e
thick cloth, and then enough of the paper to see something of the forming
picture. If not printed dark enough as yet, we turn back to their places
successively the picture, the cloth, the opened part of the frame, and lay
it again in the sun. It is just like cooking: the sun is the fire, and the
picture is the cake; when it is browned exactly to the right point, we
take it off the fire. A photograph-printer will have fifty or more
pictures printing at once, and he keeps going up and down the line,
opening the frames to look and see how they are getting on. As fast as
they are done, he turns them over, back to the sun, and the cooking
process stops at once.

The pictures which have just been printed in the sunshine are of a
peculiar purple tint, and still sensitive to the light, which will first
"flatten them out," and finally darken the whole paper, if they are
exposed to it before the series of processes which "fixes" and "tones"
them. They are kept shady, therefore, until a batch is ready to go down to
the toning room.

When they reach that part of the establishment, the first thing that is
done with them is to throw them face down upon the surface of a salt bath.
Their purple changes at once to a dull red. They are then washed in clean
water for a few minutes, and after that laid, face up, in a solution of
chloride of gold with a salt of soda. Here they must lie for some minutes
at least; for the change, which we can watch by the scanty daylight
admitted, goes on slowly. Gradually they turn to a darker shade; the
reddish tint becomes lilac, purple, brown, of somewhat different tints in
different cases. When the process seems to have gone far enough, the
picture is thrown into a bath containing hyposulphite of soda, which
dissolves the superfluous, unstable compounds, and rapidly clears up the
lighter portions of the picture. On being removed from this, it is
thoroughly washed, dried, and mounted, by pasting it with starch or
dextrine to a card of the proper size.

The reader who has followed the details of the process may like to know
what are the common difficulties the beginner meets with.

The first is in coating the glass with collodion. It takes some practice
to learn to do this neatly and uniformly.

The second is in timing the immersion in the nitrate-of-silver bath. This
is easily overcome; the glass may be examined by the feeble lamp-light at
the end of two or three minutes, and if the surface looks s