Artificial Lithographic Stones, and other similar Bodies.
Year: 1884

page_text: Artificial Lithographic Stones, and other similar Bodies.
I FRANK WIRTH, of the firm of Wirth and Company, Patent Solicitors at
Frankfort-on-the-Main, in the Empire of Germany do hereby declare the nature
of the said invention for "IMPROVEMENTS IN THE MANUFACTURE OF ARTIFICIAL
STONES, ESPECIALLY ARTIFICIAL LITHOGRAPHIC STONES AND OTHER SIMILAR
BODIES" to be as follows :-
Hitherto the use of cement for the preparation of plaster, artificial stone etc
bas labored under the disadvantage that the material cracks after hardening in
consequence of shrinkage, this being more or less due to change in the temperature
and weather. Trials bave been made to overcome this difficulty by mixing the
cement with sand, but the resulting product was only applicable to common purposes,
such as plastering walls, or casting stone blocks and not to finer objects such as an
imitation marble or polished surfaces. The reason of this is that owing to the.
varying hardness of the silica a smooth polish is not obtainable.
This invention overcomes the difficulties mentioned above and enables a homo-
genous cement mass to be produced which after hardening never shrinks, even
under the influence of changes of temperature or weather, moreover it possesses a
perfectly even surface which admits of being polished.
This Invention offers therefore the possibility of making artificial lithographic
stones equal in every respect to the natural ones and in some respects superior as
they can be made to any required form especially in the form of rollers.
The principle of the invention consists in the preparation of blocks or rollers
without cracks or holes and in making them of the same density by impregnation
as the natural lithographic stones.
The first part is carried out as follows: The cement while still in a soft state
(unset) is mixed with an equal quantity, or rather more, of cement that has already
become hardened, in order to prevent shrinkage. Finely ground carbonate of lime
can be used in the place of already hardened cement, in which case the objects
appear of a whiter color. A scientific explanation of above described property of
old hardened cement or of carbonate of lime cannot be given, just as little as the
changes which cement undergoes on hardening is scientifically unexplained,

page_text: The Inventor considers as a better and more likely explanation that in mixing
the new with the old, already hardened cement, a compound is formed which
possesses less shrinking qualities than the cement by itself."
The process is as follows: Generally speaking one half of the cement to be
worked or rather more is made into a paste with water and formed into thin plates
and allowed to harden as quickly as possible if necessary by the aid of heat.
Before becoming too hard the plates are moistened with water and again heated
until owing to these sudden changes of temperature to which the plates are
subjected, they appear full of cracks.
The plates are then ground to a fine powder and mixed with the remaining
portion of the cement in a soft state. This mixture of the fresh cement and the
already hardened cement or carbonate of lime is transferred into a form of cast
iron, of cylindrical shape or made of plates, divided into two compartments by a
perforated plate lying in a horizontal direction and covered with linen cloth.
On this plate the material is allowed to dry and then exposed to a pressure of
over 20 atmospheres. Afterwards a sufficient amount of water is poured over the
pressed mass. as is necessary for the hardening of the whole and this water is
sucked through the mass by means of an air pump, or other convenient apparatus,
placed underneath the perforated bottom. By this means all the air is removed
and the displaced bubbles filled up with the turbid fluid.
After this operation the mass freed from air bubbles receives a second pressing
(by means of a press) of over 20 atmospheres, whereby the excess of water is
got rid of and the molecules of the mass approach each other nearer.
The subsequent condensing of the plates or rollers prepared in the manner
described above takes place with the aid of water which has been drawn off from
its admixture with cement and holding the alkaline soluble portion of the cement
in solution. This liquid is prepared as follows. Cement is made up with 100% of
water and by constant agitation its hardening is prevented until a fine sludge is
formed which has the appearance of finely slaked lime and the water in which the
soluble portions of the cement are contained, poured off. The same is forced
through the solidified and hardened stone and thereby the most microscopic bubbles
are filled out by the soluble constituents contained in the water.
This manipulation may be repeated as often as necessary after the stone or roller
has become dry.
Stones prepared by this process are in no wise inferior to the natural lithographic
stone, repeated experiments proving that impressions taken from the artificial
stone are sharper than such taken from the natural Solenhofer stone.
As an indication that the impregnation of the stone has been carried out to the
necessary degree the following may be mentioned. a. That it does not absorb
water b. That on grinding it with fine stones without the aid of any polishing
medium, a certain degree of polish is observable on it.
The lithographic stones or rollers thus prepared require as such no special
treatment with regard to applying colors, or causticising etc. which is not the case
with the natural stone.

page_text: I FRANK WIRTH of the firm of Wirth and Company, Patent Solicitors at
Frankfort-on-the-Main, in the Empire of Germany, do hereby declare the nature
of the said Invention for "IMPROVEMENTS IN THE MANUFACTURE OF ARTIFICIAL
STONES, ESPECIALLY ARTIFICIAL LITHOGRAPHIC STONES AND OTHER SIMILAR BODIES
"
a communication to me by Louis Rosenthal, a person resident at Frankfort-on-
the-Main, in the Empire of Germany, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:-
Hitherto the use of cement for the preparation of plaster, artificial stone, etc,
has labored under the disadvantage that the material cracks after hardening in
consequence of shrinkage, this being more or less due to change in the temperature
and weather. Trials have been made to overcome this difficulty by mixing the
cement with sand, but the resulting product was only applicable to common
purposes such as plastering walls or casting stone blocks and not to finer objects,
such as imitation marble or polished surfaces. The reason of this is that owing to
the different hardness of the silica and cement a smooth polish is not obtainable.
This Invention overcomes the difficulties mentioned above and enables a
homogenous cement mass to be produced which after hardening never cracks,
even under the influence of changes of temperature or weather; moreover it
possesses a perfectly even surface which admits of being polished.
This invention offers therefore the possibility of making artificial lithographic
stones equal in every respect to the natural ones, and in some respects superior,
as they can be made to any required form especially in the form of rollers.
The principle of the invention consists in the preparation of blocks or rollers
without cracks or holes and in making them by impregnation of the same density
as natural lithographic stones.
The first part is carried out as follows:-
The fresh unset cement is mixed with an equal quantity or rather more, of
cement that has already become hardened, in order to prevent shrinkage. Finely
ground carbonate of lime can be used in the place of already hardened cement, in
which case the objects appear of a whiter color. A scientific explanation of the
property possessed by old hardened cement and by carbonate of lime of depriving
fresh unset cement of its capacity to shrink cannot be given just as the changes
which cement undergoes on hardening are scientifically unexplained.
It would seem that by the addition to fresh cement of the old already hardened
cement or of carbonate of lime a compound is formed which possesses less shrinking
qualities than the cement by itself.
The process is as follows:-Generally speaking one half of the cement to be
worked or rather more is made into a paste with water and formed into thin plates
and allowed to harden as quickly as possible, if necessary by the aid of heat. To
increase the hardness to the utmost extent the plates are repeatedly moistened
with water and heated until, owing to these sudden changes of temperature to
which the plates are subjected, they appear full of cracks.
The plates are then ground to a fine powder and thoroughly mixed with the
remaining portion of fresh cement. This mixture of the fresh cement and the
already hardened cement or carbonate of lime is transferred into a cast iron
mould of a shape to form cylinders or slabs as desired which is divided into two
compartments by a horizontal perforated plate covered with linen cloth.
On this plate the dry material is exposed to a pressure of over 20 atmospheres.
The quantity of water necessary for the setting of the whole is then poured over
the pressed mass and this water is sucked through the mass by exhausting by means
of an air pump or other convenient apparatus, the air from the perforated bottom.

page_text: By this means all the air is removed and the displaced bubble holes filled up with
the turbid fluid.
After this operation the mass freed from air bubbles receives a second pressing
(by means of a press) of over 20 atmospheres; whereby the excess of water is got
rid of and the molecules of the mass approach each other nearer.
The subsequent condensing of the plates or rollers prepared in the manner
described above is effected with the aid of water which has been drawn off from
its admixture with cement and holding the alkaline soluble portion of the cement
in solution. This liquid is prepared as follows: Cement is made up with 100% of
water and by constant agitation its hardening is prevented until a fine sludge is
formed which has the appearance of finely slaked lime and the water in which the
soluble portions of the cement are contained, poured off. The same is forced
through the solidified and hardened stone and thereby the most microscopic bubble
holes are filled out by the soluble constituents contained in the water.
This manipulation may be repeated as often as necessary after the stone or roller
has become dry.
.
Stones prepared by this process are in no wise inferior to the natural litho-
graphic stones, repeated experiments even proving that impressions taken from
the artificial stone are sharper than such taken from the natural Solenhofer stone.
As an indication that the impregnation of the stone has been carried out to the
necessary degree, the following may be mentioned: (a) That it does not absorb
water (b) That on grinding it with fine stones without the aid of any polishing
medium, a certain degree of polish is observable on it.
The lithographic stones or rollers thus prepared require as such no special
treatment with regard to applying, colors or causticising etc, which is not the
case with the natural stone.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim is
1st The preparation as herein described of a cast mass of cement free from faults
and cracks made by mixing fresh unset cement with an equal quantity or rather
more of cement which has already become hardened (set) or finely ground carbonate
of lime.
2nd The preparation of artificial lithographic stones or rollers from cement by
mixing unset coment with about an equal quantity of already set cement, finely
powdered or in lieu thereof with finely powdered carbonate of lime, then subjecting
this mixture to a high pressure forcing a quantity of water necessary for its
hardening or setting through it by exhaustion, and finally again subjecting the
moist mass to a high pressure, substantially as herein specified.
3rd The impregnation of lithographic stone rollers or other objects made of 4
cement with a liquid saturated with the alkaline and soluble constituents of cement
(prepared by stirring cement up with water and pouring off the liquid) until the
object under preparation by merely grinding (without the aid of polishing mediums)
show a polish as herein specified.
4th The preparation of artificial stones from an hydraulic mass, by pressing the 4
mass before it has perfectly set and at the same time exhausting the air out of
the said mass substantially in the manner and for the purpose as described.
Dated this 24th day of November 1884.