Reported practice · r/Urushi
Whether a layer of textile should be applied to the inside of a lacquered bowl or similar vessel in addition to the outside, and what role the textile plays in each case.
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.
Raw urushi (ki-urushi) is a potent skin sensitiser; contact can trigger a delayed urushiol-type dermatitis that may appear 24–72 hours after exposure. When applying urushi to textile or putty grounds, wear nitrile or neoprene gloves and avoid skin contact with the wet film.
What the thread establishes
The decision depends on whether the textile is serving a decorative or a structural purpose. As a decorative texture (nuno-me), it is usually kept off the interior of bowls and other wet-food containers because the raised weave traps food, complicates cleaning, and accelerates wear of the urushi film; a relatively flat surface texture can be made food-safe, and the technique is in fact common on the interior of trays where it helps mask scratches. As structural reinforcement, the textile is applied to the interior as well: for open vessels the standard practice is to lay a strip along the rim and fold it over so the edge is covered on both faces, since the rim is the most likely fracture point. For boxes and jointed items, strips are laid along each joint and then additional full-surface layers are added, ideally on both faces, though a single side is acceptable if the wood grain is meant to show. The textile is most often hemp rather than linen, and an open-weave (gauze-like) cloth is strongly preferred so that urushi can penetrate and encase every thread through the full thickness of the weave; long-fibre Japanese paper is a lighter alternative for thinner reinforcement.
What goes wrongA tight or closed weave prevents urushi from penetrating the full thickness of the fabric, leaving the threads only surface-coated and prone to delamination. A raised decorative texture on a food-contact interior traps residue, forces more aggressive scrubbing, and gradually abrades the urushi layer.
Limits of this source