Preparing Designs on Lithographic Stones and Zincographic Plates by Aid of Sand Blast.
Year: 1889

page_text: COMPLETE SPECIFICATION.
Preparing Designs on Lithographic Stones and Zincographic Plates
by Aid of Sand Blast.
I, JOSEPH LEWIS MILLS of Baldwin's Gardens Gray's Inn Road in the County of
Middlesex Art-colour-printer 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 :-
My invention comprises the several processes which are carried into practice in
the modes and by the means hereinafter described. One of these processes is as
follows.
1. I provide a lithographic stone which has been polished with water of air stone,
and I grind the surface of such lithographic stone by rubbing it with sand interposed
between it and another flat stone, or by subjecting it to the sand-blast next I
paint or roll in with a roller the entire grained surface with lithographic, or greasy
ink, soap, or any other suitable greasy lithographic substance, and when the grease
has been perfectly absorbed by the stone, and the superfluous grease has been removed
with turpentine the lithographic surface is then rolled in with Brunswick Black, or
some other suitable preparation until it presents an even and equal appearance. The
condition of the lithographic surface after being thus treated is that of a solid slab
of lithographic grease which is coated or covered over with a thin coating of
Brunswick Black the purpose of which coating is to protect said greasy surface
which lies, immediately under it upon the lithographic stone from the action of the
acid which it is necessary to employ for the etching of the work after the sand-blast
When this
has been applied, and before the work can be efficiently rolled up.
prepared lithographic surface is perfectly dry a tracing of the picture or design,
intended to be engraved is placed thereon, and the artist uses preferably the instrument
or apparatus which I call an air or steam-pencil-for which invention Letters Patent
dated 16th July 1888 No. 10,295-were granted to me-as a free hand tool for
removing with the sand-blast all the parts of the picture, or design which are not
required, and partially removing the parts where more or less strong tints are required,
and leaves untouched the parts which are required to be black. The engraving
part of the process having been finished the work is etched, with acid and water

page_text: and gum, and can then be rolled up with a lithographic roller, and impressions can
be pulled.
2. Another process which is better adapted for more artistic work showing
character and touch of the artist is as follows. A careful tracing having been taken
of the picture to be engraved is placed on the solid greasy slab hereinbefore termed
the lithographic surface, which covers the surface of the lithographic stone, and then
all the darkest parts, lines, and drawings in the picture, are stopped out with a
mixture of gum and glycerine or some suitable resisting varnish and when this
stopping out complete the whole lithographic surface is subjected to a blast of
sand, or fine emery which partially removes the portions of such surface which
are not protected by the gum and glycerine or other suitable resisting varnish, but
does not affect the parts which are covered by such varnish, thus the drawing in
black is preserved in solid form whereas all the other portions of the surface
are punctured by the action of the sand. The next tint to the black, namely
a part of the punctured lithographic surface, is then stopped out still following
the tracing, and the whole lithographic surface is again subjected to the blast which
alternates still more the unprotected parts of such surface, and consequently a third
tint next in value to the second tint and second in value to the solid black which was
punctured first is obtained, and so there have been created the plain black drawing,
the strong gray tone slightly removed from black, and a still lighter tone of gray next
in value to the latter. By repeated stoppings out and applications of the blast other
tones are created until the last suggestion of grain or tint has been attained, and the
bigh lights or white of the picture obtained by wearing away the last portions of the
lightest tint previously created. The work is then etched and rolled up in the usual
manner and an impression is pulled which will have many graduations of tone from
black to white according to the intricacy of the subject.
3-Another of my processes is to cover the surface of a polished lithographic stone
with an equal coating of finely dissolved gum coloured black preferably, and when
this coating is dry to place the offset thereon, and with the sand-blast applied with the
instrument herein before mentioned to make the drawing or design in punctures in the
gum, each grain of sand striking the gunmed surface penetrates it, and thereby
exposes the lithographic stone punctured. When the drawing or design is completed
a lithographic mixture of a suitable greasy nature is poured over the entire surface,
and is removed before it can dissolve the gum thereon. This mixture immediately
penetrates into the lithographic stone through the punctures only, and impregnates
the stone in these parts with grease. The surplus grease then soaked up with a
sponge and the gum is melted away from the surface of the stone leaving only
the lithographic grease or ink which has penetrated through the punctures that
were in the gum. The stone is then etched with acid and gum and water in the usual way
and the work can be inked with the ordinary lithographic roller and impressions
pulled. This is the reverse of the process 1 hereinbefore described in which the printing
is from the surface of the stone which is left intact, after the removal of the part which
is not required, whereas by this process 3 the printing is from the ink which has been
poured into the punctures or the parts which have been chipped out. The work
after being rolled up with ink can be elevated a little by protecting each spot of ink or
puncture filled with the ink with powdered resin and then biting away the stone
with a solution of acid and water. The stopping out process 2 hereinbefore described
is just as applicable to this process 3 as to process 1 first hereinbefore described
when modified as follows. 4. Another process is to coat the lithographic stone with
a smooth coating of gum, and when this coating has dried, to place thereon a
tracing of the picture or drawing required. Upon this dry gumined surface all
the high lights of the picture are stopped out by printing over them in the tracing a
mixture of gum and glycerine which forms a resisting medium to the action of the
sand-blast, and whilst this mixture is still moist the whole surface is subjected to the
action of the sand-blast. The parts stopped out with gum and glycerine protect
the surface of the gummed stone, and thereby create the high lights in the picture,
the remainder of the stone which is covered with the dry gum only is punctured

page_text: by the sand, and thus is created the tint which is next in value to the high lights in
the picture. Next the parts in the last mentioned tint which are required to be
preserved are stopped out with a strong lithographic varnish or paste made of
lithographic ink dissolved in turpentine mixed with a proportion of asphaltum. This
varnish is intended to serve a double purpose, namely as a resist to protect the first
tint created by the action of the sand-blast, and to impregnate the punctures made by
the sand-blast with lithographic grease. After the first tint next to the white has been
stopped out and lithographed simultaneously, the second tint is stopped out with the
lithographic varnish, and the sand-blast is applied to the remainder, and this alternate
treatment of stopping out and applying the blast is continued until the black is
arrived at when the work is completed in the usual way by wiping away the
superfluous lithographic ink, dissolving the gum, and etching the stone with acid.
The work can then be rolled up with the usual lithographic roller, and impressions can
be taken. If it be required the work can be raised by powdering it with resin, and
then biting away the stone with acid.
5. Another process is to engrave on the lithographic stone the subject picture or
design by the means of a blast of sand, emery, or other suitable substance impelled
against the surface to be operated upon, and applied with any suitable instrument or
machine, and afterwards to pass the printing roller charged with the lithographic
ink over the surface of such stone imbuing or impregnating only the parts of such
surface which have not been engraved and leaving the engraved or sunken parts
untouched and so creating any desired printing surface. I either direct the sand-blast
to the plain stone first, and charge the lithographic surface with lithographic ink,
grease, asphalt or other suitable medium afterwards, or I charge the stone with
lithographic ink, grease, asphalt or other suitable medium first and direct the sand-
blast to the lithographic surface afterwards thereby removing the lithographic surface
in places wheresoever it may not be required.
6. Another process is as follows. Having prepared the lithographic surface in the
manner herein before particularly described in process 1, 1 take upon such surface
a photograph of the picture or object intended to be engraved. This photograph
is preferably "Linear," and of any sensitive and more or less dense nature, for example
a bi-chromatized solution of Gelatine, and serves as a resist or stopping out medium
for protecting the parts of the lithographic surface which it covers. I then apply the
sand-blast to the entire surface with any suitable sand-blast apparatus thereby entirely
removing the parts of such surface which are not covered by the photoglyphic or
photographic film, exposing the lithographic stone in these parts and so attaining the
white colour, and thus obtaining a positive lithographic result if the filin is a negative,
and a negative lithographic result if the film is a positive. Wherever the photograph
overlies the lithographic surface the sand does not penetrate the latter, but where the
photograph does not overlie the lithographic surface the sand or such like enters
between the lines, grains, canvas pattern, or stipples and chips away the surface.
Lastly I etch with a suitable etching and roll up in the ordinary way.
For Zincography I prepare the surface of the plate with suitable grease which I
remove in precisely the same manner as is hereinbefore described, then etch with
a suitable etching and roll up in the ordinary manner.
By sand-blast I mean every known form of removing surfaces by the impact of
sand, emery, steel, shot, etc. falling by its own gravitation or impelled against such
surfaces. I do not confine myself to the use of the instrument herein before
mentioned for which I have obtained Letters Patent, as I may employ any suitable
sand-blast apparatus now known for the purpose herein stated. The nearer the
instrument herein before mentioned is held to the lithographic surface the greater is
the cutting force obtained, because the less expansion of the sand occurs, the farther
the less cutting force because of the increased expansion of the sand. If the artist
wants to make fine lines he holds the instrument close to the stone, if he requires
coarser lines he holds the instrument farther off, and if he desires to cover. much
surface with shading he holds the instrument still farther off.

page_text: 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 The preparation of lithographic surfaces in the manner and by the means
hereinbefore described.
2-The removal in an artistic manner of certain portions of such surfaces by sand-
blast as herein before described.
3-The several processes 1 to 6 inclusive hereinbefore described for lithographing
by means of sand-blast.
4-The process for Zincographing as stated in the foregoing Specification.
Dated this 12th day of April 1880
JOSEPH LEWIS MILLS.