IMPROVEMENTS IN THE MANUFACTURE OF CEMENT
Year: 1875

page_text: LETTERS PATENT to John Thomlinson, of Armathwaite Castle, near
Carlisle, in the County of Cumberland, Merchant, and John
Salkeld, of 34, Junction Road, London, in the County of Middlesex,
Cement Manufacturer, for the Invention of "IMPROVEMENTS IN THE
MANUFACTURE OF CEMENT."
Sealed the 26th May 1876, and dated the 6th December 1875.
PROVISIONAL SPECIFICATION left by the said John Thomlinson and
John Salkeld at the Office of the Commissioners of Patents, with
their Petition, on the 6th December 1875.
We, JOHN THOMLINSON, of Armathwaite Castle, near Carlisle, in the
County of Cumberland, Merchant, and JOHN SALKELD, of 34, Junction
Road, London, in the County of Middlesex, Cement Manufacturer,
do hereby declare the nature of the said Invention for "IMPROVEMENTS
IN THE MANUFActure of CemenT," to be as follows:
This Invention has for its object improvements in the manufacture
of cement.

page_text: In the Specification of a Patent granted to John Thomlinson, and
dated 22nd November, 1869, No. 3373, a process for the manufacture of
cement is described, consisting in burning gypsum at a high temperature,
grinding it and mixing it with powdered alum or borax. This manu-
facture has not been successful, and we have ascertained that the causes
of failure are,—
Firstly. That the gypsum has been allowed to be in contact with the
fuel during the process of burning, which has caused the cement when
used to emit an offensive odour.]
Secondly. That the gypsum and alum wore ground together with
horizontal millstones; this was done for the purpose of mixing the alum
and gypsum together, and to assist in reducing the alum into a finer
powder than could be attained by grinding the alum apart from the
gypsum; but in thus grinding the gypsum was overground, and
therefore when it was made wet for use as a cement it was found to be
sticky or glutinous and difficult in application, owing to its adhesion to
the tools used in working it.
Thirdly. That alum only was used along with the gypsum, and the
alum was not of suitable quality and was not reduced to a sufficiently
fine powder.
According to our Invention we employ gypsum calcined in an oven
or kiln, in which the fuel is burnt on fire-grates apart from the material
in the body of the oven or kiln.
The oven or kiln we employ is in the form of a beehive, and flues in
the walls of the oven or kiln lead the heat and products of combustion
from the fires nearly to the top of the interior of the oven or kiln,
whence they descend amongst the materials to flues beneath the bottom
which lead into a chimney.
The burning is carried on until the whole contents of the oven or
kiln are at a full red heat. After burning the lumps of gypsum are
romoved from the oven or kiln, their surfaces are brushed to remove the
dust, then they are not ground but crushed in order to retain to the
gypsum its strength in the form of splinters or crystals; it is afterwards
sieved through sieves calculated to produce the coarse as well as the
finer qualities of cement. The alum should be potash alum. We employ :
borax and tartar as well as alum. The alum, borax, or tartar, we reduce

page_text: to a powder, and dress the same through silk or lawn sieves with 70 to
100 meshes to an inch; the powders are mixed in a dry state. The
proportion (whether of one of the salts or of a combination of the whole
or of two) to the burnt gypsum is very small, say about three per cent.
To produce colored or tinted cements we add finely powdered pigments,
which have also been sieved to the sieved alum, or borax and tartar,
and again pass them through a coarse sieve to thoroughly mix them, or
the pigments may be crushed together with the gypsum.
M 1:1
Holla San hunning onsum
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said John Thomlinson and John Salkeld in the Great
Seal Patent Office on the 6th June 1876.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, JOHN
THOMLINSON, of Armathwaite Castle, near Carlisle, in the County of
Cumberland, Merchant, and JOHN SALKELD, of 34, Junction Road,
London, in the County of Middlesex, Cement Manufacturer, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Sixth day of December, in the
year of our Lord One thousand eight hundred and seventy-five, in the
thirty-ninth year of Her reign, did for Herself, Her heirs and suc-
cessors, give and grant unto us, the said John Thomlinson and John
Salkeld, Her special license, that we, the said John Thomlinson and
John Salkeld, my executors, administrators, and assigns, or such others
as we, the said John Thomlinson and John Salkeld, our 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 "IMPROVEMENTS
IN THE MANUFACTURE OF CEMENT," upon the condition (amongst others)
that we, the said John Thomlinson and John Salkeld, our executors
or administrators, by an instrument in writing under our or their

page_text: bands and seals, or under the hand and seal of one of us or them,
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 John Salkeld, on behalf of myself.
and the said John Thomlinson, do hereby declare the nature of the
said Invention, and in what manner the same is to be performed,
to be particularly described and ascertained in and by the following 1
statement thereof, that is to say:-
-
This Invention has for its object improvements in the manufacture
of cement.
In the Specification of a Patent granted to John Thomlinson, and
dated 22nd November, 1869, No. 3373, a process for the manufacture of 1
cement is described, consisting in burning gypsum at a high tem-
perature, grinding it, and mixing it with powdered alum or borax.
This manufacture has not been successful, and we have ascertained that
the causes of failure are,-
-
Firstly. That the gypsum has been allowed to be in contact with the 2
fuel during the process of burning, which has caused the cement when
used to emit an offensive odour.
Secondly. That the gypsum and alum were ground together with
horizontal millstones, this was done for the purpose of mixing the alum
and gypsum together, and to assist in reducing the alum into a finer 2
powder than could be attained by grinding the alum apart from the
gypsum; but in thus grinding the gypsum was overground, and
therefore when it was made wet for use as a cement it was found to be
sticky or glutinous and difficult in application owing to its adhesion to
the tools used in working it.
Thirdly. That alum only was used along with the gypsum, and the
alum was not of suitable quality and was not reduced to a sufficiently
fine powder.
3
According to our Invention we employ gypsum calcined in an oven
or kiln, in which the fuel is burnt on fire-grates apart from the material 3
in the body of the oven or kiln,

page_text: The burning is carried on until the whole contents of the oven or
kiln are at a full red heat. After burning the lumps of gypsum are
removed from the oven or kiln, their surfaces are brushed to remove
the dust, then they are broken and any colored pieces are picked out.
The burnt gypsum is afterwards crushed with edge runners and finally
it is sieved through sieves calculated to produce the coarse as well as
the finer qualities of cement. For the coarsest qualities we use rotating
wire gauze sieves of 45 meshes to the linear inch. For finer qualities
we use finer sieves, and for the finest we use silk sieves of 160 to the
inch. We mix the gypsum thus prepared with alum. The alum should
be potash alum. We employ borax and tartar as well as alum. The
alum, borax, or tartar, we reduce to a powder, and dress the same
through wire, silk, lawn, or other sieves, with 70 to 100 or more meshes
to an inch, indeed the finer the better. The powders are mixed in a
dry state. The proportion (whether of one of the salts or of a com-
bination of the whole or of two) to the burnt gypsum is very small, say
about three per cent. or less. When the salt is sifted very fine we have
found as little 7 lbs. to 4 hundredweight of gypsum succeed where rapid
setting is not required. We use borax when slow setting is required, a
cement made with alum and one-sixth of borax will remain workable for
two or three hours.
To produce colored or tinted cements we add finely powdered pig-
ments, which have also been sieved to the sieved alum or borax and
tartar, and again pass them through a coarse sieve to thoroughly mix
them, or the pigments may be crushed together with the gypsum.
The oven or kiln which we prefer to employ is shewn by the annexed
Drawings, no claim is made in respect to it; under our present Patent
it forms the subject of a separate application filed on the 6th day of
June, 1876.
Figures 1 and 2 of the annexed Drawings are vertical sections; and
Figure 3 is a horizontal section of the oven or kiln.
a, a, a, a, are four fire-places, from each of which a flue passes and
leads into the domed interior or body c of the oven or kiln; d is a
grating of iron bars, through which and through openings d' the heated
products of combustion after rising to the top descend, and then pass
by flues e into the spaces f between the walls g and the outer lining h.
A portion of the heat from the fires can also be allowed to pass direct

page_text: into the spaces when desired. The spaces fare gathered up at the top
into four chimnies i, i; k, k¹, k³, are dampers to regulate the draft.
Thus it will be seen that in addition to the interior or body c, the
spaces 1, 1, between the outer and inner linings are heated, and in these
spaces the raw gypsum is placed and here it is roasted till it becomes t
plaster of Paris; in this state it is drawn out by the openings 1, ", at the
bottom. So much of the plaster as is required for the manufacture of
our cement is returned to the oven or kiln, and placed in the interior
or body c, where it is exposed to a full red heat which is retained
until every trace of vapour passing away from the material has ceased. 1
Usually the material remains about 12 hours in the spaces 2 to
burn to plaster of Paris, and 24 hours in the interior or body c to render
it fit for the manufacture of cement; m, m, are charging doors at the
top; they can be closed air-tight; n is a cover which is removed to fill
the interior or body; o is a door which is opened to draw the charge ]
from the interior or body; and p is a door which is opened to remove
dust from beneath the grating & and to clear the passages.
The kiln or oven above described is applicable for burning gypsum,
which has been treated with solutions of alum or borax and tartar.
We claim the manufacture of cement from gypsum, burnt at a high a
heat and out of contact with the fuel, such gypsum being crushed and
passed through sieves to bring it to an uniform degree of fineness, and
then mixed with very finely powdered and sifted alum, borax, or tartar,
substantially as described.
In witness whereof, I, the said John Salkeld, have bereunto set
my hand and seal, this Sixth day of June, in the year of our Lord
One thousand eight hundred and seventy-six.