Persimmon Shibu Waterproofing & Suspended Cedar Fittings for Exterior Chochin

For centuries before the advent of petrochemical resins, Japanese craftsmen relied on kakishibu as an all-natural waterproofing agent, wood preservative, and textile dye. Kakishibu is produced from the juice of unripened, astringent persimmons (typically wild varieties such as Diospyros kaki var. sylvestris) harvested in late summer when tannin concentration is at its peak.

The bitter green fruit is crushed, mixed with water, and allowed to ferment naturally in large wooden vats for two to three years. During fermentation, wild yeasts and microbes break down sugars while condensing the plant's high-molecular-weight polyphenols (known chemically as shibuol). When brushed onto the porous washi paper of a chochin, the shibuol molecules penetrate the amorphous regions of the cellulose fibers and form robust cross-linking hydrogen bonds. As the treated lantern dries in sunlight, oxygen and ultraviolet light polymerize the tannins into a water-insoluble, tough, and leathery barrier that shields the paper from driving rain, airborne mold, and mildew.

For lanterns subject to severe maritime precipitation or continuous year-round outdoor exposure, artisans often augment or replace the kakishibu treatment with egoma-abura (perilla seed oil, Perilla frutescens). Unlike drying oils such as linseed, cold-pressed perilla oil contains high concentrations of alpha-linolenic acid, allowing it to polymerize rapidly into a tough, glass-like, transparent protective film upon exposure to air and sun.

Craftsmen warm the oil slightly and apply it in thin, uniform coats with silk pads. The oil saturates the washi fibers, dramatically increasing their translucency so that the lantern glows with a warm, brilliant amber intensity when lit from within. For ceremonial processional lanterns, artisans sometimes blend perilla oil with melted sumac berry wax (haze-ro), creating a smooth, matte hydrophobic surface that sheds rain droplets instantly without water spotting.

The structural terminals of a chochin lantern are anchored by two precision-turned wooden collars: the upper kasa (cap or crown ring) and the lower soko (base ring). These components are turned on a woodworking lathe from seasoned, slow-grown Japanese cedar (Cryptomeria japonica, or sugi) or hinoki cypress (Chamaecyparis obtusa).

The upper collar must fulfill several critical architectural functions. It must incorporate a central opening large enough to accommodate an interior candle spike (rousoku-tate) or modern electrical fixture while providing an exterior stepped lip that deflects rainwater cascading down the suspension cord. On its underside, the collar is machined with a precise annular groove (rebate) into which the top bamboo higo rib and the folded margins of the washi paper are tucked, glued, and secured with miniature copper tacks. The lower base collar is turned slightly thicker and heavier, providing ballast that stabilizes the lantern against sway in gusty winds.

In traditional Japanese urban architecture, exterior chochin lanterns are not merely decorative objects; they are vital functional elements integrated into the facade of the machiya (merchant townhouse) or temple compound. Suspended directly beneath the deep, projecting cedar eaves (nokisaki), the lantern marks the transition between the public street and the semi-private entrance portico.

To hang the lantern safely, blacksmiths fabricate hand-forged wrought iron or brass bails (kanagu) that arch over the top cedar collar. These bails attach to custom-carved timber cantilever arms (chochin-kake) mortised directly into the horizontal facade beams of the building. The forged hardware incorporates swivel eyes that allow the lantern to rotate freely in swirling drafts without twisting and fatiguing the suspension cord. Furthermore, during typhoon season, the entire assembly can be detached with a single motion, collapsed into a flat disk, and stowed safely inside the cedar entryway until the storm passes.