushi (錆漆)

3-5  Intermediate Lacquer Coats — Nuri-urushi

3-6  The Gold — Maki-e (蒔絵)

4.  How Long Does It All Take?

5.  Frequently Asked Questions

1. True Kintsugi vs Modern Kintsugi

Before going further, it is worth clarifying something that causes considerable confusion in the market.

The word 'kintsugi' now appears on a wide range of products — craft kits, repair sets, and online tutorials — many of which use synthetic adhesives, epoxy resins, or chemical lacquers mixed with gold-coloured mica powder. These produce something that looks superficially similar to the real thing and can be completed in an afternoon. They are often called 'modern kintsugi.'

Honkintsugi (本金継ぎ) — literally 'true gold joinery' — is different in every respect. It uses urushi (漆), the sap of the Japanese lacquer tree, as its adhesive and coating medium; genuine gold, silver, or platinum powder as its finishing material; and a multi-stage process that takes months rather than hours. The result is food-safe, extraordinarily durable, and grows stronger over time — properties that synthetic resins cannot replicate.

The process described in this article is honkintsugi. When we refer to 'kintsugi' at atelier_muho, this is always what we mean.

2. First, a Word About Materials

The foundation of traditional kintsugi is urushi (漆) — the sap of Toxicodendron vernicifluum, the Japanese lacquer tree. Urushi has been harvested and used in Japan since the Jōmon period (approximately 10,000 years ago), and its properties remain unmatched by anything synthetic: once fully cured, it is resistant to acid, alkali, heat, and water. Unlike epoxy resins, which yellow and weaken within years, urushi grows harder and more lustrous with age. It is often said that urushi does not reach its true hardest state until it is well over a century old.

One important note for anyone handling raw urushi: the uncured sap contains urushiol, the same compound responsible for poison ivy reactions, and can cause skin irritation on contact. Rubber gloves are essential throughout the process.

Key Materials at a Glance

•       Mugi-urushi (麦漆) — raw urushi + wheat starch flour. Primary adhesive.

•       Kokuso (刻苧) — urushi + wood powder + wheat starch. Fills deep chips and missing sections.

•       Sabi-urushi (錆漆) — urushi + tonoko (砥の粉, powdered whetstone). Fills and levels the surface.

•       Roiro-urushi (呂色漆) — refined, filtered lacquer for decorative coats.

•       Bengara (弁柄) — iron oxide red pigment mixed with urushi. Base layer for gold application.

•       Maki-e powder (蒔絵粉) — fine gold, silver, or platinum powder applied at the final stage.

What you will not find in a honkintsugi repair is epoxy resin, turpentine, or any modern chemical substitute. Turpentine, while used by some contemporary practitioners, is not part of the historical tradition — it entered Japanese craft only in the 20th century through Western painting influence — and is not necessary for a successful repair.

3. The Steps, In Order

Step 1: Assessment and Cleaning

Before anything else, the broken pieces are carefully assessed. How many fragments are there? Do they all align cleanly, or have small chips been lost along the break? A skilled practitioner will spend real time simply looking — understanding the nature of the break before attempting anything.

The fragments are then cleaned thoroughly to remove any previous adhesive, dirt, or grease. Even a thin film of oil on a shard can prevent urushi from bonding properly. If a previous repair has been attempted with superglue or epoxy, that residue must be fully removed before honkintsugi can proceed.

Step 2: First Adhesive Layer — Mugi-urushi (麦漆)

The first stage of joining uses mugi-urushi — raw urushi and wheat starch flour worked together into a paste. This is applied to the broken edges, the pieces pressed together, then secured with masking tape to ensure nothing shifts while the lacquer cures.

This step is more critical than it might appear: if pieces are left even slightly misaligned, the error compounds through every subsequent layer. Once mugi-urushi hardens, realignment becomes extremely difficult.

The joined piece is placed in a muro (室), a humidity-controlled curing box. Urushi cures through an enzymatic reaction that requires both moisture and warmth. Optimal conditions: 20–30°C at 70–85% relative humidity. At these conditions, mugi-urushi will cure in approximately 24 hours.

Step 3: Filling Deep Chips — Kokuso (刻苧)

Where sections of ceramic are missing entirely, kokuso is used to rebuild the form. This thick paste is applied with a bamboo spatula and shaped to approximate the missing area.

A critical rule: no more than 0.5–1mm per application. Kokuso applied too thickly will not cure properly, and can remain soft for weeks or even months. Each layer must be left in the muro to cure fully before the next is added.

Step 4: Smoothing with Sabi-urushi (錆漆)

Once the basic form is restored, the surface is refined using sabi-urushi — a mixture of urushi and tonoko that dries to a hard, sandable consistency. Sabi-urushi is applied in multiple thin layers, each cured and then sanded — progressing from dry sandpaper to 1000-grit waterproof sandpaper — until the repaired surface is completely flush with the surrounding ceramic.

The quality of the final gold line depends almost entirely on how well this stage is executed. If the surface remains uneven after sanding, apply another layer and sand again. This is the process, not a failure.

Step 5: Intermediate Lacquer Coats — Nuri-urushi

With the surface level, several coats of refined roiro-urushi (呂色漆) are applied to create a smooth, consistent base. Each coat is cured in the muro, then sanded with 1000-grit waterproof sandpaper. Typically three to five coats are applied.

Some practitioners choose to leave the repair at this stage for a subdued, understated result. For honkintsugi in the full sense, however, there is one final stage.

Step 6: The Gold — Maki-e (蒔絵)

First, a very thin layer of bengara-urushi (弁柄漆) — urushi mixed with iron oxide red pigment — is applied over the lacquered seam. This red base serves two purposes:

•       Gold powder adheres more brilliantly to red than to black.

•       The colour contrast makes it immediately visible if any area has been missed.

When finishing with silver powder, the sequence is reversed: black urushi goes on last, as silver reads better against a dark base. The bengara layer must be applied as thinly as possible — if too thick, gold powder sinks into it and the surface appears reddish.

Fine maki-e gold powder is then applied using a silk ball (絹ボール), working gently along the seam. The powder is polished lightly to bring up its full lustre.

Gold Powder Grades

The piece returns to the muro for a final cure, then is rinsed gently with water to remove any loose powder, and the repair is complete.

4. How Long Does It All Take?

A single repair, done in the full honkintsugi tradition, typically takes six weeks to three months from start to finish. Complex pieces — many fragments, significant material loss, very fine ceramics — can take considerably longer.

This timeline is not inefficiency. It is the nature of the materials. Each layer must cure fully before the next is applied, and the curing process cannot be rushed without compromising the result. This slow curing is precisely what makes the finished repair so durable. Urushi that has been allowed to cure slowly and completely, layer by layer, grows stronger over decades and centuries in a way that fast-setting adhesives never can.

5. Frequently Asked Questions

Q: What is the difference between honkintsugi and modern kintsugi?

Honkintsugi uses genuine urushi lacquer and real metal powder, following the traditional multi-stage process developed in Japan over five centuries. Modern kintsugi uses synthetic resins — typically epoxy or chemical lacquers mixed with gold-coloured mica — and can be completed quickly. Modern kintsugi is not food-safe, tends to yellow over time, and lacks the durability of traditional urushi. All work at atelier_muho uses honkintsugi.

Q: Is kintsugi food-safe?

Fully cured urushi is food-safe and has been used on tableware in Japan for thousands of years. The curing process is the key: raw urushi can cause skin irritation, but once properly hardened it is entirely inert. Synthetic 'kintsugi' products using epoxy or chemical resins are generally not considered food-safe.

Q: Can I repair any ceramic with kintsugi?

Honkintsugi works best on unglazed and lightly glazed ceramics. Highly glazed surfaces require light surface preparation to help the urushi bond. Very fine porcelain, bone china, and glass can also be repaired, but require additional care and specific urushi formulations.

Q: Why does kintsugi cost so much?

Because a single repair takes months of skilled work, multiple sessions, expensive natural materials, and constant attention to conditions. The cost reflects not just materials but the accumulated time of a craftsperson who has dedicated themselves to mastering a demanding traditional discipline.

Every piece in the atelier_muho collection has been repaired using traditional urushi and genuine gold powder, following the full honkintsugi process.

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