Improvements in the Manufacture of Plaster of Paris and in the Utilisation of Waste or Cheap Materials therefor.
Year: 1889

page_text: Date of Application, 1st Oct., 1889
Complete Specification Left, 1st July, 1890-Accepted, 30th Aug., 1890
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Plaster of Paris and in the
Utilisation of Waste or Cheap Materials therefor.
We, WILLIAM JOHN OSWALD, Cobridge, Stoke-on-Trent, Merchant, JOHN ROGERS
ASHWELL, F.I.C., F.C.S.. 111 Waterloo Crescent, Nottingham, and JOHN ARTHUR
COOKE, 103 Waterloo Crescent, Nottingham, do hereby declare the nature of this
invention to be as follows:-
This invention has for its object the manufacture of plaster from old waste, plaster
moulds or casts.and other like waste or artificially prepared hydrated sulphate of lime.
Enormous quantities of these casts or moulds are at present. thrown away as useless
when done with, or are simply used for whitening floors and the like. Furthermore.
very large quantities of hydrated sulphate of lime being either old plaster of Paris
which has lost its power of hardening, or even precipitates, or waste products of
chemical manufactories can be utilised.
In carrying out our invention the plaster moulds are broken into pieces of convenient
size or even in certain cases ground to powder first, and are then burnt in kilns at a
temperature which is not such as will over burn or dead burn the plaster, for when
this is caused, the plaster on withdrawal from the kiln will not harden in a short time
on mixing with water or the hardening is more or less interfered with.
Whether the material be in the form of powder or lump. special arrangements are.
required so as to thoroughly expose it to the heating gases or heating surfaces, such
as using a vertically revolving furnace or having special stirring mechanism or
special ventilating arrangements. Frequently, the more convenient arrangement for
utilising the waste pulverulent hydrated sulphate of lime, consists in compressing this
material into pieces of requisite size and then burning" these pieces or burning the
semi-pulverulent mass itself. The operation of "burning" can be done by means of
hot products of combustion, by hot air or otherwise, the temperature being regulated
so as not to frit the mass.
The operation is completed, when a sample withdrawn from the kiln after cooling,
pounding up if in lumps and mixing with water, hardens to the desired degree in a
few minutes.
THIS 30th day of September 1889.
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Patent Agents for the Applicants.
WM. P. THOMPSON & Co..
Of 6, Lord Street, Liverpool, Patent Agents for the Applicants.
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Plaster of Paris and in the
Utilisation of Waste or Cheap Materials therefor.
We, WILLIAM JOHN OSWALD, Cobridge, Stoke-on-Trent, Merchant, JOHN ROGERS
ASHWELL, F.I.C., F.C.S., 111 Waterloo Crescent, Nottingham, and JOHN ARTHUR
COOKE, 103 Waterloo Crescent, Nottingham, 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 the manufacture of plaster from old waste, plaster
moulds or casts, and other like waste or artificially prepared hydrated sulphate of
lime. Enormous quantities of these casts or moulds are at present thrown away as
useless when done with, or are simply used for whitening floors and the like. Further-
more, very large quantities of hydrated sulphate of lime, being either old plaster of
Paris which has lost its power of hardening, or even precipitates, or waste products of
chemical manufactories, can be utilised.

page_text: In carrying out our invention, the plaster moulds are broken up into small pieces
like macadam or finer, and, in the case of pulverulent hydrated sulphate of lime, the
material is preferably compressed into nodules or nuts. The small pieces and even
the pulverulent sulphate, if desired, are burned in ordinary kilns, but with revolving
stirring apparatus having stirrers or ploughs almost touching the bed of the furnace.
The temperature is kept at the requisite heat required to drive out part of the water of
combination, but not to dead burn the mass.
Any plaster barner can, from experience. regulate the heat within the requisite
limits, namely, such as will not permit the calcareous material to exceed a temperature
of 300 degrees Centrigrade, or sink during the operation below 95 degrees.
The operation of "burning" can be done by means of hot products of combustion,
by hot air or otherwise, the temperature being regulated so as not to frit the mass.
The operation is completed when a sample, withdrawn from the kiln after cooling,
pounding up, if in lumps, and mixing with water, hardens to the desired degree in a
few minutes.
By these means, old refuse plaster materials consisting of or containing gypsum,
which has lost its power of hardening or mixing with water, becomes re-endowed with
this property and the resultant plaster may be applied to any of its ordinary uses.
Further, the same plaster, after our treatment, may be used over and over again,
provided that after each hardening process it be treated as we describe.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what
we claim is-
The manufacture of plaster of Paris from waste or cheap materials such as described
by comminuting the same and roasting or caleining, at the requisite temperature,
substantially as described.
Dated this 30th day of June 1890.
WM. P. THOMPSON & Co.,
Of Liverpool, Manchester. and London, Patent Agents.