pass before you print it. This
process is called "fuming," and consists in exposing the paper to the
fumes of ammonia for a short time.

A fuming-box is needful, but one can easily be constructed, without the
expense of purchasing this convenience. Take a wooden box about two feet
cube, and, with hinges, make a door of the cover. Close all the cracks
with strips of cloth so that the box will be both light and air tight,
and fasten corresponding strips around the edges of the door so that no
light will make its way in there.

Stretch two or three strings across the box near the top, on which to
hang the paper that is to be fumed, and put a small flat dish in the
bottom of the box.

When you are ready to fume your paper, pin two sheets together, back to
back, and hang them on one of the strings. Several sheets can be fumed
at once in this manner. Fill the dish with ammonia, and closing the door
tightly, let the paper absorb the fumes for fifteen or twenty minutes.

After fuming, the paper should be given a short time to dry before it is
used for printing. It should then be put in the printing frame in the
same way as the cyanotype paper and exposed to the sun.

If your negative is a thin one, a diffused light is better for printing
than the direct rays of the sun. Diffused light is a strong light that
is not sunlight.

If the negative is exceedingly thin, the light indoors, away from the
window, will be sufficient. Satisfactory results cannot of course be
achieved with too thin a negative, but this diffused light will give the
best print that you can obtain.

In examining the print from time to time be sure that you do not open
both sides of the printing frame at once, for if you should do this, you
will find it impossible to replace the print in exactly the same
position, and so it will be spoiled by being printed with double lines.

No exact rule can be given for the length of time which should be
allowed for the printing of a negative. It should, however, be allowed
to become twice as dark as it ought to be after the picture is toned and
mounted. The after processes of toning bleach the print very much, as
the amateur will discover for himself.

If a negative is very dense or thick, as over-development will sometimes
cause it to become, the time for printing will be considerably extended.
While in a good light, with a negative of the right density, five
minutes or less is sufficient to print a negative, three