able experience is required before one is able to formulate the furnish of a paper consisting of two or more kinds of fibre, as the different fibres have varying dimensions and weights.
Printing Qualities.—The test for comparison with a standard paper is carried out by printing on the papers under examination at the same time, under the same conditions, and judging the brilliance, solidity of colour, absorption of ink, and noting how the colours dry. The test for the efficiency of sizing will have shown whether the paper is likely to be too porous or too hard, but the actual test for printing is advisable when taking a large quantity of a special making into stock.
The trouble of registering colour work has been dealt with at length elsewhere. If a paper has newly arrived from the mill, it is scarcely reasonable to condemn it on a trial for register before a little time has elapsed for maturing. It is well to examine the bulk to discover if all the supply is cut with the same machine direction.
Various Faults.—Paper which has not been properly retreed—that is, the extraction of faulty sheets has not been done closely—will be found unsuitable for the highest class of work. The faults in the sheets may comprise spots, specks, creases, superficial markings and torn paper. The spots and specks may be caused by various foreign substances—sand, dirt, knots of fibre, pieces of rubber, sealing-wax, little lumps of mineral matter or froth. The foreign matter varies with different papers, and will be more apparent in super-calendered papers than in those which are not highly rolled, as the rolling brings faults into greater prominence. Creases formed before or during calendering render sheets unfit for use. Superficial markings may occur at the drying cylinders or from marks on the other rolls, resulting in rust marks, streaks, and
