Reported practice · r/Kintsugi

Sanding and polishing maru-fun in kintsugi: cure, abrade, suri-urushi, repeat

How should a practitioner sand and polish a line of round gold powder (maru-fun) applied in a kintsugi repair so that the metallic shine is maximised without losing the powder, and what intermediate steps are required between the initial application and the final surface?

This page is written from one discussion thread. It records what practitioners reported and what they linked it to — not documented workshop practice. Every claim below links to the comment it rests on, so you can read it in context.

Safety

The work described involves repeated handling of raw and refined urushi (kijomi-urushi, suri-urushi). Urushi is a potent skin sensitiser; contact can produce a delayed urushiol dermatitis that may appear 24–72 hours after exposure and can become progressively more severe with repeated contact. Gloves, long sleeves, and avoidance of skin contact are essential throughout every step.

What the thread establishes

The answer.

The thread establishes a sequence: first apply consolidation coats (fun-gatame) of kijomi-urushi over the powder to lock the granules into the lacquer matrix, then allow those coats to cure fully (the practitioner used five days at 80 % humidity). Once hardened, abrade the surface flat with a fine abrasive—either maki-e-grade charcoal or a synthetic stone such as a #3000 crystal toishi—using a very light touch so the gold is levelled rather than removed. After the surface is flat and a metallic sheen appears, apply a coat of suri-urushi (kijomi-urushi wiped on and back off) to fill residual cavities between granules, then polish. The practitioner notes that two further suri-urushi-and-polish cycles are needed to complete the finish. The surface will never read as a perfectly uniform sheet at close range; the individual round granules remain visible, and the aim is to minimise the gaps between them rather than to eliminate them.

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What goes wrongTwo failure modes are identified. If the fun-gatame consolidation coats have not fully hardened before sanding begins, the powder granules tear out of the lacquer instead of being abraded flat, leaving a pitted, non-reflective surface. Conversely, if the abrasive is pressed too hard during the sanding step, the gold is cut through entirely, exposing the substrate beneath and destroying the decorative line.

What recovers itThe thread does not describe a recovery for granules that have already been torn out or for gold that has been sanded through. The emphasis throughout is on prevention: thorough curing before abrasion and a consistently light hand during sanding. The suri-urushi step after sanding serves to infill small cavities and roughness that remain between granules, improving the eventual shine, but it is presented as a normal part of the sequence rather than a corrective measure.

Apply fun-gatame consolidation coats

Apply one or more thin coats of kijomi-urushi over the maru-fun line to embed the granule-like gold particles within the lacquer. These consolidation layers (fun-gatame) are essential before any abrasion is attempted.

the comment this came from ↗

Cure the consolidation coats thoroughly

Allow the fun-gatame coats to harden completely before sanding. The practitioner used a period of five days at 80 % relative humidity. If the coats are not fully set, the granules will tear out rather than abrade flat.

the comment this came from ↗

Sand the line flat with a fine abrasive

Using maki-e-grade charcoal or a synthetic abrasive block (the practitioner used a #3000 crystal toishi), abrade the surface with a very light hand until the powder and lacquer are level and a metallic sheen appears. The goal is to flatten, not to remove the gold.

the comment this came from ↗

Apply suri-urushi and polish

Wipe on a coat of suri-urushi (kijomi-urushi applied and then wiped back off) to infill cavities and roughness between granules. Once cured, polish the surface. Repeat the suri-urushi-and-polish cycle; the practitioner required two additional cycles to complete the finish.

the comment this came from ↗

··Reported

What was reported

Fun-gatame consolidation coats of kijomi-urushi are required over maru-fun to lock the granular gold particles into the lacquer before any sanding can be done. ↗
If the consolidation coats are not fully cured, the powder granules tear out during sanding instead of being abraded flat. ↗
The practitioner cured the fun-gatame for five days at 80 % humidity before beginning the sanding sequence. ↗
Sanding can be performed with maki-e-grade charcoal or with a synthetic abrasive block; the practitioner used a #3000 crystal toishi. ↗
A very light hand is essential during sanding to avoid abrading through the gold entirely. ↗
Suri-urushi (kijomi-urushi wiped on and off) is applied after sanding to infill cavities and roughness between granules, improving the eventual polish. ↗
A maru-fun surface will not read as perfectly homogenous at close range; individual round granules remain visible, and the objective is to minimise the gaps between them to maximise shine. ↗
The practitioner required two additional suri-urushi-and-polish cycles after the initial sanding-and-polish pass to complete the finish. ↗
Close-up reference images of a well-finished maru-fun surface are difficult for self-taught practitioners to find. ↗
The kintsugi work described is functionally a use case of maki-e technique, and basic maki-e instruction is available in video form on YouTube and other platforms. ↗

Limits of this source

What the thread does not answer.

No video demonstration of the close-up sanding and polishing of maru-fun is available from the practitioner, and the thread acknowledges that finding clear close-up reference images of a well-finished maru-fun surface is difficult for self-taught workers.
The thread does not specify the exact grit progression if multiple sanding stages are used, nor the specific polishing compound or tool (beyond 'polishing') for the final suri-urushi-and-polish cycles.
The relationship between the number of fun-gatame coats and the number of suri-urushi/polish cycles is not quantified; the practitioner gives one instance (one fun-gatame coat, then two further suri-urushi/polish cycles) without stating whether this ratio is fixed or variable.

Read the documented methods →