Improvements in or relating to Photographic Films or the like.
Year: 1892

page_text: Date of Application, 20th Apr., 1892
Complete Specification Left, 20th Jan., 1893-Accepted, 11th Mar., 1893
PROVISIONAL SPECIFICATION.
Improvements in or relating to Photographic Films or the like.
A communication from GEORGE EASTMAN, of Rochester, in the County of
Monroe, State of New York, United States of America.
I, ALFRED JULIUS BOULT of 323 High Holborn, in the County of Middlesex,
Member of the Institution of Mechanical Engineers, do hereby declare the nature
of this invention to be as follows:-
In the manufacture and use of photographic film such as is now in general use
consisting of a base or support of a nitro-cellulose gelatine or similar material,
provided with a sensitive coating, 'a considerable difficulty has manifested itself and
large quantities of film have been rendered worthless by reason of the streaks or
markings found in the sensitive coating upon development, caused by the sparks or
electrical discharges produced when the film is rolled or unrolled in the roll-holders
used for carrying it in long lengths, and also oftentimes during its manufacture and
subsequent treatment as when cut into strips or wound on the spools. These
discharges manifest themselves as sparks, which are sufficiently bright to fog the
sensitive emulsion in lines resembling discharges of static electricity, as seen for
instance in flashes of lightning or discharges from a static electrical machine.
When the film is practically exposed in the manufacture, it is rendered worthless
for negative making purposes and it is impossible to determine whether it has
been thus fogged until it has been developed, which is of course too late to save
the negative that contains these marks and it is therefore the object of the present
invention to obviate this difficulty and prevent the formation of these sparks or
discharges by rendering the film support non-electric, so to say, by the addition to
it of a suitable material which will not affect to any appreciable extent the quality
of the support as a support, or the sensitiveness of the emulsion, which is applied
to it.
After considerable experimenting my correspondent has discovered that if a
small quantity of a metallic salt, preferably one of the alkali nitrates, as nitrate
of potassium, or the nitrate of ammonium be added to the emulsion support it is
thereby rendered non-electric and the objectionable electrical manifestations will be
prevented both during the manufacture of the film, its subsequent treatment, and
when used in rcll-holders.
These discharges or sparks are particularly apparent when the method of making
film described in Letters Patent No. 19897 dated 10th December 1889 is practised,
said method consisting in depositing or spreading a nitro-cellulose compound upon
a plate glass support, the emulsion being afterward applied or coated upon it and
the whole after drying being stripped from the support.
When making film according to this Patent I prefer to incorporate in the nitro-
cellulose compound a small quantity of the nitrate of ammonium, the proportion of
which I have used with success being about ten (10) grains to the pound, but it is
obvious that a larger or smaller amount could be used if not in sufficient quantity
to affect the quality of the film or the film support.
In Letters Patent No. 19658 dated 2nd December 1890, I have described an
improved film consisting of a nitro-cellulose support sealed between two gelatine
coatings, one of which is the emulsion; said film being made by depositing upon a
plate glass table or support, first, a coating of insoluble gelatine, then a nitro-
cellulose compound, and finally the sensitive emulsion, the whole when dry being
stripped from the glass, and in making this film also a considerable amount is
rendered worthless by the electrical discharges produced when it is stripped froin
the glass, which, however, can be prevented by adding to the solution of gelatine

page_text: that is first deposited on the glass a quantity of the nitrate of potassium, and I
have used with success about fifty (50) grains to the pound, but as before stated,
a greater or less amount which would not affect the quality of the film may be
employed.
'
The film produced by this invention having what may be termed a non-electric
support is found to be practically free from the electrical markings and can be
wound and unwound and used in roll-holders of the usual or any preferred con-
struction, in long lengths, without liability of being damaged from these causes,
and small sheets or detached pieces of photographic film, the supports of which are
rendered non-electric, either during the methods of manufacturing just described,
or when manufactured by other methods, can be used without liability of being
affected in an objectionable manner.
While I have described one method of manufacturing the improved film and one
material that can be used with success, I do not wish it to be confined to either
of these, as other substances producing the same results can be used and other
methods of manufacture employed.
Dated this 20th day of April 1892.
ALFRED J. BOULT,
Chartered Patent Agent.
.
•
COMPLETE SPECIFICATION.
Improvements in or relating to Photographic Films or the like.
A communication from GEORGE EASTMAN, of Rochester, in the County of Monroe,
State of New York, United States of America.
I, ALFRED JULIUS BOULT of 323 High Holborn in the County of Middlesex,
M.I. Mech. E., and Chartered Patent Agent, 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 :—
In the manufacture and use of photographic film such as is now in general use
consisting of a base or support of a nitro-cellulose or similar compound, provided
with a sensitive coating of gelatino-argentic emulsion, a considerable difficulty has
manifested itself and large quantities of film have been rendered worthless by reason
of the streaks or markings found in the sensitive coating upon development caused
by the sparks or electrical discharges produced when the film is rolled or unrolled
in the roll-holders used for carrying it in long lengths, and also oftentimes during
its manufacture and subsequent treatment, as when cut into strips or wound on the
spools. These discharges manifest themselves as sparks, which are sufficiently
bright to fog the sensitive emulsion in lines resembling discharges of static
electricity, as seen for instance in flashes of lightning or discharges from a statio
electrical machine.
When the film is practically exposed in the manufacture it is by these lines
rendered worthless for negative making purposes and it is impossible to determine
whether it has been thus fogged until it has been developed, which is of course too
late to save the negative that contains these marks and it is therefore the object
of the present invention to obviate this difficulty and prevent the formation of these
sparks or discharges by rendering the film support "non-electric," so to say, by the
addition to it of a suitable material which will not affect to any appreciable extent
the quality of the support as a support, or the sensitiveness of the emulsion which
is applied to it.
After considerable experimenting it has been discovered that if a small quantity
of a metallic salt, preferably one of the alkali nitrates, as nitrate of potassium, or
nitrate of ammonium be added to the emulsion support it is thereby rendered non-
: electric and the objectionable electrical manifestations will be prevented both
during the manufacture of the film, its subsequent treatment, and when used in roll-
.holders.

page_text: These discharges or sparks are particularly apparent when the method of making
film described in British Letters Patent No. 19897 dated December 10th 1889, is
practised; said method consisting in depositing or spreading a nitro-cellulose
compound upon a plate glass support, the emulsion being afterward applied or
coated upon it and the whole after drying being stripped from the support.
When making film according to this Patent it is preferred to incorporate in the
nitro-cellulose compound a small quantity of the nitrate of ammonium, about ten
(10) grains to the pound giving successful results, but it is obvious that a larger
or smaller amount could be used if not in sufficient quantity to affect the quality of
the film or the film support.
While I prefer to use the above named salts, there are others that can be used
with good effect as they are salts having metallic bases, are soluble in the nitro-
cellulose solvents, for instance wood alcohol, and do not precipitate the materials
in the compound and are not themselves precipitated sufficiently to spoil the film,
so that the film support produced is non-electric, and is transparent or sufficiently
translucent for photographic purposes. These salts just referred to are potassium
acetate, sodium acetate, magnesium acetate and ammonium citrate, which can be
used in the proportion of one grain to the ounce of nitro-cellulose compound.
Sodium nitrate when used in the proportion of one-half grain to the ounce of the
compound will also produce the desired effect.
In British Letters Patent No. 19658 dated December 2nd, 1890, an improved
film is described consisting of a nitro-cellulose support sealed between two gelatine
coatings, one of which is the emulsion, said film being made by depositing upon a
plate glass table or support, first, a coating of insoluble gelatine, then a nitro-
cellulose compound, and finally the sensitive emulsion, the whole when dry being
stripped from the glass, and in making this film also a considerable amount is
rendered worthless by the electrical discharges produced when it is stripped from
the glass, which, however, can be prevented by adding to the solution of gelatine
that is first deposited on the glass a quantity of the nitrate of potassium, about
fifty (50) grains to the pound having been used with success, but as before stated,
a greater or less amount may be employed, so long as the quality of the film is not
affected.
As the proportion of the other ingredients employed in both the nitro-cellulose
compounds and the gelatine, and the apparatus and manipulations necessary to
manufacture the film have been described in the before mentioned and other
Specifications it is deemed unnecessary herein to specifically describe the same.
The film produced according to this invention having what may be termed a non-
electric support is found to be practically free from the electrical markings and can
be wound and unwound and used in roll-holders of the usual or any preferred
construction in long lengths, without liability of being damaged from these causes,
and small sheets or detached pieces of photographic film, the supports of which are
rendered non-electric, either in the methods of manufacturing just described, or
when manufactured by other methods, can be used without liability of being
affected in an objectionable manner.
While I have described one method of manufacturing the improved film it will
be understood that I do not wish to be confined to this, as with the same combination
of substances other methods of manufacture may be employed.
Having now particularly described and ascertained the nature of the said inven-
tion, as communicated to me by my foreign correspondent, and in what manner
the same is to be performed, I declare that what I claim is,-
"
1. A photographic film consisting of a "non-electric" support and a sensitive
emulsion substantially as described.
2. A photographic film consisting of a "non-electric" support composed of a
nitro-cellulose compound containing a metallic salt and a gelatino-argentic emulsion
substantially as described.
3. A flexible photographic film consisting of a flexible transparent or translucent

page_text: support composed of a nitro-cellulose compound containing a metallic salt soluble
in the nitro-cellulose solvents and a coating of sensitive emulsion substantially as
described.
4. A photographic film consisting of a "non-electric" support composed of a
nitro-cellulose compound containing an alkali nitrate and of a gelatino-argentic
emulsion substantially as described.
5. A photographic film consisting of a non-electric support composed of a
nitro-cellulose compound containing nitrate of ammonium and of a gelatino-argentic
emulsion substantially as described.
6. A photographic film consisting of a "non-electric" support composed in part
of a nitro-cellulose compound and a gelatino-argentic emulsion substantially as
described.
7. In the manufacture of sensitive photographic film involving the deposit upon a
foundation of a fluid or plastic substance which when set forms the support for the
sensitive emulsion and its subsequent stripping from the said foundation rendering
the emulsion support "non-electric whereby when the film is stripped from the
foundation electrical discharges are prevented substantially as described.
8. In the manufacture of sensitive photographic film involving the deposit upon a
foundation of a fluid or plastic substance which when set forms the support for the
sensitive emulsion and the subsequent removal of the complete film from the said
foundation rendering the emulsion support "non-electric" by the addition to it of
an alkali nitrate whereby when the film is stripped from the foundation electrical
discharges are prevented substantially as described.
9. In the manufacture of sensitive photographic film involving the deposit upon a
foundation of a fluid or plastic substance which when set forms the support for the
sensitive emulsion and the subsequent removal of the complete film from the said
foundation rendering the emulsion support "non-electric" by the addition to it of a
metallic salt whereby when the film is stripped from the foundation electrical
discharges are prevented substantially as described.
10. In the manufacture of sensitive photographic film involving the deposit upon a
support of a fluid nitro-cellulose compound which when dry forms the support for
the sensitive emulsion and the subsequent removal of the complete film from the
support, the improvement consisting in rendering the nitro-cellulose support "non-
electric" by the addition to it of a quantity of a metallic salt soluble in the nitro-
cellulose solvents and not precipitated by or precipitating the materials in the
compound whereby when the film is removed from the support electrical discharges
are prevented substantially as described.
11. In the manufacture of sensitive photographic film involving the deposit upon a
foundation of a fluid or plastic nitro-cellulose compound which when set forms
the support for the sensitive emulsion and the subsequent removal of the complete
film from the said foundation rendering the nitro-cellulose support "non-electric "
by the addition to it of nitrate of ammonium whereby when the film is removed
from the foundation electrical discharges are prevented substantially as described.
12. In the manufacture of sensitive photographic film involving the deposit upon a
foundation first of a gelatine solution secondly a nitro-cellulose compound and lastly
a sensitive gelatino-argentic emulsion the whole when dry being stripped from the
said foundation rendering the gelatine next to the foundation "non-electric" by the
addition to it of nitrate of potassium whereby when the film is removed from
the foundation electrical discharges are prevented substantially as described..
Dated this 20th day of January 1893.
W. P. THOMPSON & BOULT,
Agents for the Applicant.