Dosabiki (sizing) is the technique of treating washi and eginu (silk canvas) used as the support medium for Japanese paintings, to prevent the ink from smudging.

This is done on “raw” washi and various other support elements. Sizing is best carried out in fine weather. It does not work very well when it is rainy or humid. If the temperature of the sizing solution is high, it leaves a gloss on the surface of the washi paper, so the best temperature is said to be around body temperature. However, if that does not work well, a higher temperature solution should be used.

To carry out dosabiki, spread the washi paper on a rug or a blanket. If the washi paper curls up, do not try to spread it out forcibly. It will spread out naturally when the sizing solution is applied. Use a wide brush to apply the sizing solution in one direction,　starting from the top of the front side of the paper. For the first coat, apply plenty of sizing solution and move the brush slowly because the washi is very absorbent. Apply a constant amount, making sure there are no breaks in the lines. Load the brush repeatedly, before the sizing solution on the brush runs out. Ensure that the brush marks not to overlap too much and also that there are no gaps. Once the sizing solution on the front surface of the paper has dried completely, apply a second coat in the same way, this time on the back side. From the second coating onward, there is no need to apply too much sizing solution as the paper is now less absorbent. (It is considered best to do this on the front, back and the front again, in that order.) With thin Mino paper and eginu, the sizing solution should be diluted to half the concentration and applied once respectively on the front and back.