Method of Producing Glass Etching Plates for Use in Reproducing Designs on Stone, Zinc, Copper, Brass, and the like.
Year: 1896

page_text: Date of Application, 9th May, 1396
Complete Specification Left, 8th Feb., 1897-Accepted, 8th May, 1807
Method of Producing Glass Etching Plates for Use in Reproducing
Designs on Stone, Zinc, Copper, Brass, and the like.
I, THEODOR LÖHLER, of Mannheim, T. 6. 36, in the Grand-Duchy of Baden,
in the Empire of Germany, Manufacturer, do hereby declare the nature of this
invention to be as follows:-
As is well known, the preparation from wood of plates for sub-surface printing
is generally attended with considerable difficulty for the printer, owing to the
variations in the hardness of the wood glued together. Where the wood is soft.
the chisel sinks deeper than would be the case with harder wood, with the result
that quite another tone comes out in the printing. It is true an effort has been
made to avoid this evil by coating the zinc, brass or copper plate with asphalt and
then deeply corroding it. Plates prepared in this way, are doubtless very excellent
when the object in view is the production of a pattern or design, but directly
one attempts to introduce lettering and ornamentation difficulties are experienced,
while it is only possible to produce such plates in the negative.
In order to obtain a good and clean copy for sub-surface printing it was necessary
to first engrave it in stone or copper. The positive plate could then be taken for
printing purposes from the engraved plate. The multiplication of the engraving
however proved a task of such difficulty that it could only be instructed to the
most skilled workmen. Hence the very high price which was demanded.
It is claimed for the method of procedure here described that it at once removes
all these difficulties. The method relates to the production of glass etching plates
for copying upon stone, zinc, copper, brass and such like.
The essential feature of the process is the production of a white layer or coating
upon glass by means of various chemicals. After the etching has been completed
an intense blacking is given to the coating by means of dry steam.
The process is essentially as follows:-
A preparation of collodium and iodine specially made for this purpose, is first
poured on to a glass plate. The plate provided with this coating is then placed in
a vessel containing a solution of 1 part nitrate of silver to 15 to 20 parts water, to
which is added a small quantity of nitric acid (8 to 12 drops for each litre of
aqueous silver solution) and exposed to the action of the light. Afterwards the
plate is placed in a second vessel containing an aqueous solution of green vitriol
with a slight quantity of sulphuric acid and spirits. There it remains a short time
and after being well rinsed and the back carefully cleaned with proto chloride of
silver, it is found to have a greyish-brown color, but a color varying from dark
brown to almost black, when held up to the light. The plate is then placed in a
third vessel filled with a solution of mercury sublimate saturated in water and
remains until it has a white appearance. Held up to the light, the layer is then
but non-transparent. Albumen or gum arabic is next poured on the plate, in order to
obtain a very fine effect in the etching, the proportion being 20 grams fluid albumen
When the
to 100 grams water or 8 to 12 grams gum arabic to 100 grams water.
plate is dry its condition is extremely fine, although it still offers too much
resistance to allow of perfectly free work being done upon it. Of course, such
agents as thin negative varnish can be used instead of albumen or gum arabic.

page_text: The plate is now so far prepared that it can be handed over to the artist. The
drawing is made on the plate to the right. Should it be necessary to make a
preliminary sketch, a piece of paper can be used for the purpose and afterwards
fastened on the edge with gum, wax or similar material. The lines of the sketch
are then traced with a pencil or other instrument, at the same time any corrections
being made that may be necessary. A slight pressure is sufficient in order to
transfer the sketch sharply and clearly on to the etching plate without it being
necessary to cover the back of the thick or thin sketch sheet with graphite or
reddle. After the work of transference has been completed, the drawing is
removed and the etching is made with an English point, scraper, graver etc.
Should the drawing not turn out. as desired, the defects can be avoided during the
process of etching, as the lines traced have little or no effect in the subsequent
reproduction. Where the etching has been made from drawings upon which the
lines are equal, i.e., where a certain tone is present, the free hand style of drawing
is followed, the plate is mounted upon a block, and the straight or wavy lines are
worked out with an engraving machine. By this method, it is possible to etch
views etc. upon fine letter-heads, cheques, etc.
From the above it will be seen that by this method, the etching is made from
the right side only. This shows a great advantage over other methods, adopted
hitherto, an artist never being able to give scope to his talent when compelled to
work from the left. The method is admirably adapted for preparing stenographis
work, maps, hand writing etc. By means of the glass etching process it is possible
to make a perfect and exact copy of an artistic creation.
The etched glass plate however not being ready for reproduction upon stone,
zinc etc.; it must undergo a further treatment. The white, more or less non-
transparent plate is therefore exposed to the action of the dry vapors of volatile
chemicals. For instance, a piece of felt or similar substance evenly saturated with
spirit of sal ammoniac is placed at the bottom of a tightly closed box and the plate
laid over it. As soon as the box has been closed, the coating of the plate receives
a perfectly black stain, while the etching remains as clear as glass. Thus the
drawing, which has a glass-like clearness, is surrounded by a dark and thoroughly
non-transparent layer, rendering the work of re-production quicker and more
certain than was hitherto the case.
It is possible to copy several degrees beyond what the photometer shows without
interrupting the continuous work in any way. Further the process of development
proceeds very quickly, whether the copying is done with asphalt, albumen, gum,
enamel, or on the American resin system.
It is very evident that by means of such a method, etching plates can be
previously prepared for reproduction on stone, zinc, copper, brass etc. in the
quickest mauner possible, and drawings made upon them with a delicacy and
faultlessness such as cannot be equalled by a pen and ink artist on paper.
It must be here added that a pen and ink sketch must at first be made larger,
and then be reduced in the process of photography. That was the only resource
in order to produce a cliché from line drawings. Several conditions were necessary
to ensure a faultless piece of work, which, however, was never so perfect as with
the glass etching process. In preparing a pen drawing, the photographer has to
produce a negative. The drawing often showed gray lines' and points, but in the
negative they became dim and in the subsequent reproduction process, obliterated,
so that much time was lost in making repeated reproductions. None of these
difficulties are met with in the new process. The drawing is made on the correct
scale and does not need photographing. It is only copied, but the copy is done
with certainty and accurateness. Further, the glass plates, which are previously
blacked, retain their black stain only as long as they remain in contact with the
plates to be copied. Soon after the latter are removed they regain their white
color. Consequently the glass plate, which in the case of large drawings, bas
many free spots, can be used for small etchings. These last named can then be
always produced on a white ground.

page_text: The glass etchings can be retouched without any trouble whatever. It is only
necessary to paint the parts in question with Chinese white and make the corrections
when dry. After the blacking, Siberian graphite is rubbed into the spots, which
thereupon become black. Neither the glass nor the adjoining drawing take
graphite. The etched glass plates can be used equally well for chromo printing,
as for illustrations, the production of sub-ground plates (designs for paper money.)
heliography, heliogravure, e'c. by the simple process of copying. They can be
enlarged as desired by photography without losing any of their sharpness.
Mannheim, 9th May 1896.
THEODOR LOHLER.
Method of Producing Glass Etching Plates for Use in Reproducing
Designs on Stone, Zinc, Copper, Brass, and the like.
I, THEODOR LÖHLER, of T. 6. 36, Mannheim, in the Grand-Duchy of Baden,
Empire of Germany, Manufacturer, 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:-
inting
the
ioft,
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As is well known the preparation from wood of plates for sub-surface
is generally attended with considerable difficulty for the printer, owin,
variations in the hardness of the wood glued together. Where the wood
the chisel sinks deeper than would be the case with harder wood, with the
that quite another tone comes out in the printing. It is true an effort has
made to avoid this evil by coating the zinc, brass or copper plate with asphalt
then deeply corroding it. Plates prepared in this way, are doubtless
excellent when the object in view is the production of a pattern or desig
directly one attempts to introduce lettering and ornamentation difficulti are
experienced, while it is only possible to produce such plates in the negative.
In order to obtain a good and clean copy for sub-surface printing it was necessary
to first engrave it in stone or copper. The positive plate could then be taken for
printing purposes from the engraved plate. The multiplication of the engraving
however proved a task of such difficulty that it could only be intrusted to the most
skilled workmen. Hence the very high price which was demanded.
It is claimed for the method of procedure here described that it at once removes
all these difficulties. The method relates to the production of glass etching plates
for copying upon stone, zinc, copper, brass and such like.
The essential feature of the process is the production of a white layer or coating
upon glass by means of various chemicals. After the etching has been completed
an intense blacking is given to the coating by means of dry steam.
The process is essentially as follows:
A preparation of collodion and iodine specially made for this purpose and
consisting of 2 parts of collodion, 135 parts of alcohol, 115 parts of ether, 3,5 parts
of iodide of cadmium, 1 part of bromide of cadmium and 3 parts of iodide of
ammonium, is first poured on to a glass plate. The plate provided with this
coating is then placed in a vessel containing a solution of 1 part nitrate of silver
to 15 to 20 parts water, to which is added a small quantity of nitric acid (8 to 12 drops
for each litre of aqueous silver solution) and exposed to the action of the light.
Afterwards the plate is placed in a second vessel containing an aqueous solution
of green vitriol with a slight quantity of sulphuric acid and alcohol. There it
remains a short time and after being well rinsed and the back carefully cleaned with
proto chloride of silver, it is found to have a greyish-brown color, but a color

page_text: varying from dark brown to almost black, when held up to the light. The plate is
then placed in a third vessel filled with a solution of mercury sublimate saturated
in water and remains until it has a white appearance. Held up to the light, the
layer is then but non-transparent. Albumen or gum arabic is next poured on the
plate, in order to attain a very fine effect in the etching, the proportion being
20 grams fluid albumen to 100 grams water or 8 to 12 grams gum arabic to
100 grams water. When the plate is dry its condition is extremely fine, although
it still offers too much resistance to allow of perfectly free work being done upon
it. Of course such agents as thin negative varnish can be used instead of albumen
or gum arabic. The plate is now so far prepared that it can be handed over to
the artist. The drawing is made on the plate to the right. Should it be necessary
to make a preliminary sketch, a piece of paper can be used for the purpose and
afterwards fastened on the edge with gum, wax or similar material. The lines of
the sketch are then traced with a pencil or other instrument, at the same time
any corrections being made that may be necessary. A slight pressure is sufficient
in order to transfer the sketch sharply and clearly on to the etching plate without
it being necessary to cover the back of the thick or thin sketch sheet with graphite
or reddle. After the work of transference has been completed, the drawing is
removed and the etching is made with an English point, scraper, graver etc.
Should the drawing not turn out as desired, the defects cau be avoided during the
process of etching, as the lines traced have little or no effect in the subsequent
reproduction. Where the etching has been made from drawings upon which the
lines are equal, i.e., where a certain tone is present, the free hand style of drawing is
followed, the plate is mounted upon a block, and the straight or wavy lines are
worked out with an engraving machine. By this method, it is possible to etch
views etc. upon fine letter-heads, cheques, etc.
From the above it will be seen that by this method, the etching is made from
the right side only. This shows a great advantage over other methods, adopted
hitherto, an artist never being able to give scope to his talent when compelled to
work from the left. The method is admirably adapted for preparing stenographic
work, maps, hand writing etc. By means of the glass etching process it is possible
to make a perfect and exact copy of an artistic creation.
The etched glass plate however not being ready for reproduction upon stone,
zinc etc., it must undergo a further treatment. The white, more or less non-
transparent plate is therefore exposed to the action of the dry vapors of volatile
chemicals. For instance, a piece of felt or similar substance evenly saturated with
spirit of sal ammoniae is placed at the bottom of a tightly closed box and the plate
laid over it. As soon as the box bas been closed, the coating of the plate receives
a perfectly black stain, while the etching remains as clear as glass. Thus the
drawing, which has a glass-like clearness, is surrounded by a dark and thoroughly
non-transparent layer, rendering the work of reproduction quicker and more certain
than was hitherto the case.
It is possible to copy several degrees beyond what the photometer shows without
interrupting the continuous work of copying in any way. Further the process of
development proceeds very quickly, whether the copying is done with asphalt,
albumen, gum, enamel, or on the American resin system.
It is very evident that by means of such a method, etching plates can be previously
prepared for reproduction on stone, zinc, copper, brass etc. in the quickest manner
possible, and drawings made upon them with a delicacy and faultlessness such as
cannot be equalled by a pen and ink artist on paper.
It must be here added that a pen and ink sketch must at first be made larger, and
then be reduced in the process of photography. That was the only resource in
order to produce a cliché from line drawings. Several conditions were necessary
to ensure a faultless piece of work, which, however, was never so perfect as with
the glass etching process. In preparing a peu drawing, the photographer has to
produce a negative. The drawing, often showed gray lines and points, but in the
negative they became dim and in the subsequent reproduction process, obliterated,

page_text: so that much time was lost in making repeated reproductions. None of these
difficulties are met with in the new process. The drawing is made on the correct
scale and does not need photographing. It is only copied, but the copy is done
with certainty and accurateness. Further, the glass plates, which are previously
blacked, retain their black stain only as long as they remain in contact with the
plates to be copied. Soon after the latter are removed they regain their white
color. Consequently the glass plate, which in the case of large drawings, has many
free spots, can be used for small etchings. These last named can then be always
produced on a white ground.
The glass etchings can be retouched without any trouble whatever. It is only
necessary to paint the parts in question with Chinese white and make the corrections
when dry. After the blacking, Siberian graphite is rubbed into the spots which
thereupon become black. Neither the glass nor the adjoining drawing take graphite.
The etched glass plates can be used equally well for chromo printing, as for illustrations,
the production of sub-ground plates (designs for paper money,) heliography, helio-
gravure, etc. by the simple process of copying. They can be enlarged as desired by
photography without losing any of their sharpness.
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 :-
1. Method for producing a non-transparent, white coating upon glass plates for
etching, in which the plate is first covered with a layer of collodion and iodine
consisting of 2 parts of collodion, 135 parts of alcohol, 115 parts of. ether, 3,5 parts
of iodide of cadmium, 1 part of bromide of cadmium and 3 parts of iodide of
ammonium, then treated with a solution of nitrate of silver, next with an aqueous
solution of green vitriol containing sulphuric acid and alcohol, and finally with a
solution of mercury and albumen.
2. After the process of etching the treatment of the white coating, produced as
shown under Claim 1, on glass plates, with the dry vapors of volatile chemicals,
for the purpose of rendering it possible to use the plates for reproduction upon
other objects, and at the same time, of giving them once more a white color for
further etching.
Dated this 4th day of February 1897.
MAX WERTHEIM,
Agent for Applicant.