The colour blocks are planned and established by means of impressions taken from the key-block. For this purpose the register marks are inked[2] for printing as well as the design on the block, and the impressions must include both. These impressions are taken on thin Japanese paper, but not necessarily the thinnest tissue. If the thinnest is used, it should be pasted at the corners to a sheet of stiffer paper for convenience in handling.

It is then a fairly simple matter to take one of these key-block impressions and to make a plan of the various colour-blocks that will be required. These should obviously be as few as possible.

It is not necessary to provide an entire block for each patch of colour, but only the extent of surface required for each coloured portion of the print, as well as for its pair of register marks. Patches of different colour that are not adjacent to one another on the design of the print may be cut on the same block, provided they are not too close for free colouring of the block in printing. Each block also may be cut on both sides, so that there is considerable scope for economy in the arranging and planning of the colour blocks.

When the arrangement of the plan of colour has been simplified as far as possible, a new block is prepared as described above, and a sheet of thin Japanese paper (unsized) is cut large enough to cover the print design and its register marks. The clean surface of the new block is covered thinly with starch paste well rubbed into the grain, and while this is still wet an impression on the sheet of thin Japanese paper is taken of the entire key-block, including its register marks in black, and laid before it is dry face downward on the pasted surface of the new block. This should be done as already described on page 25. It should be rubbed flat with the printing pad and left to dry.

This operation requires careful handling, but it should be done easily and methodically, without any hurry.

Each side of the set of colour planks should be treated in the same way - a thin impression of the key-block and its register marks being laid upon each. It is advisable to paste down a freshly taken impression, each time, while the ink is still moist, for if these are allowed to dry, the shrinking of the paper causes errors of register.

When these new blocks are dry, the patch of colour to be cut on each surface should be clearly indicated by a thin wash of diluted ink or colour, but not so as to hide the printed key line.

The blocks may then be cut. A V-shaped cut is made round each form, as in the case of the key-block, and the clearing proceeds in the same way, but it is only necessary to clear a space of about an inch round each form: the rest of the wood should be left standing. A section of the printing surface of a colour block would be as follows:

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.