Dosabiki

Dosabiki is the preparatory treatment of washi paper with a solution of alum (myoban) and animal hide glue (nikawa), known collectively as dosa. This sizing controls how the paper absorbs water-based pigments during printing. Unsized paper would soak up pigment like a sponge, causing colors to bleed and spread uncontrollably. Properly sized paper holds pigment on or near the surface, producing crisp lines and vibrant colors.

The dosa solution is brushed onto both sides of the paper and allowed to dry before printing. The ratio of alum to glue, and the number of sizing coats, are adjusted depending on the printing requirements. Paper for prints requiring fine detail and sharp color boundaries receives heavier sizing; paper intended for softer, more absorbent effects may be lightly sized or left partially unsized.

The quality of dosabiki significantly affects the final print. Uneven sizing produces inconsistent color density across the image. Over time, the dosa can break down, which is why old prints sometimes show foxing or color changes in areas where the sizing has deteriorated. Contemporary printmakers continue to use traditional dosa formulations, though some have experimented with synthetic sizing agents.