Also 礬沙, 陶砂. Sizing. Dōsa is made by dissolving animal glue, *nikawa 膠, in hot water, adding alum, boiling, and then adding cold water and cooling. It is used to coat paper and silk before painting to prevent ink and colors from running. The formula for mixing dōsa varies according to the season and the materials to be used. Untreated handmade Japanese paper, *washi 和紙, is highly water absorbent. Inks consisting of small particles such as black carbon ink, *sumi 墨, are absorbed and fixed between the paper fibers, but large particles of Japanese pigments, *ganryō 顔料, remain on the surface while the nikawa solution used as a binder, *baizai 媒剤, is absorbed. The pigment particles are not fixed to the picture surface, and unwanted blotting and spreading can occur. The dōsa layer solves this problem by reducing the water absorption of the paper. Applying dōsa is known as dōsabiki 礬水引き, and paper sized with dōsa is known as dōsagami 礬水紙.