漆Urushi Archive

Reported practice · r/Kintsugi

Repairing a partial crack in a ceramic bowl without completing the break

A large (30–40 cm) heirloom ceramic bowl has a crack running up one side that does not go all the way through. The practitioner asks whether the traditional kintsugi approach requires splitting the crack fully into two pieces, or whether the urushi can be worked into the existing fissure as-is.

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

Raw urushi (ki-urushi) is a potent skin sensitiser; contact can trigger a delayed urushiol-type dermatitis. Gloves and careful handling are essential, and the reaction may not appear until hours or days after exposure.

Test the glaze and any non-ceramic surfaces for staining before applying urushi, as the lacquer can permanently discolor certain finishes.

What the thread establishes

The answer.

For a crack of this character—thick-walled, not running the full height—several commenters agree it can be repaired without completing the break. The working procedure involves cleaning the crack, wicking in a highly fluid urushi (ganshin-urushi) so it penetrates the fissure, curing in a humidity chamber, then proceeding through the standard kintsugi sequence of sabi, nakanuri, and gold application. A companion piece in the same set has a missing fragment, for which a hemp-gauze internal structure built up with kokuso and sabi is suggested. Multiple commenters stress that a first-time practitioner should practice on inexpensive ceramics before touching an heirloom, and that the glaze must be tested for staining before any urushi is applied.

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What goes wrongThe crack does not run the full height of the bowl, so it cannot simply be opened and glued as a two-piece repair. A related risk identified is that urushi may stain the glaze or other surfaces if not tested first. A commenter who used epoxy on earlier projects also notes that the gold veins bulged noticeably, and that holding the pieces in place during the short epoxy cure window was the hardest part.

What recovers itFor the partial crack: scrub the fissure clean with soap and water, allow several days for all moisture to evaporate, trace the crack with ganshin-urushi (mugi-urushi further diluted with ki-urushi and turpentine to a wicking consistency), let it soak in for a few minutes, wipe away excess, and cure in the muro for one to two weeks before continuing with sabi, nakanuri, and gold. For the missing fragment: build an internal structure from several layers of hemp gauze bonded with urushi, then fill and level with kokuso followed by sabi until flush with the surrounding surface.

01

Clean and dry the crack

Scrub the crack as clean as possible with soap and water. Allow several days for all water to evaporate completely before applying any urushi.

the comment this came from ↗
02

Wick in ganshin-urushi

Trace the crack with ganshin-urushi—mugi-urushi further diluted with additional ki-urushi and turpentine to a consistency fluid enough to wick into the fissure. Let it soak in for a few minutes, then wipe away the excess.

the comment this came from ↗
04

Apply standard kintsugi layers

Proceed with the usual sequence: sabi putty to build up the repair line, nakanuri coats, and finally the gold application.

the comment this came from ↗
05

Build an internal structure for a missing fragment

Glue together several layers of hemp gauze with urushi to form a structural core inside the gap. Build up the surface with kokuso, then sabi, until the repair is flush with the surrounding ceramic.

the comment this came from ↗
··Reported

What was reported

  • A partial crack in a thick-walled ceramic bowl can be repaired with urushi without completing the break into two separate pieces, provided the walls are thick enough and the crack is not too deep. ↗
  • Ganshin-urushi is mugi-urushi further diluted with additional ki-urushi and turpentine to achieve a fluidity that allows it to wick into narrow cracks. ↗
  • The glaze and any other surface on the piece must be tested for susceptibility to staining before urushi is applied. ↗↗
  • A missing ceramic fragment of significant size is considered an advanced kintsugi project requiring an internal structural support. ↗↗
  • A commenter who used epoxy for earlier kintsugi projects found the gold veins bulged noticeably and that the short cure window made holding the pieces together the hardest part; they speculated the slower urushi cure might actually reduce that particular difficulty. ↗
  • The slow cure of traditional urushi presents its own set of practical difficulties, distinct from the fast-cure issues of epoxy. ↗
  • A family heirloom is not an appropriate first project for a kintsugi practitioner; inexpensive practice pieces should be used first. ↗↗
  • The crack in the specific bowl in question stops at the foot ring on the underside and does not run the full height of the piece. ↗↗

Limits of this source

What the thread does not answer.

  • Whether the specific heirloom bowl will ultimately be repaired with urushi or whether the practitioner will seek professional help; the thread ends with a promise to post results but no outcome is recorded.
  • The best practical method for infilling a missing ceramic fragment of significant size—tape-forming, 3D-printed form, or freehand—remains unresolved beyond the gauze-and-kokuso structural suggestion.
  • How the slow-cure characteristics of urushi interact with the practical challenges of a large (30–40 cm) bowl, such as handling, humidity control, and the risk of the piece shifting during the one-to-two-week cure, is not addressed.
Read the documented methods →