_Multiplying Negatives._--In reply to M. N. S. (Vol. ix., p. 83.) I
would suggest the following mode of multiplying negatives on
glass, which I have every reason to believe would be perfectly
successful:--First, _varnish_ the negative to be copied by means of DR.
DIAMOND'S solution of amber in chloroform; then attach to each angle,
with any convenient varnish, a small piece of writing-paper. Prepare a
similar plate of glass with collodion, and drain off all superfluous
nitrate of silver, by standing it for a minute or so on edge upon a
piece of blotting-paper. Lay it flat upon a board, collodion side
upwards, and the negative prepared above upon it, collodion side
downwards. Expose the whole to daylight for a single second, or to
gas-light for about a minute, and develope as usual. The result will be
a _transmitted positive_, but with reversed sides; and from this, when
varnished and treated as the original negative, any number of negatives
similar to the first may be produced.
The paper at the angles is to prevent the _absolute_ contact and
consequent injury by the solution of nitrate of silver; and, for the
same reason, it is advisable not to attempt to print until the primary
negative is varnished, as, with all one's care, sometimes the nitrate
will come in contact and produce spots, if the varnishing has been
omitted. Should the negative become moistened, it should be _at once_
washed with a gentle stream of water and dried.
I have repeatedly performed the operation above described so far as the
production of the positive, and so perfect is the impression that I see
no reason why the second negative should be at all distinguishable from
the original.
I am, indeed, at present engaged upon a _similar_ attempt; but there are
several other difficulties in my way: I, however, entertain no doubts of
perfect success.