DYEING 129
perhaps new cuttings, which brings up his costs and may absorb his profit for
that making. In the meantime, as he must keep his machine running, he will
have on his hands .the paper made the dull shade when starting up, the
'coloured' paper and the paper made with the more expensive furnish, which
may or may not be correct.
Thus the lot will have several 'shades', of which he will be notified in
due course by the salle foreman, the paper salesman, the customers and his
employer, all of whom will receive his explanations with obvious incredulity-
Paper made from uncoloured rag stock has a creamy tint. If the paper is
desired to be whiter, we have to add colour to the stuff in the beater. The
dye generally used is ultramarine blue.
This colour when used in small quantities gives a bluish-white tint, verging
on green in some qualities. If the tone is desired to be creamy white, some
pink must also be added.
Cheap printing papers and other papers made chiefly from mechanical
wood are coloured with aniline dyes. The shades obtained with this mixture
of blue and pink are infinite in number. The higher the quality and purity
of the fibres, the less dye is required and the more brilliant is the colour. With
good cotton fibres J oz. in 200 Ib. of stuff makes a decided shade, but that
quantity would have little or no effect on wood pulp.
When we get to 3 or 4 oz. ultramarine blue in 200 Ib. of stuff, the paper
begins to show an azure tint, which gets deeper as more blue is added, until
we arrive at what is called in the trade 'yellow*—Le. half-way between azure
and blue. Here again pink is employed to tone the azure to a richer shade
as required.
The beating of the stock has a great influence on its retention or absorption
of dyes. Free-beaten stuff requires more colour than fibrillated stuff. As no
two beatermen beat exactly alike in making, the shade will probably vary as
the differently treated stuff comes to the machine.
Other causes which produce differences in shade are insufficient or irregular
bleaching, lighter or heavier filling in of the beaters, different shades of 'broke*
in the furnish, careless weighing or measuring of the dyestuffs, too prolonged
beating, insufficient or too much sulphate of alumina and resin size, dyes not
thoroughly mixed with the stuff in the beater, stuff lying too long in the chests,
agitators running too fast or too slow, changes made in amount of water used
on the machine, and variations in weight, suction, couching, pressing, tub-
sizing, damping or finishing.
Those mills which use surface or river water are subject to variations of its
purity, which makes it very difficult to get the same colours in summer and
winter seasons or in flood times. Where a machine has to run from one stuff