漆Urushi Archive

Reported practice · r/Kintsugi

Reassembling a broken porcelain ashtray: adhesive selection and technique for a first repair

A first-time repairer needs to reassemble a broken porcelain ashtray of deep sentimental value and is weighing kintsugi (urushi-based), two-part epoxy, and cyanoacrylate (super glue) as the joining method. The fracture is relatively clean and the piece is a low-stress object (an ashtray), but the emotional stakes make a failed attempt costly.

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 allergic reaction (urushiol dermatitis) that appears 24–72 hours after exposure. Gloves and full coverage are essential when handling it.

Two-part epoxy resins contain toxic monomers in both the resin and the hardener before mixing. Nitrile gloves (not latex) and an A2-filter respirator for organic vapours are recommended. The claim that epoxy toxicity is not absorbed through skin is contradicted by the distributor guidance cited in the thread.

What the thread establishes

The answer.

The thread converges on cyanoacrylate as the most accessible option for a first attempt on a low-load porcelain item, noting that it bonds well to ceramic and sets in under a minute, which makes alignment the critical skill. Two-part epoxy is offered as an alternative when more working time is needed (roughly 8–10 minutes of holding), though it will leave a slightly domed seam and tends to read as plasticky if not finished well. Kintsugi with urushi is acknowledged as the traditional and most aesthetically rewarding path but is repeatedly flagged as too demanding for a first project on a piece this important. Practical consensus includes: practise on a disposable bowl first, use masking tape to hold alignment rather than relying on hand pressure, manage adhesive viscosity to avoid seepage or gapping, and dry-fit the pieces several times before applying any adhesive.

—

What goes wrongThe primary risk is irreversibility: once the adhesive cures, the pieces cannot be repositioned without re-breaking the object, and the new fracture will not follow the original line. A secondary concern raised by the poster is that a smooth, clean fracture surface might not give the adhesive enough mechanical grip, though this is disputed by other commenters who note that ceramic provides sufficient micro-texture. Cyanoacrylate can also seep out of the joint and bond to surrounding glaze, creating a mess that is difficult to clean.

What recovers itIf cyanoacrylate squeezes out of the joint, a craft razor can be used to trim the excess once it has fully cured, provided the surface is glazed. If the repair is simply wrong, the only option is to re-break the piece and start over, with no guarantee the fracture will repeat the same path. Solvent removal is mentioned as theoretically possible but introduces the risk of damaging the glaze, making it a last resort.

01

Analyse the adhesive before starting

Understand whether your chosen adhesive is thin (prone to running out of the joint) or thick (prone to leaving gaps) so you can compensate in application technique.

the comment this came from ↗
02

Prepare a calm, undistracted workspace

Work in a quiet place and spend roughly 15–20 minutes on breathing or relaxation exercises so that hand tremor and rushing do not compromise alignment.

the comment this came from ↗
03

Dry-fit and memorise the assembly

Seat all broken pieces together without any adhesive, study how they interlock, and repeat the seating motion several times to build hand-eye coordination and muscle memory before the real attempt.

the comment this came from ↗
··Reported

What was reported

  • Epoxy repairs on pottery tend to look cheap and plasticky and rarely turn out well. ↗
  • Kintsugi with urushi is the traditional and most aesthetically rewarding repair method but is widely advised against as a first project on a deeply sentimental piece. ↗↗
  • Cyanoacrylate (super glue) bonds effectively to ceramic and porcelain and sets in under one minute. ↗↗
  • Two-part epoxy requires approximately 8–10 minutes of holding time to seat flush. ↗
  • Epoxy will always leave a slightly raised or domed seam due to surface tension. ↗
  • The timing for dusting gold or bronze powder onto epoxy varies by brand and must be determined by experimentation. ↗
  • Strong masking tape can hold aligned pieces in place, eliminating the need for continuous hand pressure. ↗
  • Applying a thin layer of petroleum jelly (Vaseline) to adjacent areas creates a removable barrier that prevents unwanted adhesion. ↗
  • Excess dried cyanoacrylate on a glazed surface can be trimmed off with a craft razor. ↗
  • Once any adhesive (cyanoacrylate, epoxy, or urushi) has fully cured, the repair is effectively irreversible; undoing it requires re-breaking the piece, and the new fracture will not follow the original line. ↗
  • A successful repair should look beautiful to a viewer with no sentimental attachment to the object. ↗
  • Practising on a disposable or second-hand piece before working on the sentimental object is strongly and repeatedly recommended. ↗↗↗↗
≠Disputed

Whether cyanoacrylate or two-part epoxy is the better first-choice adhesive

The thread does not settle this
  • Cyanoacrylate is the right tool for a low-load porcelain ashtray; it bonds well to ceramic, sets fast, and a dollar-store tube is sufficient. ↗↗↗
  • Two-part epoxy or urushi is preferable because the longer working time (8–10 minutes) allows proper alignment; cyanoacrylate's speed makes it hard to control. ↗
  • Epoxy combined with gold dusting can produce a very attractive finish and is a legitimate alternative to lacquer, though it will always be slightly raised. ↗
≠Disputed

Whether a smooth, clean fracture surface is a bonding problem

The thread does not settle this
  • A smooth fracture may prevent the adhesive from gripping well; a rougher surface would be more ideal. ↗
  • Ceramic provides enough micro-texture ('tooth') for cyanoacrylate to bond effectively even on a clean break, and a clean fracture actually allows the pieces to seat with a minimal visible line. ↗↗

Limits of this source

What the thread does not answer.

  • The detailed procedure in the thread is cut off after step 4; the final steps (applying adhesive, curing, finishing) are not fully specified.
  • Whether the specific ashtray's glaze would be damaged by the solvents needed to remove a failed adhesive bond is raised but never resolved.
  • The optimal window for dusting gold or bronze powder onto a partially cured epoxy seam varies by product and is left to the practitioner's experimentation.
  • Whether the ashtray is in fact glazed (assumed by one commenter) or unglazed stoneware is never confirmed, which affects both adhesive choice and the feasibility of trimming excess with a razor.
Read the documented methods →