Processes for the Manufacture of Artificial Stone.
Year: 1899

page_text: Date of Application, 9th May, 1899-Accepted, 2nd Sept., 1898
COMPLETE SPECIFICATION.
Processes for the Manufacture of Artificial Stone.
I, CHARLES WOODBURY STEVENS, of Monadnoch Building, Chicago, Illinois, in
the United States of America, 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;―
This invention relates to improvements in processes for the manufacture of
artificial stone and has for its primary object a process whereby either solid or
hollow, plain or ornamented artificial stone may be produced adaptable for any
building purposes, such as cornices, courses, fronts or any other purpose to
which natural stone is generally applied in building, and at the minimum cost
both of material and workmanship and of such simplicity as to avoid the neces-
sity for the employment of skilled labour.
In carrying out my process any suitable form of apparatus may be employed,
but I have found by practise that the apparatus illustrated in the accompanying
drawings possesses many advantages over any other apparatus known to me. In
the practise of my invention, besides the apparatus for determining the shape of
the moulded artificial stone, there must be employed some suitable kind of
stone producing compound and some form of moulding material. To produce
the best results the stone-compound should have as a body ground natural stone
of the colour and character desired to be imitated, mixed with some suitable and
proper cement in a dry powdered form so that when the compound is wet a
chemical action takes place that results in hardening the compound to a stone,
when the mass is dry. The moulding material may be ordinary moulding sand,
but I have found in the practise of my invention that such material necessarily con-
tains loam and other foreign substances, which, when wet, discolour the stone-
compound and do not easily retain their moulded shape. For this reason I find
the best moulding material to consists of ground-stone or glass sand, which are
always clean and which will retain their moulded shape while thoroughly satu-
rated with water.
In the practise of my method the materials may be manipulated in two ways.
One way I designate as the "wet process" in which the stone producing compound
is moulded and manipulated in a wet or plastic state while the moulding material
is in a comparatively dry state and relied upon to extract or absorb the moisture
from the stone-compound. The other way I designate the "dry process' " in
which the stone producing compound is moulded and manipulated in a dry
powdered form while the moulding material is in a wet or substantially saturated
condition, the dry stone-compound in this instance absorbing the moisture, neces-
sary to produce the chemical action, from the wet moulding material.
In carrying out my processes, either wet or dry, the same apparatus can be used
and practically the same steps followed and it will therefore be sufficient to
describe but one practise of the process, to wit, the wet process in connection
with the illustration of the preferred form of apparatus for carrying out the
same, which apparatus is illustrated in the drawings, in which:-

page_text: Figure 1 represents a perspective view of a typical completed hollow stone
as produced by my process.
Figures 2 to 7, inclusive, illustrate one way of using my preferred form of
apparatus in carrying out my process, as will be described in detail further on.
Figures 8 to 11, inclusive, represent detail views illustrating a further use
of my invention for producing a superior article of manufacture by my process
as will be described in detail further on.
While my process is adaptable to the manufacture of any kind, form or con-
figuration of stone, it is particularly applicable to what is called hollow stone,
resembling in shape the ordinary terra-cotta hollow building tiles with strengthen-
ing cross webs for cornice work, ornamental course work, entire fronts and the
like and I will therefore describe my process in detail as employed in the manu-
facture of such hollow stone, it being understood, of course, that the apparatus,
even of my preferred form, must be varied as to dimensions, configuration and
use according to the article which it is desired to produce.
Referring now to the drawings, I will first say that we will assume the form
of hollow stone illustrated in Figure 1 is sought to be produced by the apparatus
in the manner illustrated in Figures 2 and 7.
I first take a box a of suitable dimensions, corresponding to a moulder's flask,
the inner walls of which I prefer should serve as the faces against which all of
the outer plane faces of the stone article shall be moulded, except the ornamented
and opposite faces thereof. In the bottom of this box I place a suitable layer b
of moulding material, such as fine moulder's sand, ground-stone or glass-sand
of any suitable thickness and in a just sufficiently moistened condition to hold
its form when pressed to any desired shape. In other words, I propose to have
this moulding material as dry as possible for the intended purpose. Into this
moulding material, with a suitable pattern, I impress the shape of the ornamented
face desired, such for instance the face c of the stone illustrated in Figure 1,
which pattern should, preferably, extend over the entire area of the interior of
the box.
I next pour into the impression thus made the stone-compound in a plastic
or semi-liquid state, sufficiently wet to flow easily, and to a depth corresponding
with the desired thickness of the hollow stone. This compound may consist of
any stone producing mixture of materials and may be either coloured through-
out, or mixed to produced a mottled effect or to produce contrasting colours on
the face of the ornamental stone and in fact different colours of the compound
may be poured to form different parts of the ornamented face. This first manipu-
lation, as far as described, is illustrated in Figure 2. I next insert the parting
boards at the vertical sides of the box, which are faced with metallic facing
plates e of a suitable form upon the interior of the box. Both the parting boards
and facing plates rest upon the back or top of the ornamented stone facing and
preferably extend a little beyond the upper edges of the box. I then fill in the
box, say to about one half its depth (or to any other point according to the
number of strengthening webs desired), with the moulding material, as at g, in
as nearly dry a state as is practicable and upon this moulding material filling,
pour a suitable layer of the stone-compound in a plastic or semi-liquid state.
Figures 3 and 4 serve to illustrate the use of the apparatus as thus far described.
I next fill in with more moulding material, practically dry, nearly to the top
of the box, as illustrated at h in Figure 5. Having now formed in the moulding
material, the ornamented front wall f and the strengthening web at the centre of
the hollow stone, I next successively draw out the parting boards d and pour into
the spaces formed by them the stone-compound which flows down to and unites
with the front f, thereby forming the sides j of the hollow stone, as illustrated
in Figure 6.
I next withdraw the facing plates e as illustrated in Figure 7, and fill in to
the top of the box with the stone compound, which unites with the sides j, and
the strengthening web or partition and forms the back wall of the hollow

page_text: stone. The hollow stone is now completely moulded and may now be laid aside
for setting or curing in any well known or desired manner, according to the
compound used.
The use of the parting boards is desirable as will be readily seen in order to
have a wall to build against and at the same time which may be withdrawn to
allow the stone compound to flow in and take its place. The use of the metallic
face plates, in connection with the parting boards, is also very desirable, because
neither the moulding material nor the stone-compound will adhere thereto as they
would to the parting boards, and hence when withdrawn they leave comparatively
sharp and square edges as between the stone material and the moulding material,
thus producing an article of superior finish. I may also say that if found
desirable the top layer of stone-compound, forming the back k of the hollow
stone, may be covered with a sufficient layer of moulding material to properly
aid in the absorption of the moisture from this part of the compound and at
the same time protect the same against the direct action of the atmosphere
thereon, which might in some cases produce weather checking.
It. will, of course, be understood that I have herein illustrated and described
the simplest form of apparatus and a type of the simplest form of hollow stone
which can be produced by my process, and it will, of course, be understood in
the making of artificial stone of different shapes, contours and dimensions, the
box, the parting boards and the facing plates must be modified accordingly, for
obviously hollow stone, with both ornamented sides and ends or with obliquely
or otherwise disposed ornamentation and contour, extending in various direc-
tions, may be produced by my process without any variation whatever in the
process and practically no variation in the apparatus, excepting that the use of
the parting boards and facing plates would probably in all cases be limited to
the plane surfaces, although that is not absolutely essential because the blocks
may be moulded, with either top, bottom, sides or ends uppermost or in an
oblique position according to the particular article being made.
I have also found by practical experience that in the moulding of either delicate
or intricate ornamental designs, the best results can be obtained by first filling
in the impression of the pattern made in the moulding material, to the depth
of about an eighth of an inch with dry stone-compound and backing it up with the
liquid compound because the fine lines and sharp edges will be better brought
out, the dry powdered stone-compound entering the depression formed by the
pattern more perfectly than the plastic or semi-liquid compound.
I have also found that where it is desirable greater strength may be given the
hollow stone, either laterally or longitudinally, than is afforded by the strengthen-
ing web or partition formed therein in the moulding of the stone, by providing
posts extending between the exterior walls, either front and back or sides, and
also if desired between the partitions and the external walls. These posts are
formed of the stone-compound in the manner about to be described, it being
understood that in both cases the posts are formed before the hollow stone is
allowed to set or is cured; in other words am able to produce by this process
an article superior in strength to that produced by any other process and by the
use of the same apparatus employed in carrying out the process.
In producing a hollow stone thus strengthened, of the form illustrated in
Figures 1 to 8 of the drawings, I would take a tube /, preferably metallic, and
after the stone is completed, as illustrated in Figure 7, I would force the tube
through both the back wall and partition i, partly through the front f, and
of course through the moulding material fillings or layers g and h and then
withdraw the tube, carrying with it the moulding material and stone compound
by which it will be filled. As many of these holes as desirable may be formed
along the length of the stone and then filled with the plastic or semi-liquid
compound up to a level with the surface of the back wall k. Each post will form
a homogeneous union with the back and front walls and the partition, besides
extending there between, so that when the filling of moulding material is removed

page_text: from the stone, these posts will serve as braces between the front and rear wall
and the partition or strengthening web. In Figure 8 I have illustrated a vertical
section of the moulding box with the stone complete, showing the manner of
using the tube / to form the posts. In Figure 9 I have illustrated a horizontal
section of the same but showing some posts completed and others with the tubes
in place preparatory to making the holes for the posts.
In Figures 10 and 11 I have shown how a hollow stone, formed with its
ornamented face down and having a strengthening web at right angles to the back
wall thereof, may be provided with posts extending through such partition or
web and between the upper and lower walls or sides of the block parallel with
the back wall. In such case I prefer to employ a hinged top m and a hinged
side n for the mould box, in order that the posts may be formed through the
sides of the hollow stone after the same has been formed face downward or in
a position at right angles to that in which the posts are formed.
In this apparatus it will be noticed that the parting board d has a facing
plate e on each side thereof to form the strengthening web and it will, of course,
be understood that the same means can be adopted for forming the side walls j,
in which case, of course, the side parting boards & would be set a suitable distance
away from the sides of the box or flask and a layer of moulding material would
intervene between said boards with their double facings and the sides of the box.
The stone will thus be formed by molding the stone-compound wholly in
moulding material, that is, with moulding material on all sides or upon each
side of each layer of the compound.
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―
1.) The process of forming artificial stone consisting in moulding the stone-
compound in or on the mould formed of moulding material, one of which shall
be in a wet or plastic state, and the other in a relatively dry state, and then
allowing the mass to set until the dry element absorbs the surplus moisture
from the wet element, thereby converting the stone compound to a solid or non-
liquid form, substantially as and for the purpose set forth.
2.) The process of forming artificial stone consisting in moulding the stone
compound while in a plastic or semi-liquid state, in or on a mould formed of
relatively dry moulding material and then allowing the mass to set until the
moulding material absorbs the surplus moisture from the compound, thereby
converting the latter to a solid or non-liquid form, substantially as and for the
purpose set forth.
3.) The process of forming artificial stone consisting in moulding stone com-
pound while in a plastic or semi-liquid state, in or on a partial mould formed of
relatively dry moulding material, and then covering the compound with relatively
dry moulding material and finally allowing the mass to set until the moulding
material absorbs the surplus moisture from the compound, thereby converting
the latter to a solid or non-liquid form, substantially as and for the purpose
set forth.
4.) The process of forming artificial stone consisting in moulding layers of
stone-compound while in a plastic or semi-liquid state between or on layers of
relatively dry moulding material, and then allowing the mass to set until the
moulding material absorbs the surplus moisture from the compound, thereby
converting the latter to a solid or non-liquid form, substantially as and for the
purpose set forth.
5.) The process of forming artificial stone consisting in first moulding layers
of stone compound while in a plastic or semi-liquid state between or on layers of
relatively dry moulding material, then removing a portion of such layers of com-
pound and moulding material and replacing such removed portions with stone
compound in a plastic or semi-liquid state and finally allowing the mass to set until

page_text: the moulding material absorbs the surplus moisture from the compound thereby
converting the latter to a solid or non-liquid form, substantially as and for the
purpose set forth.
6.) The process of forming artificial stone consisting in first forming in rela-
tively dry moulding material a partial mould of one or more faces of such stone,
next filling into the partial mould thus formed a lining or layer of stone-com-
pound in a dry powdered state, then moulding thereon a layer of stone-compound
in a plastic or semi-liquid state, next covering the compound with relatively
dry moulding material and finally allowing the mass to set until the moulding
material absorbs the surplus moisture from the compound, thereby converting
the latter to a solid or non-liquid form, substantially as and for the purpose set
forth.
MARKS & CLERK,
18, Southampton Buildings, London, W.C.,
13, Temple Street, Birmingham, and 25, Cross Street, Manchester,
Agents.