Repairing a broken ceramic handle with internal steel pins and kintsugi finish

What goes wrongThe handle has fractured completely. Because the crack faces on a handle are small, the joint must carry significant tensile and shear load when the mug is lifted, so a simple adhesive bond without mechanical reinforcement is inadequate. Additionally, the translucent crackled glaze is prone to wicking and staining from urushi during assembly and levelling, which would mar the surface permanently.

What recovers itMechanical reinforcement with internal stainless-steel pins provides the necessary strength while keeping the external gold line thin. The glaze is shielded by a food-grade shellac coat applied to all external surfaces (but not the crack faces) before any urushi is mixed or applied. A thin initial urushi seal on the mating surfaces prevents the mugi-urushi from being absorbed into the body and showing through the translucent glaze. The shellac is removed after the sabi layer is in place so that subsequent nakanuri and gold can bond to the glaze.

Transfer pin locations to both crack faces

Dab small dots of red urushi at the intended pin positions on one crack face. Seat the two pieces together and squeeze the crack closed so the dots print onto the mating face. Both halves now carry matching marks for drilling.

Protect the glazed exterior with shellac

Paint the external surfaces of each fragment with food-grade shellac, taking care to keep it off the crack faces. This barrier stops urushi from wicking into the crackle pattern and from staining the matte glaze during assembly and levelling.

Drill pin holes with diamond burrs, kept wet

Using a small rotary tool (or a Dremel) fitted with diamond burrs on a 3/32-inch shank, drill the pin holes. Dab water onto the surface frequently and maintain a small pool to keep the cut cool and prevent glaze damage. The holes must be slightly larger than the pin diameter so the pieces can still mate tightly while the mugi-urushi fills the gap around the pin.

Seal the mating surfaces with a thin urushi coat

Apply a thin initial layer of urushi to the crack faces to seal the porous body. This prevents the mugi-urushi from being absorbed into the ceramic and showing through the translucent glaze once cured.

Dry-fit, then assemble with mugi-urushi and pins

Perform several dry fits to confirm that the pins seat correctly and the pieces close tightly. When ready, mix the mugi-urushi, insert the pins, and close the joint in one careful motion. The mugi-urushi must completely fill the annular space around each pin so that, once cured, the pin is locked and cannot shift. Avoid repeated handling after the mugi is mixed.

Build up the joint with sabi-urushi

Apply sabi-urushi over the pin area and the crack line to fill and level the joint. Because the shellac already protects the glaze from staining, a standard sabi mix is sufficient; a cleaner maki-ji variant is not needed.

Remove the shellac

Strip the shellac from the external surfaces. It must be gone before the nakanuri and gold are applied, because it would prevent those layers from adhering to the glaze.

Apply black nakanuri

Lay down two to three coats of black nakanuri over the repair area, allowing each coat to cure before the next.

Finish with gold powder

Apply maru-fun (round gold powder) over the cured nakanuri to create the visible kintsugi line. If the crackled glaze makes maru-fun application prone to staining, switch to a finer hiragoku-fun instead.

What was reported

• Handle repairs on ceramic vessels are structurally harder than body repairs because the crack faces present a small bonding area while the joint must resist substantial tensile and shear load during normal use. ↗
• Internal stainless-steel pins provide sufficient mechanical reinforcement for a handle joint while allowing the externally visible gold line to remain thin and subtle. ↗
• Red urushi can be used as a transfer medium to mark identical pin locations on both sides of a crack: dots dabbed on one face print onto the mating face when the pieces are squeezed together. ↗
• Food-grade shellac applied to the external glazed surfaces (but not the crack faces) prevents urushi from wicking into a crackle pattern and from staining a matte glaze during assembly and levelling. ↗
• A thin initial urushi seal on the mating surfaces is necessary to stop mugi-urushi from being absorbed into the ceramic body and becoming visible through a translucent glaze. ↗
• Drilling pin holes in glazed ceramic should be done with diamond burrs in a rotary tool, kept wet with a small pool of water to manage heat and protect the glaze. ↗
• Pin holes must be cut slightly larger than the pin so the pieces can still close tightly, but the mugi-urushi must completely fill the gap around the pin so it is locked in place once cured. ↗
• Several dry fits should be performed before mixing mugi-urushi to confirm that the pins and pieces seat correctly, because the assembly must be done in one careful pass without repeated handling. ↗
• The shellac barrier must be removed before nakanuri and gold are applied, because it would prevent those layers from adhering to the glaze. ↗
• A standard sabi-urushi mix is adequate for the putty layer when shellac is already protecting the glaze, making a cleaner maki-ji variant unnecessary. ↗