been occasionally used for very fine
work.

ERRORS OF REGISTER

However exactly the register marks may be cut in a new set of blocks,
very puzzling errors occasionally arise while printing, especially if
the planks are of thin wood.

Some of the blocks are necessarily printed drier than others. For
instance, the key-block is printed with a very small amount of ink and
paste. Other blocks may be even drier, such as the blocks which print
small forms or details in a design. The blocks, however, which are used
for large masses of colour, or for gradated tones, are moistened over
the whole or a large part of the surface of the block, and if the wood
is thin, and not well mounted across the ends, the block soon expands
sufficiently to throw the register out. If the block is not mounted
across the ends there will also be a tendency to warp, and this will add
to the errors of register. But if the blocks are of fairly thick wood,
and well mounted, the register will remain very exact indeed.

Usually the key-block is printed first. If the subsequent blocks are not
in exact register the error is noticeable at once, and slight
adjustments may be made for its correction. But in cases where the
key-block is printed last (as sometimes is necessary) each colour block
must be tested before a batch of prints is passed over it. For this
purpose the first few prints of every batch should receive a faint
impression of the key-block, so that the register of the colour
impression may be verified before proceeding with the whole batch.

If these precautions are taken, and the entire set of blocks kept as
nearly as possible in the same conditions of dryness or moisture, all
difficulties of register in printing will be easily overcome.

When cutting a new set of blocks there is another possible source of
error which needs to be carefully guarded against. Most of the work in
designing a new print is necessarily spent in planning and cutting the
key-block, which may occupy a considerable time, especially if other
work has to be carried on as well. If new wood is used, or wood that has
not been seasoned long indoors, it will dry and contract considerably
across the grain before the work is finished. Then, if newer planks are
prepared and cut up for the colour blocks, and impressions from the
key-block are pasted down on them for cutting, it will be found that, as
the newer wood of the colour-blocks goes on drying, it will shrink out
of re