Improvements in and in the Manufacture of Plaster for Building Purposes.
Year: 1892

page_text: COMPLETE SPECIFICATION.
Improvements in and in the Manufacture of Plaster for Building
Purposes.
A communication by LUDWIG OTTO ROESER-MÜLLER and BENNO DEIKE, both
of Munich, in the Empire of Germany, Architect and Chemist respectively.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of the Agency for
Foreign Patent Solicitors, 6, Lord Street, Liverpool and 6 Bank Street.
Manchester both in the County of Lancaster and 323 High Holborn in the
County of Middlesex, Civil Engineer, 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 has for its object to make the use of plaster, as a building
material (such, for instance, as for forming intermediate floorings, partition walls,
light domes, as filling up material, plaster panels, etcetera) more general and more
valuable by employing such material in a condition or combination in which it has
all the good qualities possessed by plaster as a building material, to a much higher
degree than has hitherto been the case with the previous mode of using it.
The following are the properties which come mainly into consideration:
The lightness and incombustibility of the parts of a building constructed of
plaster, as well as the insulation produced against heat; the suppression of noise,
and the prevention of damp (rot).
-
In order, therefore, as already stated, to increase its proved qualities and
advantages, the plaster is employed in a porous condition and not in the usual
solid condition.
This porosity is produced by chemical means, and in fact by adding to the
gypsum or plaster either bicarbonate of soda, the action of which may be
expedited and increased by the addition of a limited quantity of dilute sulphuric
acid, hydrochloric acid, etcetera, or an acid salt, or bicarbonate of soda and boiling
water.
For 1 cubic centimetre of porous plaster--
500 gr. gypsum
+
700 to 750 gr. water
}
23 gr. bicarb. soda 20 gr. sulphuric acid 5%
.
23 gr. bicarb. soda 15 gr. sulphuric acid 5%.
In place of the acids, equivalent quantities of salts (such as acid tartrates,
acetate of alumina, etcetera) may be employed.
By means of the porosity, a very considerable diminution of weight is obtained
as against solid plaster, and therefore a less weight is suspended on the beams or
other parts of the building to which the layers, fillings, etcetera, of plaster are
applied.
The following is the composition of a filling up material for a cubic metre
of space :-
Sand
Clay
Gravel
-
-
1400 to 1640 kilos. average 1520 kgs.
"
33
2000 kgs.
2000
1500 to 2500
2100

page_text: The porous plaster acts as a bad conductor of heat in consequence of the
insulating layers, as the pores filled with air may be considered to be, whilst noise
is better obstructed than with solid plaster, as less solid bodies are attacked by the
Bound waves.
The formation of house rot or mould is entirely prevented by making the
endangered parts of porous plaster, because, first, it is used in a thoroughly dry
condition, and, secondly, the acids, etcetera, employed in its manufacture, destroy,
at its commercement, the formation of the germs which produce the rot.
The porous plaster, as experiments have shown, may also be exposed to a
temperature (or to direct fire) six times greater than solid plaster before cracking
or tearing takes place.
In order to give the porous plaster a still greater firmness, it is mixed with fir or
pine brushwood, which has been dipped into a suitable agglutinant, and thereby
the plaster mass is given an extreme tenacity combined with the capability of being
easily worked.
In a plaster panel filled in with this substance, for instance, nails, screws, blocks
and the like may be inserted, and drawn out again, without any peeling off taking
place as usual with ordinary plaster or ceiling compositions.
Where this last named quality is mainly of importance, it is preferable to
provide, not the porous but the solid plaster, with an admixture of fir or pine
brush wood, so that the parts constructed of such substance, such, for instance, as
panels, may have a very great firmness and toughness, and, in combination with a
foundation of wood laths, or osiers, or rushes, is especially suitable for making
intermediate floorings, and forming ceiling plaster, because any falling down of the
plaster or bulging or deformation of the ceiling, such as frequently takes place, is
impossible.
This material is also safe from fire to a great extent, as only the particles of
brushwood contained on the outside smoulder, whilst no bursting need be feared,
as is the case with ordinary plaster panels, etcetera, so that the assertion may be
made that, by the use of this porous plaster or of plaster provided with such an
admixture, the fire remains localised.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me by
my foreign correspondents, I declare that what I claim is :-
1. The improvements in the manufacture of plaster which consist in adding, to
the gypsum or ordinary plaster, bicarbonate of soda, together with diluted sul-
phuric, or hydrochloric, acid, acid salts, or the like, or in adding bicarbonate of
soda with boiling water.
2. The improved porous plaster made substantially as hereinbefore described,
for use in building purposes with the object of giving the parts constructed
of such plaster a greater degree of lightness and incombustibility, and of
increasing the properties of obstructing noise, insulation against heat, and pre-
vention of dry rot.
3. The admixture of fir or pine twigs with the porous or with solid plaster,
employed as building material, for the purpose of giving the parts constructed
therefrom an increased solidity and tenacity.
•
Dated this 19th day of April 1892.
WM. P. THOMPSON & CO.,
Agents for the Applicant.