A NEW OR IMPROVED PROCESS OF ETCHING
Year: 1884

page_text: I, HERBERT JOHN HADDAN, of the firm of Herbert and Company, Patent Agents,
of 67, Strand, in the City of Westminster, Civil Engineer, do hereby declare the
nature of my Invention for A NEW OR IMPROVED PROCESS OF ETCHING, and
in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:-
This Invention relates to a new or improved process of etching for the production
of wood-imitations of all kind upon endless paper or any other suitable material
and for other purposes.
a.) For this purpose I prepare first an original matrice-die of a plate of zinc,
both faces of which are cleaned by means of water and which is then uniformly
covered with an etching ground of isolit.
b.) Upon the plate thus prepared the design of the speckle to be produced is
drawn or engraved by means of a graver. Those parts of the drawing which are
to be reprinted I leave covered by the etching ground whilst the other parts are
freed from the etching ground by means of a suitable tool.
c.) After this operation the plate is placed in a low wooden tub, that has been
caulked with pitch and water is poured over the plate, thus cleaning the plate of
the particles of isolit and of any dust and impurities. The employ of rain water is
the most preferable and if that is not to be obtained the use of well boiled soft
water is to be recommended. The vessel above mentioned is generally filled to
such a height, that the plate (the upper face of which is the one partly covered by
isolit) is just covered by the water.
After this the plate is ready for etching.
d.) I now add a little pure non fuming nitric acid (HNO, + aqua).
The quantity of the acid to be added in this initial stage of the operation
amounts to 15% of the quantity of water employed.
The bubbles of gas which soon commence to develop are constantly removed
from the surface of the plate by means of a coarse brush in order to secure a
uniform etching of the plate.
Owing to the careful removal of the gas the drawing obtained by the etching
process is sharp and distinct without containing any protuberances (raised portions)
C

page_text: or cavities in the etched parts, which otherwise would be produced by a not
sufficiently uniform action of the acid and further the corrosion of the plate under
the isolit is prevented.
Generally I do not etch any deeper than one millimeter below the surface of the
zinc-plate.
Where very large surfaces or narrow channels are to be etched out, this method
of etching is subjected to a modification to wit:
For the purpose of preventing the printing ink from forcing its way in between
adjacent raised portions of the original plate, which would cause an indistinct
print, I deepen these parts of the plate still more, but as a further action of the
acid of this strength (of 15°) would result in an inevitable destruction of the finer
lines of the drawing I proceed in the following manner:
e.) I carry a printing roller moistened with a solution of dextrine over the well
cleaned and dryed surface of the plate repeatedly to and fro and thus moisten the
raised portions of the same and their edges with the solution of dextrine.
Then I sprinkle the plate with a fine powder of plaster or preferably of sulphate
of baryta (both of which are insoluble by nitric acid) and thus protect the covered
parts against the action of the acid.
When the dextrine has dried I eject the plaster or sulphate of baryta from the
cavities by means of bellows.
f.) Having thus secured the edges of the raised portions against the action of the
acid I bring the zinc plate back into the vat but now employ a more diluted
solution of the acid (only 8-10%) and let it act until the plate is perfect.
If very deep cavities are to be produced the process mentioned sub e has to be
repeated after a careful cleaning of the plate, as the protecting covering mollifies or
softens under the action of the corroding liquid.
Where no large surfaces to be etched are adjacent to fine lines the operations
enumerated sub e. and ƒ may be replaced by a finishing operation with the graver.
Where no fine lines are required the operations described sub e and ƒ may be
dispensed with as then the operations enumerated sub a, b, c and d may safely be
used for etching to any desirable depth.
When the etching has attained the requisite depth the plate is cleaned and then
the etching ground is removed by careful heating.
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
I claim is:
The new
or improved process of etching for the production of an original
matrice-die from a zinc plate (principally intended to be used for the production of
imitations of wood but which plate may also be etched to be used for other
purposes) substantially in the manner and for the purposes herein described and
set forth.
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