OFFSETTING
No care need be taken to prevent "offsetting" of the colour while printing. The prints may be piled on the top of each other immediately as they are lifted from the block, without fear of offsetting or marking each other. Only an excessive use of colour, or the leaving of heavy ridges of colour at the edges of the block by careless brushing, will sometimes mark the next print on the pile. As in printing the key-block, it is well to hold the brush quite upright for the last strokes across the block, and always to give a full stroke across the whole length or width of the form to be coloured.
As soon as one colour-block has been printed, the next may be taken and printed at once, without fear of the colour running, even though the fresh colour touches the parts already printed.
One by one each colour-block is printed in this way until the batch of paper has been passed over the whole set of blocks composing the design of the print. There may sometimes be an advantage in not printing the key-block first, though as a rule it should come first for the sake of keeping the later blocks in proper register. If the key-block is not printed one cannot see how the colour-blocks are fitting. But in the case of a sky with perhaps two or even three printings—a gradation and a flat tone or two gradations—there is danger of blurring the lines of the key-block, so that in such a case the sky should be printed first, and then the key-block followed by the remaining colour-blocks.
At the end of a day's printing the prints may quite safely be left standing together between the boards until the next day. For three days the damp paper comes to no harm, except in hot weather, but on the fourth day little red spots of mould begin to show and spread. It should be remembered that freshly boiled paste is to be used each day.