Process of Manufacture of Artificial Marble.
Year: 1892

page_text: Date of Application, 26th May, 1892
Complete Specification Left, 27th Feb., 1893-Accepted, 6th May, 1893
PROVISIONAL SPECIFICATION.
A Process of Manufacture of Artificial Marble.
We, HUGO ADALBERT MAJEWSKI, Schoolmaster, of Putbuserstrasse 34 and
WILHELM BEYENBACH, Chemist, of Brunnenstrasse 73, both in Berlin, in the
German Empire, do hereby declare the nature of this invention to be as
follows:-
Gypsum or plaster, freed from moisture and burnt, may, by impregnation in
solutions of quickly crystallizing salts, be hardened and coloured, so that it acquires
a very attractive appearance. This fact, borne out by experiment, has not, however,
been taken advantage of to any considerable extent, in the manufacture of stone
for purposes of statuary, owing to certain difficulties which have hitherto baffled
the attempts made in that direction. The main cause of the failures experienced
resides in the fact that the salt solutions required for saturating gypsum, fail to
penetrate the stone to a sufficient depth, as they become crystallized almost at the
surface of the block and thereby themselves close up the passages through which
they might otherwise reach the interior.
It has been for some time the applicants' endeavour to remedy this drawback,
and this led them to the discovery of a liquid, which while facilitating the admission
of the readily crystallizing salts to the very core of the stone, does not itself
produce any effect on the latter, though it is capable of combining with the salts
subsequently used for saturation in such a manner as to render the stone proof
against atmospheric influences and dampness.
Thus, a concentrated solution of sulphite of potassium in the present process acts
as a vehicle for the solutions of salts subsequently to be conveyed into the body
of the stone; and it in all cases performs its task by enveloping, as it were, the
molecules of the sulphate of lime. Besides, as this solution of sulphite of potassium
is slow in crystallizing, it counteracts the tendency of the solutions of salts,
subsequently employed, to deposit too quickly their crystals in the pores. Thus
the salt solutions will freely penetrate the stone so long as the liquid acting as a
vehicle does not itself combine with the salts and become crystallized. It will be
understood that to attain this object the stone should not be allowed to become
completely saturated with the liquid vehicle, as, if the pores are entirely filled up,
the inward sucking action naturally ceases. It is therefore sufficient for the stone
to draw in just a slight quantity of the said liquid vehicle.
In the case of large sized blocks, however, natural suction will not be found
sufficient to carry the solutions right into the interior of the stone, as owing to the
slow capillary action, crystallization will generally set in too soon to allow of any
deep penetration of the solution. Capillarity ought therefore in this case to be assisted
by suitable suction.
Without the liquid pore-opening medium or vehicle referred to, the salt solutions,
capable of imparting to the stone the properties and colour of marble, can hardly in
any case sufficiently pervade the structure of the stone to accomplish the desired
purpose.
The transformation of gypsum or plaster into marble-like artificial stone is therefore
carried out in practice substantially as follows:
A block of gypsum of comparatively old formation is roughly hewn or cut to the
desired shape, and then from 70 to 80% of the moisture it contains is extracted.
The material thus practically freed from moisture is next placed in a bath consisting
of a concentrated solution of sulphite of potash, a small quantity of which it is

page_text: allowed to draw in, after which it is left to dry at the surface. The stone is now
capable of absorbing hardening and colouring salt solutions, among which sulphates,
chromates and cyanides, are to be preferred.
Articles of but small thickness are simply immersed in the desired solutions.
Within 24 hours the gypsum will be seen to alter its appearance, when it may be
placed in a well ventilated room heated to about 30° C., until the crystallization is
completed.
In the case of articles of considerable thickness, however, the preliminary suction
process above referred to is preferably carried out as follows:-
The stone is to a great extent perforated longitudinally and then placed into the
baths of the liquid vehicle or the crystallizing solutions, as the case may be, in such
a manner, that the liquid only acts upon the outer surface of the stone; its
perforation being turned upwards is tightly closed by a suction device placed upon
it and through the medium of the vacuum and consequent current of air therein
created a sucking action is produced.
After crystallization the product obtained is capable, like natural stone, of being
utilized for artistic work of any description.
This artificial marble will indeed fully answer the purpose of natural marble,
over which it, moreover, has the advantage that while it equals it in durability and
beauty it is less costly and is capable of at all times accommodating the prevailing
taste or fashion of the period.
Dated this 24th day of May 1892.
W. P. THOMPSON & BOULT,
Agents for the Applicants.
COMPLETE SPECIFICATION.
A Process of Manufacture of Artificial Marble.
We, HUGO ADALBERT MAJEWSKI, Schoolmaster, of Putbuserstrasse 34 and
WILHELM BEYENBACH, Chemist, of Brunnenstrasse 73 Berlin, in the German
Empire, 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 :-
Gypsum or plaster, burnt and freed from moisture (dehydrated), may, by
impregnation in solutions of quickly crystallizing salts, be hardened and have a
fine colour imparted to it. This fact borne out by experiment has not however
been taken advantage of to any considerable extent, in the manufacture of artificial
stone owing to certain difficulties which may be mainly ascribed to the fact that
the salt solutions required for saturating gypsum, fail to penetrate the stone to a
sufficient depth, as they become crystallized almost at the surface of the block
and thereby themselves close up the passages through which they might otherwise
reach the interior.
It has been for some time the applicants' endeavour to remedy this drawback,
and to find means for accomplishing a double object viz.
(1) It was desirable that the readily crystallizing or colouring salts may penetrate
to the very core of the stone; and
(2) Special attention was directed by the applicants to the production of those
exceedingly well crystallizing and durable combinations of two salts (sulphate of
calcium and sulphate of potassium) as it has been found that such combinations
or compounds are calculated to impart to the artificial marble obtained by this
process the greatest possible hardness and to render them proof against atmospheric
influences.
This double problem the applicants have solved by saturating the dehydrated
gypsum with a concentrated solution of sulphite of potassium (K₂SO,).

page_text: The following experiments have been made :
(1. Experiment a.) Dehydrated gypsum (in the shape of a slab 3 centimetres
thick) was immersed for 24 hours in a concentrated solution of alum; with the result
that a superficial layer about centimetre thick was alone crystallized while the
central or innermost part of the slab remained free from saturation and in a chalky
condition.
(Experiment b.) Dehydrated gypsum (in the shape of a slab 3½ centimetres
thick) was immersed for a few minutes only in a solution of sulphite of potassium
and after superficial desiccation placed in a solution of alum; 10 hours after the
whole piece was completely crystallized.
Hence it will be seen that K,SO3 performs the part of a leading liquid or
vehicle for the solution of alum.
(2.) As K₂SO, is a changeable salt, which, when it receives one part of O from
the salts introduced after it and comparatively rich in oxygen, becomes K₂SO,, it
follows that either in the subsequent treatment or even after the gypsum has been
saturated, a bisulphate will be obtained by the combination of sulphate of calcium
and sulphate of potassium.
As the sulphite of potassium becomes oxidized at the expense of the other salts
it separates from them (if these salts be metallic salts) the oxides, hydroxides, or
protoxides they contain. It therefore performs an exceedingly important function
in the colouring of the artificial stone and the colour itself depends upon it. Thus
gypsum saturated with sulphite of potassium will be coloured a deep green if
allowed to crystallize in a violet solution of chrome-alum.
For the subsequent saturation of the gypsum, any well crystallizing salts may be
used such as alum, sesquisulphate of iron and protosulphate of iron, sulphate of
zinc, sulphate of manganese and also the respective chromates and other permanent
combinations.
In the case of large sized blocks however natural suction will not be found
sufficient to carry the solutions right into the interior of the stone, as owing to the
slow capillary action crystallization will generally set in too soon to allow of any
deep penetration of the solution. Capillarity ought therefore in this case to be
assisted by suitable suction.
The transformation of gypsum or plaster into marble-like artificial stone is
therefore carried out in practice substantially as follows,-
A block of gypsum of comparatively old formation is roughly hewn or cut to
the desired shape, and then from 70 to 80% of the moisture it contains is
extracted.
For the purpose of ensuring a thorough saturation or colouring a concentrated
solution of sulphate of potassium should be used as stated above in describing the
experiment b and also in the explanation given in the second paragraph.
Articles of but small thickness are simply immersed in the desired solutions.
Within 24 hours the gypsum will be found to be thoroughly saturated with the
solutions when it may be placed in a well ventilated room heated to about 30° C.
until the crystallization is completed.
In the case of articles of considerable thickness, however, the preliminary
suction process above referred to is preferably carried out as follows,-
The stone is to a great extent perforated longitudinally and then placed into the
baths of the liquid vehicle or the crystallizing solutions, as the case may be, in
such a manner, that the liquid only acts upon the outer surface of the stone, its
perforation being turned upwards is tightly closed by a suction device placed upon
it and through the medium of the vacuum and consequent current of air therein
created a sucking action is produced.
After crystallization the product obtained is capable like natural stone of being
utilized for artistic work of any description.
This artificial marble will indeed fully answer the purpose of natural marble over
which it moreover has the advantage that while it equals it in durability and

page_text: beauty it is less costly and is capable of at all times accommodating the prevailing
taste or fashion of the period.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is,
1. A process of manufacture of artificial marble from natural gypsum or plaster-
stone characterized by the introduction into the block to be treated which has
first been freed from moisture and roughly shaped of a concentrated solution of
sulphite of potassium (K,SO,) which is to act as an opening medium or vehicle for
the crystallizing solutions or compounds with which the block is subsequently to
be treated.
2. In the manufacture of artificial marble the treatment of the natural gypsum
or plaster-stone with a solution of sulphite of potassium substantially as and for
the purpose specified.
3. In the manufacture of artificial marble the provision of perforations in the
blocks in combination with suction devices for the purpose of creating a sucking
action to facilitate the absorption of the solution of sulphite of potassium or of the
hardening or colouring solutions of salts.
Dated this 27th day of February 1893.
WM. P. THOMPSON & BOULT,
Agents for the Applicants.