IMPROVE- MENTS IN PHOTOGRAPHIC PLATES
Year: 1856

page_text: LETTERS PATENT to John Johnston, of Ohio, in the United States of
America, and of No. 4, Trafalgar Square (Office for Patents), Charing
Cross, in the County of Middlesex, for the Invention of "IMPROVEMENTS IN
Sealed the 3rd March 1857, and dated the 5th September 1856.
PROVISIONAL SPECIFICATION left by the said John Johnston at the
Office of the Commissioners of Patents, with his Petition, on tho
5th September 1856.
I, JOHN JOHNSTON, of Ohio, in the United States of America, and of No. 4,
Trafalgar Square (Office for Patents), Charing Cross, in the County of
Middlesex, do hereby declare the nature of the said Invention of "IMPROVE-
MENTS IN PHOTOGRAPHIC PLATES," to be as follows:-
This Invention consists in substituting in lieu of plates of glass, as commonly
employed for taking photographic portraits upon, thin plates of any cheap
metal, for example, sheet iron, one side or surface of which is coated with
black japan; such japanned surface is to receive the collodion coating, in the
manner usually practised of coating plates of glass, with this advantage, that
whereas for positive pictures on glass the back of the picture requires to be
covered with black varnish to throw up the shadows, by this Invention, when
the image is developed, the japan back ground is at once exposed to view;
moreover, the improved plates may be afterwards readily cut to any desired
shape.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said John Johnston in the Great Seal Patent Office on the
5th March 1857.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
JOHNSTON, of Ohio, in the United States of America, and of No. 4, Trafalgar
Square, Office for Patents, Charing Cross, in the County of Middlesex, send
greeting.
WHEREAS IIer most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Fifth day of September, in the year of our Lord
One thousand eight hundred and fifty-six, in the twentieth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
John Johnston, Her special licence that I, the said John Johnston, my
executors, administrators, and assigns, or such others as I, the said John
Johnston, my executors, administrators, and assigns, should at any time agree
with, and no others, from time to time and at all times thereafter during the
term therein expressed, should and lawfully might make, use, exercise, and
vend, within the United Kingdom of Great Britain and Ireland, the Channel
Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN PHOTOGRAPHIC
PLATES," upon the condition (amongst others) that I, the said John Johnston,
my executors or administrators, by an instrument in writing under my or their,
or one of their hands and seals, should particularly describe and ascertain the
nature of the said Invention, and in what manner the same was to be per-
formed, and cause the same to be filed in the Great Seal Patent Office within
six calendar months next and immediately after the date of the said Letters
Patent.
NOW KNOW YE, that I, the said John Johnston, do hereby declaro
the nature of the said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement thereof, that is to say :-
My Invention consists in substituting in lieu of plates of glass, as commonly
employed for taking photographic portraits upon, thin plates of metal, for
example, sheet iron, one side or surface of which is coated with black japan,
such said japanned surface being intended to receive the collodion coating, in
the manner usually practised of coating plates of glass; the said japanned
metal plates possessing this advantage, that whereas for positive pictures
on glass the back of the picture requires to be covered with black varnish
to throw up the shadows, by this Invention, when the image or picture is

page_text: MODE OF MANUFACTURE.
I take a piece of sheet iron (charcoal iron by preference) and cut and roll it
to the desired size, length, and thickness by any of the known means of
rolling and cutting plate iron; I then subject one side of such said strips or
pieces of metal to the well-known process of japanning, as at present practised
of japanning metal, taking care to keep such japanned surface free from grease
of any kind. These japanned strips are then cut to the required width, in
accordance with the different sizes of plates used by photographic artists. In
using the above plates for taking pictures or portraits upon, the process is
similar in all respects to that hitherto employed in using glass, with this
advantage, that by the use of japanned metal plates the necessity for blacking
the back of the picture is dispensed with, and a better pictorial effect is pro-
duced by taking the picture directly upon the japanned black surface instead
of having the thickness of the plate between the picture and the black back
ground.
Having now described the nature and object of my said Invention of
Improvements in Photographic Plates," together with the best means I am
acquainted with for carrying the same into practical effect, I hereby declare
my Invention to consist in, and I claim, the making of photographic plates of
japanned metal instead of glass, as heretofore practised.
In witness whereof, I, the said John Johnston, have hereunto set my
hand and seal, this Thirteenth day of February, in the year of our
Lord One thousand eight hundred and fifty-seven.
Witness,
ALEX PRINCE, Agent for Patents,
4, Trafalgar Square, Charing Cross.
JOHN JOHNSTON. (L.S.)