stick of ink being pressed
_lightly_ upon the saucer and moved quickly, the grinding being
continued until the ink is mixed quite thickly. This will grind the ink
fine as it is mixed, and more water may be added to thin it. It is best,
however, to let the ink be somewhat thick for use, and to keep it
covered when not in use; and though water may be added if it gets too
thick, yet ink that has once dried should not be mixed up again, as it
will not work so well after having once dried.

Of liquid inks the Higgins ink is by far the best, being quite equal to
and much more convenient for use than the best stick ink.

The difference between a good and an inferior India ink lies chiefly in
the extent to which the lamp-black, which is the coloring matter, forms
with the water a chemical solution rather than a mechanical mixture. In
inferior ink the lamp-black is more or less held in suspension, and by
prolonged exposure to the air will separate, so that on being spread the
solid particles will aggregate by themselves and the water by itself.

This explains why draughtsmen will, after the ink has been exposed to
the air for an hour or two, add a drop of mucilage to it; the mucilage
thickening the solution, adding weight to the water, and deferring the
separation of the lamp-black.

A good India ink is jet black, flows easily, lies close to, does not
stand upon or sink into the paper, and has an even lustre, the latter
being an indication of fineness. The more perfect the incorporation of
the lamp-black with the water the easier the ink will flow, the less
liable it is to clog the instruments, the more even and sharp the edges
of the lines, and the finer the lines that may be drawn.

Usually India ink can only be tested by actual trial; but since it is
desirable to test before purchasing it, it may be mentioned that one
method is to mix a little on the finger nail, and if it has a "bronzy"
gloss it is a good indication. It should also spread out and dry without
any tendency to separate.

The best method of testing is to mix a very little, and drop a single
drop in a tumbler of clear water. The best ink will diffuse itself over
the surface, and if the water is disturbed will diffuse itself through
the water, leaving it translucent and black, with a slight tinge of
bronze color. A coarser ink will act in a similar manner, but make the
water somewhat opaque, with a blue-black, or dull, ashy color. A still
coarser ink will,