Process for use in the Manufacture of Gypsum Objects.
Year: 1891

page_text: Date of Application, 27th July, 1891
Complete Specification Left, 1st Apr., 1892-Accepted. 7th May, 1892
PROVISIONAL SPECIFICATION.
Process for use in the Manufacture of Gypsum Objects.
I, FELIX WACHSMUTH of Querfurt in the German Empire, Banker, do hereby
declare the nature of this invention to be as follows:
The process of this invention is for the purpose of hardening, rendering water
resisting, and colouring objects made from the crude gypsum. The object to be treated
having been made of the desired form the moisture is expelled therefrom by heating
it to from 100° to 150° Celsius. It is then placed in a warm solution of barium
hydrate in which it allowed to remain a longer or a shorter time according to the.
dimensions of the object. In this way the gypsum becomes gradually hardened,
after which it it smoothed and polished, then placed in a 10 per cent., or there-
abouts, watery oxalic acid solution, withdrawn therefrom in a few hours, dried and
polished. It then possesses a hardness surpassing that of marble and is not affected
by water.
The chemical procedure is as follows:
By the impregnation with baryta water the gypsum is in part changed to barium
sulphate and caustic lime. The former is known to be insoluble in water.
By the
subsequent treatment with oxalic acid solution the caustic lime is converted into
oxalate of lime which also is insoluble.
CAPITAINE & VON HERTLING,
89, Chancery Lane, London, W.C., Agents for the Applicant.
COMPLETE SPECIFICATION.
Process for use in the Manufacture of Gypsum Objects.
I, FELIX WACHSMUTH of Querfurt in the German Empire, Banker, 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 :-
The process of this invention relates firstly, to the hardening and rendering
water resisting of objects cut from crude gypsum, and secondly to the colouring of
such objects.
The object to be treated having been made of the desired form, the moisture is
expelled therefrom by heating it at a temperature of from 100° to 150° Celsius.
It is then placed in a warm solution of barium hydrate in which it is allowed to
remain a longer or a shorter time according to the dimensions of the object. In
this way the gypsum becomes gradually hardened, after which it is smoothed and
polished, then placed in a 10 per cent., or thereabouts, watery oxalic acid solution
071

page_text: withdrawn therefrom in a few hours dried and polished. It then possesses a hard-
ness surpassing that of marble and neither the substance or the polish is affected
by moisture.
The chemical procedure is as follows:-By the impregnation with baryta
solution the gypsum is in part changed to barium sulphate and caustic lime. The
former is known to be insoluble in water. By the subsequent treatment with
oxalic acid solution the caustic lime is converted into oxalate of lime which also is
insoluble.
CaSO, Ba (OH),
=========
BaSO + Ca (OH),
Ca (OH), + C,H₂O₁ = CaC₂O, + 2 H₂O.
The objects produced in this way have the colour natural to the gypsum used
and the colouring of the same may be combined with the hardening process by
placing the gypsum after the moisture has been expelled therefrom and previous to
the treatment with baryta solution in a solution of a coloured metal sulphate such as
iron sulphate, copper sulphate, chromium sulphate, etcetera, or in a solution of any
dye or colouring matter. Also the baryta solution or the oxalic acid solution may
have such colouring stuffs added to them as are soluble therein.
Having now particularly described and ascertained the nature of my said inven
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. The process for hardening and rendering water resisting, objects cut from
crude gypsum, consisting in (a) removing the moisture therefrom by the application
of heat and then for the purpose of hardening the same steeping them in a solution
of barium hydrate; (b) treating the objects so hardened with an oxalic acid
solution for the purpose of rendering them water resisting substantially as
described.
2. The colouring of gypsum objects of the kind referred to by impregnating
the gypsum with a colouring solution either previous to the treatment with the
baryta solution or by adding colouring matter to the baryta solution or to the
oxalic acid solution substantially as described.
Dated this 1st day of April 1892.
CAPITAINE & VON HERTLING,
89, Chancery Lane, London, W.C., Agents for the Applicant.