AN IMPROVED CEMENT APPLICABLE AS A PLASTER OR FOR MOULDING PURPOSES
Year: 1854

page_text: LETTERS PATENT to Henry Young Darracott Scott, of Queen's Terrace,
Woolwich, in the County of Kent, Captain in the Royal Engineers, for
the Invention of "AN IMPROVED CEMENT APPLICABLE AS A PLASTER OR FOR
MOULDING PURPOSES."
Sealed the 3rd November 1854, and dated the 13th May 1854.
PROVISIONAL SPECIFICATION left by the said Henry Young Darracott
Scott at the Office of the Commissioners of Patents, with his Petition,
on the 13th May 1854.
I, HENRY YOUNG DARRACOTT SCOTT, of Queen's Terrace, Woolwich, in the
County of Kent, Captain in the Royal Engineers, do hereby declare the nature
of the said Invention for "AN IMPROVED CEMENT APPLICABLE AS A PLASTER OR
FOR MOULDING PURPOSES" to be as follows:
My Invention consists in the adoption of the following process for the
manufacture of cement:-I subject limestones (in which term I include chalk
and what are termed hydraulic limestones), after they have been burned to
lime, to a further heating in contact with the products of combustion of coal,
coke, and substances of a like nature.
Now, whereas the lime produced from the purer and weak hydraulic lime-
stones by the simple burning hitherto practised sets only after the lapse of a
considerable time, or forms a friable mass, the same substance, after having
been subjected to the further treatment I propose, will, when ground to a
powder, and mixed with water in quantity sufficient to form a paste, set
somewhat after the manner of plaster of Paris, and even under water attain
quickly a considerable degree of hardness.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Henry. Young Darracott Scott in the Great Seal Patent
Office on the 13th November 1854.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, HENRY
YOUNG DARRACOTT SCOTT, of Queen's Terrace, Woolwich, in the County of
Kent, Captain in the Royal Engineers, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Thirteenth day of May, in the year of our Lord
One thousand eight hundred and fifty-four, in the seventeenth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me;
the said Henry Young Darrácott Scott, Her special licence, that I, the
said Henry Young Darracott Scott, my executors, administrators, and assigns,
or such others as I, the said Henry Young Darracott Scott, my executors,
• administrators, and assigns, should at any time agree with, and no others,
from time to time and at all times thereafter during the term therein
expressed, should and lawfully might make, use, exercise, and vend, within
the United. Kingdom of Great Britain and Ireland, the Channel Islands,
and Isle of Man, an Invention for "AN IMPROVED CEMENT APPLICABLE AS A
PLASTER OR FOR MOULDING PURPOSES," upon the condition (amongst others) that
I, the. said Henry Young. Darracott Scott, by an instrument in writing under
my hand and seal, should particularly describe and ascertain the nature of the
said Invention, and in what manner the same was to be performed, and cause
the same to be filed in the Great Seal Patent Office within six calendar
months next and immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Henry Young Darracott Scott, do
hereby declare the nature of my said Invention, and in what manner the
same is to be performed, to be particularly described and ascertained in and]
by the following statement (that is to say)
...My Invention of "An Improved Cement applicable as a Plaster or for
Moulding Purposés" has for its object the production from chalk or limestone
of a cement or plaster which will set somewhat after the manner of plaster of
Paris, but will attain a much greater degree of hardness, and when manipulation
is required will allow more, time to the operator to work to a surface, and
moreover will not be liable to injury from damp or rain.
My improved process for the manufacture of cement consists in subjecting
limestones (in which term I include chalk and what are termed hydraulic
limestones, after they have been burned to lime,) to a further heating in

page_text: contact with the products of combustion of coal, coke, and substances of a
like nature.
Now, whereas the lime produced from the purer and weak hydraulic lime-
stones by the simple burning hitherto practised sets only. after the lapse of a
considerable time, or forms a friable mass, the same substance, after having
been subjected to the further treatment I propose, will, when ground to a
powder, and mixed with water in quantity sufficient to form a paste, set
somewhat after the manner of plaster of Paris, and even under water attain
quickly a considerable degree of hardness.
I carry out my Invention in the following manner :-I first burn the chalk
or limestone in a kiln, and thereby produce quick-lime by any of the methods
ordinarily practised; after which I subject the quick-lime to a second heating,
at a dull red heat, in the presence of an atmosphere created by the combustion.
of carbonaceous fuel.
A convenient mode of doing this is to make use of a kiln of a reverberatory.
form, with the fuel arranged on bars at its bottom, and the previously calcined.
quick-lime placed at a short distance from it; this distance and the draught
being so arranged, that when the fuel is undergoing combustion the lime may
not be heated too highly, but yet sufficiently to take the appearance of a dull
cherry red. Should the heat maintained be too great the lime will remain. in
the ordinary state of quick-lime; or if it has previously acquired the property
of setting, as above described, and then the heat be urged too far, it will again.
lose it also, if the lime shew no sign of incandescence the process will be
quite ineffective for the purpose intended; unless, therefore, care be taken that
the temperature to be maintained during the second heating operation be
neither too high nor too low, the lime will, when made into a paste with
water, still behave in the ordinary manner of common quick-lime (that is to say),
instead of hardening into a solid coherent mass, it will either fall to a powder,
or, if mixed with more water than is sufficient to convert it into a hydrate, it
will dry up into a shrivelled cracked mass. Instead also of solidifying when
immersed in a pasty state in water, as is the case when it has undergone
the above-described process in a proper manner, it will quickly fall abroad.
This heating of the lime in the presence of an atmosphere derived from the
burning fue! I continue for twelve hours, more or less. I find that when when
working on a small scale, and where the supply of fuel is comparatively
unlimited, the necessary change may be effected in five or six hours, or.
even less.
Although my process, as will appear from the foregoing, is chiefly applicable to
limes prepared from chalk or the ordinary purer-limestones, I do not confine

page_text: myself to these. Limes possessing weak or moderate hydraulic properties may
thus be converted into cement, much better suited for many purposes than
when in their ordinary state. When, however, these properties become so
developed as to set quickly when burned in the ordinary manner, it is obvious
it would be useless to adopt a more expensive one.
The prepared lime when removed from the kiln will usually be found to have
reabsorbed a small amount of carbonic acid.
4
The pieces of lime to be operated upon may be of Macadam size. I have
sometimes found that when the pieces have been too large, the whole of the
lime has not been acted upon to the same extent. When removed from the
kiln, the lime is reduced to a powder, and packed in air-tight casks for the
market. A similar effect to that above described may likewise be produced
in an ordinary lime kiln, the limestone being converted into quick-lime and
then subjected to the foregoing second heating process in one continuous
operation. I find, however, this mode of effecting the desired change to be
very precarious and attended with great difficulty. When it is attempted, the
quantity of fuel must be greater than in ordinary lime burning; and as soon
as the conversion into quick-lime has been accomplished, the temperature must
be reduced by a proper regulation of the draught so as to comply with the
above specified conditions.
In using the cement care must be taken to wet the surface to which adhesion
is required to be made, and it is advisable even to rub into it some of the stuff
thinly mixed before laying on the mass.
The cement when set should be wetted at intervals during the first day.
Ornamental castings may be immersed in water for a few minutes after the
cement has solidified, and care should be taken that the thickness of a coating
be no greater than necessary, as the tendency to heating, after it is made up,
though greatly modified, is not entirely destroyed, and this property, when the
cement is in bulk, might endanger its safety.
When used as a plaster it may be mixed with a proportion of chalk in the
ground state; it will not then give so strong a resistance to a transverse
strain, but may still be worked to an excessively hard and well-polished
surface.
When used externally or as a pavement it may be washed over with a solu-
tion of silicate of potash or soda, as this increases the hardness of the surface
and renders it more impervious.
Coloring matter may be mixed with the cement, and when used as á
plaster this will prove very advantageous, as the cement will not be injured
by wasbing, but, on the contrary, will be improved by it.

page_text: This improved cement is admirably adapted for scagliola work, and imita-
tion marble, &c., as it is susceptible of a fine polish, and to the touch is similar
to the natural stone.
Having now described my Invention, and the manner of carrying the same
into effect, I wish it to be understood that under the above in part recited
Letters Patent I claim the preparation of a cement or plaster from chalk or
limestone, by subjecting it, when reduced to the state of quick-lime, to a dull
red heat in an atmosphere created by the combustion of carbonaceous fuels,
such as coke, culm, or other similar materials.
In witness whereof, I, the said Henry Young Darracott Scott, have
hereunto set my hand and seal, the Eleventh day of November, in the
year of our Lord One thousand eight hundred and fifty-four.
HENRY Y. D. SCOTT. (L.S.)