Improvements in the Carbon Process of Photographic Printing.
Year: 1891

page_text: Date of Application, 31st Oct., 1891-Accepted, 19th Dec., 1891
COMPLETE SPECIFICATION.
Improvements in the Carbon Process of Photographic Printing.
I MAX RAPHAEL, Manufacturer, of the Town of Breslau, in the Kingdom of
Prussia, do hereby declare the nature of this invention and in what manner the
same is to be performed, to be particularly described and ascertained in and by
the following statement :-
The object of this invention is to produce carbon-print pictures by a different
method than that heretofore adopted, that is to say, without the employment of the
customary carbon-papers, transfer-papers, and compression process, and from a
negative directly upon a mica-plate, prepared with carbon emulsion.
The process hereto followed in the preparation of carbon pictures, is only
practical if the picture which was originally taken upon carbon paper and after-
wards sensitised with bicromate of potassium, was subsequently transferred to
single or double transfer-paper, and from this on to glass or other material.
However in order to effect the transfer, other manipulations have heretofore been
necessary.
How much trouble and waste of time has been incurred by the process heretofore
followed, will be best ascertained by perusal of works of different authors, bearing
upon the subject.
One of the chief objections to the process heretofore practised, is that the picture
is produced in a reversed condition after exposure, and the correct picture only
obtained by transferring.
By my invention I propose to simplify the above process by pouring the carbon
emulsion direct on the mica-plate, allowing the same to dry, and afterwards
rendering the same sensitive by means of bicromate of potassium, so that on
exposure to light, the picture upon the negative is seen in its proper aspect.
This is obtained by printing the mica-plate reversed, that is to say, the printing
is not produced as heretofore by placing the sensitised surfaces in contact with each
other, but by placing the rear side of the mica-plate, or the unprepared surface,
upon the face of the negative; an exposure of this description is only possible
because the thickness of the mica-plate is considerably less than that of glass.
The direct copying of a negative upon a carbonized glass plate is not possible on
account of the thickness of the plate, and has not been attempted heretofore, as
only imperfect pictures would have resulted.
According to my invention, the entire process of carbon printing will resolve
itself into :-
1st. The sensitising of the emulsion on mica-plates, by a bath of bicromate of
potash.
2nd. Placing the sensitised mica-plate, with its unprepared surface upon the
prepared surface of the negative, when copying.
3rd. The exposure to light.
4th. The developement of the picture.
5th. The fixing of the picture by alum.
By my process, many of the usual operations may be dispensed with.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is:
The process for the production of carbon-prints, consisting in treating mica-
plates with carbon emulsion, and thereby dispensing with the use of the carbon

page_text: papers which have heretofore been necessary, and also with the squeezing
operation, substantially as hereinbefore described.
Dated this 31st day of October 1891.
HUGHES, SON & Co.,
38, Chancery Lane, London, W.C., Agents for the Applicant.