Page:Paper and Its Uses.djvu/56

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PAPER AND ITS USES

ing can be obtained if the fibres have been carefully beaten and blended. Papers containing mechanical wood are classed as common printings, and are suitable only for common work. A small proportion of mechanical wood may not be noticeable in the finished paper, but when a large proportion is used, greyness of colour and poorness of appearance are sure indications of the low quality of the material. Hand- and mould-made papers have no mineral filling in their composition. For machine-made papers the addition of a small proportion enables them to take a very good finish. The amount of china clay present in the finished paper should not exceed 10 per cent, of the total weight.

Hand-made and mould-made printings are tub-sized and plate-rolled, without giving a high glaze to the paper. Machine-made printings are engine-sized, hard or soft according to the use to which the paper is to be put, and sometimes the surface will govern the sizing, some papers being hard-sized and super-calendered, others soft-sized and with only machine finish. As a matter of fact, super-calendered printings are used largely for illustrated work, and with half-tone blocks the ink must dry thoroughly and fairly quickly, so the paper is not hard-sized. All thin printings require to be well sized to prevent the ink sinking right through the paper, and most papers with machine finish, excepting the commoner news, are usually well sized, and coloured printings, too, incline to hard-sizing.

The best Bible papers are made of rag fibres with a fair amount of loading, and some starch to ensure opacity and good printing qualities. The Oxford India paper is still manufactured under special conditions which are kept secret, but there are many imitations which serve excellently for the purpose of thin paper editions. The graphic demonstration of the difference