Glass, or other Material for the Production of Copies of Drawings, Designs, Pictures, Photographs, Writings, and the like by the Action of Light.
Year: 1887

page_text: Date of Application, 6th Aug., 1887
Complete Left, 7th May, 1888
Complete Accepted, 8th June, 1888
Glass, or other Material for the Production of Copies of Drawings,
Designs, Pictures, Photographs, Writings, and the like by the
Action of Light.
I HENRY JOSEPH SHAWCROSS of the Water Engineers Office, Dale Street, Liver-
pool, in the County of Lancaster, Bachelor in Engineering do hereby declare the
nature of my said invention to be as follows:-
This Invention has for its object the obtaining by the action of light exact copies of
Drawings Designs Pictures, Photographs, Writings and the like, drawn, written,
printed, or impressed in monochrome, or vari-coloured lines, or shadow on a trans-
lucent medium; in an ink black, or sometimes coloured positive picture on a white,
or coloured ground.
My Invention is founded upon the fact that a ferric salt when mixed with an organic
acid and other organic substance, such as gelatin and allowed to dry in a thin film
in the dark and then exposed to the action of light is reduced to the ferrous state
according to the degree and intensity of the light and in this latter condition will be
more, or loss incapable of forming mordants for certain dye stuffs, such as Gallic, or
Tannic Acid, Catechu, Sulphocyanide, or Ferrocyanide of Potash and the like, although
previous to exposure the film would have been stained to an ink black, green, red, or
blue by an application of a solution of these respective chemicals.
According to my Invention I cover the surface of paper, woven fabrics, tissue,
glass, porcelain, metal, wood, or other material on which the copy is to be produced,
with a chemical composition consisting of
A ferric salt namely the double sulphate of iron and aluminium, known as "iron
alum."
An organic acid such as Citric or Tartaric acids.
An organic matter such as Gum Dextrine, Gelatin, or Glucose.
This I spread either by hand, or mechanical means in a thin film evenly over the
surface it is desired to coat. It is then allowed to dry in a subdued, or nou actinic

page_text: light, or in the dark. It is now ready for use and will keep in good condition and
remain sensitive to light over a lengthened period. By exposing any medium so
prepared to the action of light beneath and in close contact with a Drawing to be
copied so as to chemically alter the condition of those parts not covered by the
dark, or coloured lines, or half tones of the original and subsequently immersing the
same in a solution of Tannic Acid or other Dyestuff capable of forming a coloured
precipitate with the Ferric Salt but not with the reduced or ferrous salt, those parts
which have been covered and thus unaffected by the light are dyed through a com-
bination of the two chemical substances to an ink black, or other colour.
To remove false marks such as ink stains I employ a weak acid solution having a
stronger affinity for iron than the Tannic Acid or other Dyestuff.
Dated this Fifth day of August 1887.
The Preparation and Treatment of Paper, Woven or Tissue Fabrics,
Glass, or other Material for the Production of Copies of Drawings,
Designs, Pictures, Photographs, Writings, and the like by the
Action of Light.
I HENRY JOSEPH SHAWOROSS of the Water Engineers Office Dale Street Liverpool
in the County of Lancaster Bachelor in Engineering, do hereby declare the nature of
my said invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :-
This invention has for its object the obtaining by the action of light exact-copies
of Drawings, Designs, Pictures, Writings, and the like, drawn, written, printed or
impressed in monochrome or vari-coloured lines, or shadow on a translucent medium,
in an ink black, or sometimes coloured picture on a white or coloured ground.
I have discovered and my invention is based upon the fact that a ferric salt when
mixed with an organic acid and other organic substance, such as Gelatin and allowed
to dry in a thin film in the dark forms, previously to the action of light upon it, a
perfectly insoluble film. But after it is exposed to the action of light those parts of
the filni acted upon become reduced to the ferous state, and are, in that condition,
easily soluble. In this latter condition it will be more or less incapable of forming
mordants for certain dye-stuffs, such as Gallic or Tannic Acid, Catechu, Sulphocyanide

page_text: or Ferrocyanide of Potash, and the like, although previous to exposure the film would
have been stained to an ink black, green, red, or blue by an application of a solution
of these respective chemicals.
According to my invention I cover the surface of paper, woven fabrics, tissue, glass,
porcelain, metal, wood, or other material on which the copy is to be produced, with
a chemical composition consisting of:-
-:
A ferric salt, namely the double sulphate of iron and aluminium known as “iron
alum."
An organic acid such as Citric or Tartaric acids.
An organic matter such as Gum, Dextrine, Gelatin, or Glucose.
In actual practice I have found the proportions of chemicals used in the composition
above set forth to vary somewhat with the nature of the substratum used, and the
thickness of the film applied. Upon paper I have obtained the best results in ink
black on a white ground with about the following parts by weight-namely—
with advantage.
The solution having been prepared hot is spread over the surface of the paper or
other material to be coated. It is then hung up or otherwise suitably supported in
the dark, or in a subdued or non-actinic light to dry. After drying it will be
ready for use and may be stored or put away. It will remain in good working
condition over a lengthened period.
If
If it is desirable to diminish the proportion of Gelatin of the solution the
Tartaric or other acid must be proportionately increased to as much as twofold.
the solution be applied in a very thin film it is well to increase the proportion of
Gelatin to as much as threefold, and the iron alum may be increased as much as
50 per cent. I have obtained the best results within these limits on paper. But with
different materials, the proportions may even exceed those given.
When dry the combination of the Iron Alum with the Gelatin and Tartaric Acid
will, previous to the action of light, form a perfectly insoluble film, but after exposure
thereto those parts acted upon become reduced to the ferous state, and the film becomes
easily soluble.
By exposing any medium such as paper prepared with the above chemical com-
position to the action of light, beneatli and in close contact with a Drawing, to be
copied, the parts exposed to and acted upon by the light become reduced to the ferous
state and are soluble, and the parts covered by the lines of the Drawing remain
insoluble.
On treatment now with Tannic acid or similar compounds such as Gallic Acid or
Catechu the ferric combination will be stained to an ink black, or a green respectively
more or less all over the surface. Or this same end, namely, the attainment of any
desired colour may be effected by the addition to the composition used for the film
of any coloured pigment or colouring matter as described. If the film on the
material used be the plain uncoloured composition, and be treated with Ferrocyanide
of Potash, it will be changed to Blue, or with Sulphocyanide of Potash to a
red, and so on; but to obtain photo copies in Prussian Blue it will be necessary
to reduce the quantity of Tartaric Acid in the sensitive solution to 40 per cent. or
less of the quantity named.
Or in lieu of developing with a solution of the chemical reagents herein described
I may rub in and thoroughly embody into the surface of the dry sensitive film the
same chemical reagents in the form of a fine or inpalpable powder, either before, or

page_text: after exposure to light. The final step of development in this case will be effected
simply by immersing the exposed print in a simple solvent such as water.
On immersing the material so treated after exposure in water or other solvent, such
as weak acid solutions, it will be found that those portions rendered soluble by the
action of light will come freely away, leaving the ground of the paper or other material
exposed, clean and free from colour, whilst those parts on which the light has not
acted will be stained to the colour induced by the dyetsuff used, or effected by the
colouring matter used.
When a coloured pigment is used with the chemical composition-for example
light Indian ink, Indigo, the aniline colours, and other like pigments-it is mixed
with the composition, and the film coated upon the material will present a coloured
surface. When the paper or other fabric coated with this coloured composition is
exposed with the Drawing to be copied to the action of light, it renders the exposed
parts soluble, and so that they can be removed by immersion in a solvent such as
water. The soluble parts will dissolve freely away carrying with them the coloured
pigmental matter, and leaving more or less exposed the white or coloured surface
of the paper, and the lines of the Drawing, according as the light has been strong or
weak or more or less prolonged. Or, the surface of the chemical film may be covered
with Printers, Lithographers, or other equivalent inks, or colouring matters, in which
case the soluble parts can be dissolved freely away carrying with them the inked or
coloured surface or ground, and leaving the lines of the Drawing. When using inks
or pigments in this way, if they are of a light colour they may be applied to the
surface of the film before or after exposure, and before developing; but if they are of
a dark colour or black they must be applied atter exposure and before developing.
For producing copies of Drawings, Designs, Pictures, Photographs, Writings, and
the like by the action of light, the prepared paper is exposed at the back of a
transparency in a photo frame in the usual way to the brightest light available,
preferably sunshine. If the film has been applied without pigment or colouring
matter the ground will be observed to change to a light hue, leaving a copy of the
drawing in yellow lines on a light coloured ground. After sufficient exposure the
copy may be developed. If the sensitive solution has had a pigment mixed with it
before exposure, or if the pigment has been applied to the surface after exposure,
then all that is necessary is to soak the copy in a bath of water, weak acid or other
solvent; the removal of the piginental Gelatin in the soluble or exposed parts being
aided by rubbing with a soft brush.
To obtain ink black copies without pigment, a suitable developing solution may be
made by mixing 3. oz. of Tannic Acid with 60. oz. of cold water. The solution
will soon clear and be ready for use. It may be applied by floating over the surface
of the exposed print when the lines or overshadowed portions of the surface will
immediately turn to an ink black, and a dirty scum will cover the surface. This
scum may be removed by immersion in a bath of water, the surface being rubbed all
over with a brush or sponge when it will be found to come freely away. If the
exposure has been sufficient, the print will now show up in black lines or tones on a
white ground. To ensure permanent whiteness and the removal of all chemical
matter, the copy should be immersed in one or two relays of clean water. It may
then be dried before the fire, hung up.or blotted, and will be complete.
To obtain copies in Prussian Blue without pigment, I use as a developer a more or
less saturated solution of Ferrocyanide of Potash, and proceed as in the last process.
The exposure required for this developer will be found to be much less than that for the
ink process above described. When the picture stands out sufficiently boldly in blue
on a light coloured ground, the development is stopped by washing away the Ferro-
cyanide of Potash in water. The copy is then immersed in a weak acid solution,
when the exposed portions will dissolve, and may be washed freely away. When dry
the copy will be complete.
In the foregoing specification I have described what I have found the best form
in which Iron and Aluminium may be used in the preparation and treatment of
materials such as are herein described, for producing copies of Drawings, Designs

page_text: Pictures, Photographs, Writings, and the like by the action of light, involving my
invention. I wish it to be understood however, that I do not confine or restrict
myself to the particular state, form or combination in which the Iron and Aluminium
are introduced and used in the carrying out of the invention, for under modified and
suitable conditions the said metals may be made available for the purpose in other
forms, states or combinations without departing from the spirit or nature of my
invention, so long as they take their part in the chemical reactions and mutual
decompositions which take place in the carrying out of or use of the invention, in the
manner, or substantially in the manner herein set forth.
Having now particularly described and ascertained the nature of my said
Invention and in what manner the same is to be performed I declare that what 1
claim is --
1. In the preparation and treatment of Paper, Woven or Tissue Fabrics, Glass, or
other material for the production of copies of Drawings, Designs, Pictures, Photo-
graphs, Writings, and the like, by the action of light, as herein described, the use of
Iron and Aluminium, either in the form or state of the Ferric salt known as Iron
Alum, or in any other equivalent form or forms.
2. Material of the kinds herein described provided with a thin sensitive film
substantially as herein described.
3. In the preparation and treatment of materials of the kinds herein described, for
the production of copies of Drawings, Designs, Pictures, Photographs, Writings, and
the like, the use in combination of Iron Alum, an organic acid, and organic matter,
substantially as herein set forth.
4. In the preparation and treatment of materials of the kinds herein described for
the production of copies of Drawings, Designs, Pictures, Photographs, Writings, and
the like, the use in combination of Iron Alum, an organic acid, an organic matter
and a pigment or colouring matter, substantially as herein set forth.
5. In the treatment of materials of the kinds herein described for the production of
copies of Drawings, Designs, Pictures, Photographs, Writings, and the like in which
the film or coating of the material is made as described, obtaining black or coloured
prints by providing the surface of the film with a black or coloured ink, or other
equivalent colouring substance, prior to the developing or washing of it, substantially
as herein set forth.