By ERNEST EDWARDS, B.A.
A question, relative to the subject of reproducing negatives, which was
put at a meeting of one of your New York societies, prompts me to make a
few remarks on the subject.
Among the numerous and widely diversified ramifications of our business
(the Heliotype Printing Company) we have very often to reproduce and
multiply negatives in both a direct and reversed form. Various methods
for doing this have been tried, and I may here say that I am quite well
aware of all the methods that have hitherto been suggested for the
purpose, but that which I am to describe is the one to which preference
has been given, and which is that known as the carbon process.
A sheet of carbonized paper or "tissue," having been sensitized by
immersion in a bath of bichromate of potash, is dried in the dark and
placed away for future use, although it is undesirable that it be kept
for more than four or five days. This is placed in a printing frame in
contact with the negative and exposed for a few minutes, after which it
is immersed in water, squeegeed down upon a glass plate, and developed
with warm water in the way so well known to carbon printers. The result
is a transparency which, owing to having received a sufficient exposure,
should show every detail of the negative. The nature of the tissue
employed for such a purpose must be such as to give no strong contrasts,
but everything reproduced with soft and fine gradation of tone.
The transparency thus obtained forms the _cliché_ by which the negatives
are subsequently made; and a negative of any size may be obtained by
the camera on wet or dry plates. The transparency must, of course, be
pointed to the sky and the light transmitted through it, no other light
being allowed to reach the lens except that which passes through the
carbon transparency. Care must also be taken that the transparency is
_uniformly_ lighted. If it is not possible to obtain a northern light,
which is best, a reflector of white paper or card may be used which must
be sufficiently large and placed at an angle of about forty-five degrees
to the transparency.
If the repeated negative is to be of the same size as the original it
may be readily produced by repeating the operation of printing on carbon
tissue, using the transparency in place of the negative, or using a dry
plate in place of the tissue. But on the whole I have satisfied myself
that the best results are to be obtained by the first method. There is
a greater softness in the latter method, but a greater character and
similarity to the original in the former method. There is no doubt that
the use of the carbon transparency removes the hardness and riffidness
of the outlines peculiar to the older method of a collodion
transparency, while with carbon as the medium it is difficult for
any but the most experienced eye to distinguish the copy from the
original.--_Photo Times._
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