Improvements in the Manufacture of Mineral and Enamel Colours for Use in the Production of Ceramic and other Photographs.
Year: 1895

page_text: Date of Application, 15th Feb., 1895
Complete Specification Left, 25th June, 1895-Accepted, 17th Aug.,
1895
PROVISIONAL DE MULTICATION.
Improvements in the Manufacture of Mineral and Enamel Colours
for Use in the Production of Ceramic and other Photographs.
I, GEORGE JONES ATKINS, of 1 Moselle Gardens, Tottenham, in the County of
Middlesex, Metallurgist, do hereby declare the nature of this invention to be as
follows:-
It is well known that attempts have been made to substitute mineral and enamel
colours for the carbon and other pigments used in the ordinary carbon process of
photography but hitherto, so far as I am aware, without success.
The carbon process consists broadly in the use of a compound of gelatine or
other analogous colloid, and carbon such as Indian ink for example, or other
pigment. This compound is spread upon paper and forms what is called carbon
tissue which is made sensitive to light by means of a solution of bichromate of
ammonium, sodium, or potassium, and when dry is placed under a suitable photo-
graphic negative and exposed to the action of light. This brings about a chemical
action by which the gelatine is rendered more or less insoluble, where the light has
passed through the negative, in proportion to the various gradations or half tones
of the negative. The gelatine, with the colouring matter mixed with it, is then
subjected to what is termed development that is to say the gelatine that has not
been locked down by the action of light and has therefore not been rendered
iusoluble, is washed out with hot water.
The mineral and enamel colours generally consist of the oxides of the metals in
combination with silica and alkaline earths and metals. When substituting these
colours for carbon it has been found, on sensitizing the tissue and drying it, that
there has already been brought about in the whole film a similar chemical action to
that produced by light, locking the film down and rendering it quite insoluble
through the action of the sensitizing salts upon the compound of gelatine and the
mineral colouring matter. This effect takes place without the action of light,
and renders the tissue or compound quite valueless and unfit for photographic
purposes.
The effect above referred to seems to be caused by the combination of chromium
salts with the metals, thereby eliminating the oxygen.
The colours most acted upon in this way are the oxides of iron, manganese,
copper and cobalt, and these are the principal ingredients employed in producing
the various dark coloured pigments used in the vitrifiable colours and are of the
greatest commercial value.
The object of the present invention is to obviate the above described premature
action of the sensitizing salt upon the compound of gelatine and mineral colouring
matter; and for this purpose I combine the chromium salts with the mineral or
enamel colour in such manner as to bring about the combination, and the consequent
chemical change before the compound is brought into contact with the gelatine or
other colloid substance.
This combination and consequent change may be effected in a variety of ways,
for example, according to one method I grind the mineral or enamel colour to a
powder and then treat it with a solution of chromic acid or bichromate of
ammonium, potassium or sodium of a sufficient strength to satisfy the metals or
minerals in the colour under treatment. This satisfaction of the metals or
minerals with chromium salts can always be secured by having a slight excess of
Γ

page_text: the chromium salt, which excess is' indicated by its imparting a yellow tint to the
solution. The resulting compound is then dried or not, according to circumstances
and may be mixed with the gelatine or other colloid, and made into tissue or film
without fear of any premature action taking place when treated with the sensitizing
medium.
In the case of the enamel colours the combination of the satisfying chromium
salt with the metallic oxide may be effected in the crucible in which the fluxes and
minerals are fused together, but the colours are generally somewhat changed by
that method of treatment.
The salt of chromium may be combined with the mineral or enamel colour in the
grinding operation. Furthermore if the colour is to be used immediately after
preparation, the chromium salt may be added at once in sufficient excess to
sensitize the compound of colour and gelatine or other colloid forming the tissue
or film.
I prefer the humid method of treatment first above described, as the excess of
chromium salt can be readily washed out, and the colour can be used in the wet
state, or dried and kept for subsequent use.
ROC DE May on coruary 1000.
· G. J. ATKINS,
Per W. H. Beck,
115 Cannon Street, London, E.C., Agent.
Improvements in the Manufacture of Mineral and Enamel Colours
for Use in the Production of Ceramic and other Photographs.
I, GEORGE JONES ATKINS, of 1 Moselle Gardens, Tottenham, in the County
of Middlesex, Metallurgist, 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:-
It is well known that attempts have been made to substitute mineral and enamel
colours for the carbon and other pigments used in the ordinary carbon process of
photography but hitherto, so far as I am aware, without success.
The carbon process is based upon the use of a mixture of gelatine or other
analogous colloid used as vehicle and carbon, such as Indian ink for example, or
other pigment. This mixture is spread upon paper and forms what is called
carbon tissue which is made photo-sensitive by means of a solution of bichromate
of ammonium, sodium, or potassium, and when dry is placed under a suitable
photographic negative and exposed to the action of light. This brings about a
chemical action by which the gelatine is rendered more or less insoluble, where
the light has passed through the negative. "The tissue after suitable exposure is
then transferred and subjected to the well known process of development, that
is to say, the gelatine that has not been rendered insoluble by the action of
light is washed out with hot water.
When ceramic or vitrifiable pigments are substituted for carbon it is found that
on sensitizing the tissue and drying it, there has already been brought about a
similar chemical action to that produced by light, which renders the tissue or
compound unfit for photographic purposes.
Of the metallic compounds constituting these pigments those which are most
acted upon in this way are the oxides of iron, manganese, copper, lead and cobalt,
and these are the principal ingredients employed in producing the various dark
coloured pigments used for vitrifiable colours and are of the greatest commercial
value.

page_text: The object of the present invention is to obviate the above described premature
action of the mineral pigments upon the mixture of gelatine and sensitizing salt.
For this purpose I treat the mineral or enamel colour preferably with solutions of
soluble chromate in such manner as to bring about saturation of the constituents
of the enamel mixture with chromic oxide (Cr O³) thus preventing the reaction
above described when the compound is brought into contact with the gelatine or
other colloid substance in admixture with the sensitizing salt.
This combination and consequent change may be effected in a variety of ways,
for example, according to one method, I grind the mineral or enamel colour to a
powder and then treat it with a solution of chromic acid or bichromate of
ammonium, potassium or sodium of a sufficient strength to satisfy the metals or
minerals in the colour under treatment. This satisfaction of the metals or minerals
with chromium oxide can always be secured by having a slight excess of the
chromium salt which excess is indicated by a yellow tint imparted to the solution.
The resulting compound is then dried or not according to circumstances and may
be mixed with the gelatine or other colloid, and made into tissue or film without
fear of any premature action taking place when it is afterwards treated with the
sensitizing agent.
In the case of the enamel colours the preliminary combination of the chromium
salt with the metallic oxide may be effected in the crucible in which the fluxes and
minerals are fused together but the colours are generally somewhat changed by
this method of treatment.
The salt of chromium may also be combined with the mineral or enamel colour
in the grinding operation.
I prefer the humid method of treatment first described above, as the excess of
chromium salt can be readily washed out, and the colour cau be used in the wet
state, or dried and kept for subsequent use.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:
The herein described method of rendering mineral and enamel colours suitable
for photography by treating them with chromic compounds sufficient to saturate
their metallic components before mixing them with the gelatine or other colloid
substance for forming films.
Dated this 90th day of May 1895
Dated this 90th day of May 1895
G. J. ATKINS,
Per W. H. Beck,
115 Cannon Street, London, E.C., Agent.