Page:Paper and Its Uses.djvu/87

Rh aside the reams which are troublesome, and in time the electricity will disperse. The use of automatic feeding mechanism is sometimes quoted as a cure for this trouble.

Papers which are loose in texture are usually soft-sized, and thus, having comparatively little size to hold the fibres together, will give off fluff or dust, consisting of small fibres, as soon as the paper is subjected to friction, even of the lightest description. Such paper in its passage through the printing machine gradually deposits its fibrous dust upon the printing surface, the rollers take it from there to the ink distributing surface, and the whole of the inking and printing becomes foul. Such papers are extremely difficult for lithographic printing, and the letterpress printer consumes most of such papers. Soft papers with the mill cut are slightly rough and give off dust, and trimming a clean edge reduces the liability to fluff, but cleaning up at machine (forme, rollers, and ink slab or drum) will be necessary more frequently than is usual. When the machine is stopped for washing up, all parts of the machine carriage which can be reached should be wiped free from dust, as the accumulation will gradually find its way to the rollers when the machine is in motion.

The proper ink for the paper will prove the solution for difficulties in printing on hard papers, and also on very soft papers. It is outside the scope of this work to deal with printing inks, but in regard to coated papers it will be found that all such papers do not behave alike. Some take the ink readily and retain the fullness of colour, while others soak up the varnish and leave the dry colour on the surface. The latter fault is owing to the absorbency of the body paper, and ink must be treated so that the absorbency of the paper is satisfied, and yet the colour and medium remain more on the surface of the paper.