ents, such as compounds of lead or manganese, by
means of which the oil is chemically affected, _i.e._ it is oxidized.
Such dryers, when added to printing ink, attracts the oxygen of the
air and transfer it by catalytic action to the varnish of the ink,
thus causing it to oxidize more rapidly, or to become, as it is
commonly called, dry.

Having disposed of the manufacture of the varnishes and dryers, we now
come to the manufacture of pigments. This is such a large field that
it can be only cursorily covered within the limits of a short article.
The pigments are of many kinds and classes. The blacks alone would
form a large chapter by themselves; yet all of them consist of carbon,
produced by the combustion of hydrocarbons of various kinds, and
according to their origin they are the so-called carbon blacks, lamp
blacks, spirit blacks, oil blacks, Frankfort blacks, etc., each of
which has its distinct and peculiar properties and value for its
specific purpose.

The other pigments fall naturally into two divisions,--chemical colors
and the so-called "lakes." The chemical colors are in general of
mineral origin, produced by the action of one chemical upon the other,
or in some cases by physical or chemical action upon earths and ores.
In the first group, we have such colors as vermilions, white lead,
chrome yellows, the ferrocyanide blues (Milori blues, bronze blues,
Prussian blues, Chinese blues, Antwerp blues, Paris blues, Berlin
blues), ultramarines, etc.; in the second group, such colors as
cyanides, umbers, Indian red, and many others.

The lakes are principally formed by the use of coal-tar derivatives,
and are usually incorrectly grouped as anilines. They are produced by
precipitating water-soluble dyes upon a suitable substratum or base.
Their shades, strength, brilliancy, permanency, and working qualities
are dependent upon the nature of the dye itself, upon the nature and
percentage of the substratum or base, and also upon the suitable
selection and manipulation of the precipitating agents. This class of
colors is to-day by far the most important of all, since through great
progress made in chemistry in recent years, it is possible to make
them of the greatest possible strength and permanency, together with a
brilliancy of shade which was for many years an ideal earnestly
striven for, but apparently impossible to accomplish.

Having thus considered the products which are the principal raw
materials of printi