Improvements in the Manufacture of Artificial Stone.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Artificial Stone.
I, GUSTAV ADOLF KIEFER, Architect, of Pappenheim, Bavaria, do hereby declare
the nature of this invention to be as follows:-..
The object of my improvements is to manufacture an artificial stone capable of
indefinitely resisting exterior influences. This stone is obtained by mixing, in a
determined order: plaster specially manufactured for this purpose and prepared
with a solution of borax,-hydraulic lime treated with sulphuric acid, and an
inert material which may be sawdust, the debris of peat, dust, ashes, sand etc.
It has already been tried, but in vain, to transform a mixture of ordinary
plaster and of lime (quicklime) by means of sulphuric or sulphurous acid into a
solid crystallized mass. Practice has shown that this process did not produce the
results expected because:
1st. When sulphuric acid is employed the transformation of the caustic lime
into sulphate of lime is instantaneous, so that an intimate combination is not
obtained between the plaster and the lime: 2nd. When sulphurous acid is
employed, the crystallization of the ordinary plaster, which without this takes
places very slowly, is so much reduced that a sufficient consistency of the mass
cannot be obtained to make use of it as stone.
The process forming the object of my application avoids these disadvantages.
To obtain this result the following operation is employed: Pulverized hydraulic
lime is mixed with a certain quantity of water, then partially transformed, by the
addition of sulphuric acid at 66° Baumé, into sulphate of lime, so as to obtain
later on a more intimate and more rapid combination with the plaster; afterwards
the inert material, which according to requirements may consist of saw-dust,
the debris of peat, dust, ashes, sand etc., is added, and intimately mixed with
the sulphated lime. Finally, the plaster carefully calcined for this purpose, and
which if it is necessary has been prepared with a solution of borax is added; it
immediately and very intimately combines with the mass; all that remains is
to run the latter into moulds, where it rapidly sets assuming the consistency of
stone.
It should be remarked that the employment of ordinary commercial plaster
must be absolutely avoided in this method of manufacture of stones, for such
plaster will not enter into combination at all with the mass above indicated and
hardens much less.
The following are examples of the proportions in which the materials may be
employed.
50 litres of water,-7'5 kilogrammes of pulverized hydraulic lime, litre of
sulphuric acid at 66° about 8 kilogrammes of sawdust, 35 kilogrammes of plaster
finely crusted and well calcined.
1
Or again: 45 litres of water,-75 kilogrammes of pulverized hydraulic lime,
litre of sulphuric acid at 660,-185 kilogrammes of slag.
I am not unaware that the manufacture of stones by means of a mixture of

page_text: cement, plaster and sand, stirred together with sulphuric acid so as to obtain
a paste, has been already known for a long time, but this mixture could not be
solidified into blocks except by the aid of great pressure; my process is dis-
tinguished essentially from the latter by the fact that, owing to the mixture of
the substances being effected in an invariable well determined order and to the
employment of well calcined plaster, it enables the object to be effected without
pressure; in fact if the mixture as prepare it is run into moulds in the state of
a stiff paste, without pressure, it sets by itself in a short time and forms, when
it has been dried by the air, a hard and sound block.
Dated this 22nd day of October 1898.
ALLISON BROS.,
Agents for the Applicant.
I, GUSTAV ADOLF KIEFER, Architect, of Pappenheim, Bavaria, 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 application for patent relates to the manufacture of artificial stone capable
of indefinitely resisting exterior influences. This stone is obtained by mixing, in
a determined order: plaster specially manufactured for this purpose and prepared
with a solution of borax,-hydraulic lime treated with sulphuric acid, and an
inert material, which may be sawdust, the debris of peat dust, ashes, sand, etc.
It has already been tried, but in vain, to transform a mixture of ordinary
plaster and of lime (quick lime) by means of sulphuric or sulphurous acid into a
solid crystallized mass. Practice has shown that this process did not produce the
results expected because:
1st. When sulphuric acid is employed the transformation of the caustic lime
into sulphate of lime is instantaneous, so that an intimate combination is not
obtained between the plaster and the lime: 2nd. When sulphurous acid is
employed, the crystallization of the ordinary plaster, which without this takes
places very slowly, is so much reduced that a sufficient consistency of the mass
cannot be obtained to make use of it as stone.
The process forming the object of my application avoids these disadvantages.
To obtain this result the following operation is employed: Pulverized hydraulic
lime is mixed with a certain quantity of water, then partially transformed, by the
addition of sulphuric acid at 66° Beaumé, into sulphate of lime, so as to obtain
later on a more intimate and more rapid combination with the plaster; afterwards
the inert material, which according to requirements may consist of saw-dust,
the debris of peat, dust, ashes, sand etc., is added, and intimately mixed with
the sulphated lime. Finally, the plaster carefully calcined for the purpose, and
which if it is necessary has been prepared with a solution of borax is added; it
immediately and very intimately combines with the mass; all that remains is
to run the latter into moulds, where it rapidly sets assuming the consistency of
stone.
It should be remarked that the employment of ordinary commercial plaster
must be absolutely avoided in this method of manufacture of stones, for such
plaster will not enter into combination at all with the mass above indicated and
hardens much less.
The plaster employed is obtained in the ordinary manner, that is to say by the
calcination of gypsum. But this calcination is effected with greater care than

page_text: usual, that is to say that it is carried on until the gypsum has lost the whole
of its water, whereas commercial plaster still retains more or less water.
The plaster thus obtained is pulverised, and the powder resulting may be
employed in two different manners:
. It may be added just as it is to the sulphate of lime artificially obtained
and mixed with inert material.
b. It may be mixed with a solution of borax, and the mixture obtained may
be added to the sulphate of lime mixed with inert material.
The following are examples of the proportions in which the materials may be
employed.
50 litres of water,-75 kilogrammes of pulverized hydraulic lime, litre of
sulphuric acid at 66°-about 8 kilogrammes of sawdust,—35 kilogrammes of plaster
finely crusted and well calcined.
Or again 45 litres of water,-7'5 kilogrammes of pulverized hydraulic lime,—
litre of sulphuric acid at 66°,-18'5 kilogrammes of slag.
The slag employed is the ordinary slag from blast furnaces which has been
pulverized.
I am not unaware that the manufacture of stone by means of a mixture of
cement, plaster and sand, stirred together with sulphuric acid so as to obtain
a paste, has been already known for a long time, but this mixture could not be
solidified into blocks except by the aid of great pressure; my process is dis-
tinguished essentially from the latter by the fact that, owing to the mixture of
the substances being effected in an invariable well determined order and to the
employment of well calcined plaster, it enables the object to be effected without
pressure, in fact if the mixture as I prepare it is run into moulds in the state of
a stiff paste, without pressure, it sets by itself in a short time and forms, when
it has been dried by the air, a hard and sound block.
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. A process of manufacture of an artificial stone which consists in stirring
pulverized hydraulic lime into a certain quantity of water, then partially trans-
forming it into sulphated lime by the addition of sulphuric acid, afterwards
adding inert material which may be saw-dust, debris of peat, dust, ashes, sand,
etc., and mixing it intimately with the sulphated lime, then adding plaster-
carefully prepared by further calcination—which at once combines intimately with
the mass, and running the latter into moulds where it sets in a short time and
is transformed into a hard and sound block.
2. In carrying out the process of manufacture set forth in the preceding claim
the employment of plaster specially calcined for the purpose and prepared with a
solution of borax as above indicated with the object of obtaining an intimate
combination with the entire mass and the setting into a sound mass.
Dated this 15th day of August. 1899
ALLISON BROS.,
Agents for the Applicant.