Page:Paper and Its Uses.djvu/97

Rh made in machine-made papers. The smooth side of M.G. papers is the right side. M.G. poster papers are rougher on the wrong side to make the posting of the bills an easier matter.

The wire marks assist one in distinguishing between hand-made and machine-made papers. It is clear that all machine-made papers have a wire mark on the wrong side, even if laid or watermarked. The water-mark of the hand mould is fastened over the wire, so the watermark will never show wire marks. Looking through the paper, observe whether the watermark has any small woven wire marks; if it has, it is undoubtedly machine-made. A laid paper which shows woven wire marks is of course the product of the machine.

Coloured papers may vary in shade on the two sides. This variation is more frequently seen in papers which are coloured by pigments than in those dyed with aniline colours. Blue papers, with ultramarine in their composition, tend to be slightly lighter on the wrong side of the sheet. The causes of this are different in hand-made and machine-made papers. In hand-mades the colour has a tendency to gravitate to the bottom of the mould, which is the right side of the paper, while in machine-made papers the action of the suction boxes is apt to draw some of the colour away from the under side, leaving the right side slightly darker. Thus difference in shade of the two sides is not a guide to distinguish between hand- and machine-made papers.

To recall the methods of manufacture. The mould of hand-made papers receives a shake each way, felting the fibres evenly. The machine wire receives a side-shake which is only effective for a short period—as long as the pulp is in a state of suspension—and as soon as the water has drained away the shake ceases