Process for Simultaneously Developing and Fixing a Latent Photographic Image.
Year: 1899

page_text: Date of Application, 4th Mar., 1899-Accepted, 22nd Apr., 1899
COMPLETE SPECIFICATION.
Process for Simultaneously Developing and Fixing a Latent
Photographic Image.
I, LUDWIG ELLON, of 33, Helmholtzstrasse, in Charlottenburg, near Berlin,
Germany, Doctor of Philosophy and Chemist, 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 usual photographic process has hitherto been considered defective in that
the image produced in the developing is not at the same time rendered permanent
but only acquires that quality by the subsequent fixing operation. Endeavours
have therefore long been made to simplify the photographic process by uniting the
developing and the fixing operations into one.
The various attempts in this direction have in some special cases led to interesting
results but not as yet to a really generally applicable practical process.
Of recent labours in this direction I may mention those of Punnett who on
page 126 of the British Journal of Photography for 1898 describes the obtaining of
a fixed image with some kinds of diapositive or lantern plates, (gelatine plates,
containing chloride and bromide of silver) by the application of a strongly caustic
alkaline ortol developer in the presence of a fixing salt.
But with the best diapositive plates in the market and strictly following Punnett's
directions I obtained an image of only very small intensity. And the bromide of
silver-gelatine-dry plates used for producing negatives and therefore much more
important gave no image at all when used according to Punnett's process.
W. B. Bolton describes on page 804 of the British Journal of Photography for
1898 and on pages 20 and 52 of the same Journal for 1899 a developing,
strengthening and fixing in one operation (not however for simplifying the process
but for obtaining perfect negatives), but he denies from his own experiments the
possibility of applying successfully the process to bromide of silver dry plates.
It is also known that hyposulphite of soda easily dissolves bromide of silver
exposed to light, and none of the heretofore used developer solutions including the
so-called rapid developers have been able to surpass in effect the said hypoзulphite,
or to yield a useful image by the presence of hyposulphite in excess. The
pyrocatechine in the form heretofore used forms no exception in this
application.
It is further known that slowly acting alkaline developers can be to some
extent rendered into rapid developers by substituting caustic alkalies for the
carbonates. But while for instance with the isomeric hydrochinone three to four parts
of hydrate of potash are required for one part of hydrochinone in order to produce a
rapid developer (which owing to its strongly alkaline character has only a limited
application) pyrocatechine on the other hand (and this is new), with the amount of
alkali hydrate required for formning the di-alkali-salt, or with a still smaller amount

page_text: For a ury place to by to c. 1s used.
II
{
10 cubic cm. on the concentrated developer 1.
20
20
"
>>
soda fixing solution 1 to 5.
water.
"
"
Without prolonging the time of exposure beyond the usual, one obtains by
instantaneous or by time exposure in the course of three to five minutes (all according
to the kind of plate used) a perfect, well graduated nicely covered and perfectly fixed
negative.
An unexpected advantage of the process shews itself here at once, in that the
whole process is completed in a fraction of the time, heretofore considered necessary
for a successful process.
The used developer may be used for a second and third plate.
The fixing developer equalizes various degrees of exposure so that even a much
over-exposed plate when treated with a freshly formed developer yields a negative
that can be copied. Like the ordinary developer it may easily adapt itself to
various cases by dilution, by applying used developer or by suitable additions such
for instance as bromide of potash and the like. The fixing developer may thus
also be successfully used for films, bromide of silver paper or lantern plates. Very
remarkable results are obtained with the latter while using a developer composed
for instance as follows:-
A perfectly clear and good image is thus obtained in the shortest possible
time.
Instead of the hydrate of potash I may with quite similar success eniploy hydrate
of soda or of lithium or a mixture of two or three of these bases and I may also let
other subsulphurous alkali salts partly or wholly take the place of the subsulphurous
soda (hyposulphite).
The aforesaid relative amount of alkali in the developer is only chosen as an
example; it may be varied within rather wide limits without rendering the success
of the process quite doubtful.
The technical value of the described new process would thus not only depend
upon that it at once solves the old problem by the developing to obtain enduring
photographic images in a surprisingly simple and yet complete inanner thus affecting
a material saving to the amateur and the professional photographer in time, labour
and tools, but also on the circumstance that it gives results so distinctly good as
not to be attained so easily and certainly by the heretofore usual process.
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 :-
A process for simultaneously developing and fixing latent photographic images
consisting in treating the exposed photographic gelatine plates, films or papers

page_text: with a solution containing an alkali compound or alkaline compounds of
pyrocatechine and a fixing agent, especially a subsulphurous salt or subsulphurous
salts.
Dated this Fourth day of March 1890
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.