ne place. It is best to hold the print so that the water
runs off in the direction of the lines.

To dry the prints after washing they can be laid out flat in a moderately
warm oven, or before a stove, the heat of course not being sufficient to
cause the coating to peel.

To render the glue image more distinct the print should be immersed for a
few seconds in an aniline dye solution, the glue taking up the colour
readily. These dyes are soluble in either water or alcohol. A dye known as
"magenta" is very good.

The process of coating the metal sheets must be performed as quickly as
possible (about 10 seconds), as owing to the peculiar nature of the
bichromated glue it soon sets, and once this has taken place it is
impossible to smooth down any unevenness.

See that the negative and metal sheet make good contact while printing.

If the glue solution does not adhere to the surface of the foil in a
perfectly even film, but assumes a streaky appearance, a little liquid
ammonia, or a weak solution of nitric acid, rubbed over the surface of the
foil, which is afterwards gently scoured with precipitated chalk on a tuft
of cotton {124} wool, will remove the grease which is the cause of the
difficulty.

A photograph of a picture prepared from a line negative is given in Fig.
61. For a great many experiments, and in order to save time, trouble, and
expense, sketches drawn upon stout lead-foil in an insulating ink will
answer the purpose admirably, but if any exact work is to be done a single
line print is of course absolutely necessary. The insulating ink can be
prepared by dissolving shellac in methylated spirit, or ordinary gum can be
used. A very fine brush should be used in place of a pen, as the gum will
not flow freely from an ordinary nib unless greater pressure than the foil
will safely stand be applied. A sketch prepared in this manner is shown in
Fig. 62. A little aniline dye should be added to the gum to render it more
visible, or a mixture of gum and liquid indian ink will be found suitable.

[Illustration: FIG. 63.]

With the copying arrangement already described it is only possible to
employ it for reducing, it being necessary to employ a bellows camera with
a back focussing attachment for purposes of enlarging, and this constitutes
the chief drawback to the use of a fixed focus camera. By replacing the box
camera with a focussing camera of the same size, we shall have a piece of
apparatus capable of reducin