Naka-nuri: Middle Coats

With the ground built and flattened, middle coats bridge the rough structural ji-nuri layers and the refined top coat. Naka-nuri urushi is a specific grade for this stage: summer-harvested sap that's been hand-stirred in vats to reduce water content and thicken it for these first pure (unfilled) coats. (Suzanne Ross, Urushi FAQs) Conservation surveys of historical Japanese lacquerware note that the overall build from ground to finished surface commonly runs to more than 20 thin coats, each cured first at high humidity and then finished off in ambient air before the next goes on. (Conservation Wiki)

A concrete, documented middle-coat cycle, from a maker producing urushi fountain pens: black naka-nuri urushi brushed on and cured in a humidity chamber for 48 hours, then ground flat with charcoal and water — and that whole cycle repeated five times before moving to finer coats. (On Fountain Pens, guest post) That single documented example is worth internalizing: five full 48-hour cure-and-level cycles, for the middle stage alone, on an object the size of a pen barrel. Scale expectations accordingly for a bowl or tabletop.