A New or Improved Sensitive Plate or Film, and a Method of Producing, Developing, Fixing, and Toning the same.
Year: 1897

page_text: A New or Improved Sensitive Plate or Film, and a Method of
Producing, Developing, Fixing, and Toning the same.
I, THOMAS CUNNINGHAM PORTER, of Eton College, in the County of Bucks,
Master of Arts, do hereby declare the nature of this invention to be as follows:-
The object of the present invention is to produce a plate or film suitable for
lantern slides or transparencies which will represent a picture in various shades
of blue, such film being particularly suitable for ice and snow scenes, clouds and
seascapes.
In carrying my invention into effect I take a plate or film coated with gelatine
or other suitable substratum and I immerse or place the same in contact with a
solution of ferric ammonium citrate or other ferric salt. I preferably employ a
strong solution of the ferric salt and immerse or place the plate or film in contact
for about three minutes. I then remove the plate or film and rapidly wash off the
excess of the solution with distilled water. The plates or films are allowed to dry
and are then ready for exposure, usually by contact with a negative in a strong
light.
They are developed by immersion in a solution of potassium ferricyanide and
fixed by washing first with dilute hydrochloric acid and then well washed with soft
or distilled water.
The positives thus produced are of a blue colour inclining to green but by
subsequently treating them with a bath of very dilute ammonia or other alkaline
hydrate, the blue colour changes to a violet blue and finally becomes a pale reddish
brown.
I find that one part of a solution of ferric ammonium citrate saturated at
ordinary temperatures to one of water is very suitable.
I also find that one gram of potassium ferricyanide dissolved in 8 c. c. of soft or
distilled water is suitable for development. The fixing solution is made with about
5 per cent. of pure strong hydrochloric acid the rest being water.
The toning solution contains about two drops of ammonia solution (880) to
the oz. of distilled water.

page_text: A New or Improved Sensitive Plate of Film, and a Method of
Producing, Developing, Fixing, and Toning the same.
I, THOMAS CUNNINGHAM PORTER, of Eton College, in the County of Bucks,
Master of Arts, 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 the present invention is to produce a plate or film suitable for
lantern slides or transparencies which will represent a picture in various shades
of blue, such film being particularly suitable for ice and snow scenes, clouds and
seascapes.
..
In carrying my invention into.effect I take a plate or film coated with gelatine
or other suitable substratum and I immerse or place the same in contact with a
solution of ferric ammonium citrate or other ferric salt. I preferably employ a
strong solution of the ferric salt and immerse or place the plate or film in contact
for about three minutes. I then remove the plate or film and rapidly wash off the
excess of the solution with distilled water. It is of great importance that the excess
of sensitizing solution should be washed off both immediately and rapidly. The
plates or films are allowed to dry and are then ready for exposure, usually by
contact with a negative in a strong light.
•
They are developed by immersion in a solution of potassium ferricyanide and
fixed by washing first with dilute hydrochloric acid and then well washing with soft
or distilled water.
The positives thus produced are of a blue colour inclining to green, but by
subsequently treating them with a bath of very dilute ammonia. or other alkaline
hydrate, the said colour changes to a violet blue, finally becoming a pale reddish
brown should the toning process be continued too long.
I find that one part of a solution of ferric ammonium citrate saturated at:
ordinary temperatures to one of water is very suitable for sensitizing.
I also find that one gram of potassium ferricyanide dissolved in 8 c.c. of soft or
distilled water is suitable for development. The fixing solution is made with about
5 per cent. of pure strong hydrochloric acid the rest water.
The toning solution contains about two drops of ammonia solution (.880) to
the oz. of distilled water.
Having now particularly described and ascertained the nature of my said in-
vention and in what manner, the same is to be performed, I declare that what I
claim is :-
...1. The. herein described method of producing a sensitive plate or film consisting
in immersing a plate or filim coated with gelatine or other suitable substratum in,
or placing the same in contact with, a solution of ferric ammonium citrate or other
ferric salt, and then immediately and rapidly washing off the excess of solution
from the plate or film with distilled or soft water, substantially as described and
for the purpose specified.
2. The manufacture and use of a sensitive plate or film produced as claimed.
3. The herein described method of producing a lantern slide or transparency
having a blue or violet blue colour consisting in immersing a plate or film produced
as claimed in a solution of potassium ferricyanide to develop the image, fixing

page_text: the image by washing with dilute hydrochloric acid and subsequent washing with
water, and finally toning in a bath of very dilute ammonia or other alkaline
hydrate, substantially as described.
E. P. ALEXANDER & SON,
Chartered Patent Agents,
19, Southampton Buildings, Chancery Lane, London, W.C., Agents.