Fig. 16.—Section of colour-block. A. Colour mass. B. Depression. C. Surface of Plank.

When the register marks corresponding to these colour forms have also been cut, and the paper washed off the blocks, the clear spaces may be used for pasting down new key impressions for the smaller colour patches and their corresponding register marks. In this way one side of a colour plank may contain several different colour forms and sets of register marks. As a rule the different colour patches would be printed separately, though in some cases two colours may be printed at one impression if they are small and have the same register marks.

When the blocks have been cut and cleared it is advisable to smooth with sand-paper the edge of the depression where it meets the uncut surface of the wood, otherwise this edge, if at all sharp, will mark the print.

For any particulars about which one may be in doubt, the sets of blocks at South Kensington Museum or in the Print Room at the British Museum are available for examination. In one of the sets at the British Museum it is interesting to see the temporary corrections that have been made in the register marks during printing by means of little wooden plugs stuck into the register notches.

In nearly all cases the Japanese blocks were made of cherry wood, but planks of box are said to have been occasionally used for very fine work.