IMPROVEMENTS IN THE MANUFACTURE OF CEMENTS, ARTificial STONE, AND PLASTER OF PARIS
Year: 1873

page_text: LETTERS PATENT to the Reverend Granville Hamilton Forbes, of
Broughton Rectory, in the County of Northampton, for the Inven-
tion of "IMPROVEMENTS IN THE MANUFACTURE OF CEMENTS, ARTificial
STONE, AND PLASTER OF PARIS."
Scaled the 10th June 1873, and dated the 18th April 1873.
PROVISIONAL SPECIFICATION left by the said Reverend Granville
Hamilton Forbes at the Office of the Commissioners of Patents,
with his Petition, on the 18th April 1873.
I, the Reverend GRANVILLE HAMILTON FORBES, of Broughton
Rectory, in the County of Northampton, do hereby declare the nature
of the said Invention for "IMPROVEMENTS IN THE MANUFACTURE OF CEMENTS,
ARTIFICIAL STONE, AND PLASTER OF PARIS," to be as follows:-
My Invention consists in mixing tar, pitch, or bitumen with the
substances usually employed to make Portland, Roman, Parian, and
other cements, which when the compound is burnt gives great additional
strength and durability to the product.

page_text: -
In carrying out the said Invention I proceed as follows :-
1. I make an improved Portland cement by taking from 65 to 75 per
cent. of chalk or limestone and from 25 to 35 per cent. of any
clay
containing the necessary quantity of silica and alumina and oxide of iron,
and soda or magnesia. (I prefer the clay to have these ingredients in
the following proportions:-Silica, 68.45; alumina, 11.64; oxide of iron,
14; soda, 4.) I reduce the chalk or limestone and the clay to powder,
and to this I add sufficient tar, pitch, or similar bituminous substance
(or a combination of any or all of them) to unite the whole when
thoroughly mixed and kneaded into a compact cohesive mass, which is
then burnt and reduced to powder, when it is capable of being used as
an excellent cement by mixing with water in the usual manner.
Instead of the chalk and clay I may use any natural clay or marl or
rock which contains all or most of the constituents of the chalk and clay
combined, such as the clay obtained from one of the layers of the
Kimmeridge clay found at Boulogne, in France, used for making natural
Portland cement or any natural clay or rock of a similar or nearly
similar analytical value, such as the best blue lias, varieties of limestone
found in England.
2. I make an improved Roman cement in the same way by using
instead of the former clay any one of the natural clays or cement stones
employed in England and America and elsewhere to make Roman
cement, such as the clay found in Kent and Essex, in Yorkshire, in
the Isle of Wight, in North Wales, and Staffordshire, and other parts of
England; and at Calderwood, in Scotland; and also to a very large extent
in the United States of America, such as that obtained at Utica, Illinois ;
at Sandusky, Ohio; at Cumberland, Maryland; at Shepherds' Town,
Virginia; at the Hill Falls, Ulster, New York; and other places in the
States and elsewhere, as at Theil, in France. The characteristic of such
stones is that they contain a large proportion of carbonate of lime (or
in some cases lime) in addition to alumina, silica, magnesia, and oxide
of iron in varying proportions. I prefer those which contain not less
than 40 per cent. of carbonate of lime. In those cases where the stone
or clay is deficient in carbonate of lime I add the necessary quantity of
chalk or limestone. I reduce the above specified materials to powder,
and mix with it a sufficient quantity of tar or pitch or similar bituminous
substance, or a combination of any or all of them, to unite the whole

page_text: compound when thoroughly mixed and kneaded into a compact cohesive
mass, which is thoroughly burnt and afterwards reduced to a fine
powder by crushing. It is then mixed with water in the usual way
that the ordinary Roman cement is mixed when used.
3. I make an improved artificial puzzolana cement by using any one of
such natural clays as are usually employed in making artificial puzzolana.
With this clay I mix chalk or limestone, and tar or pitch, or similar
bituminous substance or a combination of any or of all them. The
proportion of chalk used is such as to give (after the thorough com-
bustion of the whole compound) from one to two parts of lime or a
sulphate of lime to three parts of artificial puzzolana. The quantity of
the tar or pitch, or bitumen is determined in the same manner as in
the making of previous cements, Nos. 1 and 2.
.
Instead of the clay I may use natural puzzolana or any similar
volcanic product, such as gneiss or santorin carth, or trap, or trachyt,
or trachytic porphyry, or any volcanic rock or product which
contains the necessary quantity of silica and alumina; but in selecting
these volcanic products it is necessary to choose those which gain in
cementitious value by being burned. The compound is burnt and after-
wards reduced to powder.
In some cases a small quantity of naphtha or vegetable or animal oil
or fat or fatty matter, or a combination of naphtha and vegetable or
animal oil or fat or fatty matter, or a combination of naphtha and
vegetable or animal oil or fat or fatty matter with petroleum or other
mineral oil, may be used to improve each of the three cements described
above, as Portland, Roman, & artificial puzzolana. These oils are
mixed with compound before burning, and their effect is to make a
finer quality of cement.
The cements above described are well adapted to use as artificial
stone or as substitutes for plaster of Paris.
4. I make an improved plaster of Paris by mixing chalk or limestone
with tar or pitch or similar bituminous substance, or a combination of
any or all of them, in the proportion of about one-fourth or one-fifth of
tar or pitch or bitumen to the chalk or limestone. After thorough
mixing and kneading the compound is burnt and afterwards reduced to
powder. A little naphtha added before burning gives greater strength

page_text: to the product. The same principle of using tar or pitch or any similar
bituminous substance may be advantageously applied to the manu-
facture of all cements, artificial stone, and plaster which are produced
by burning chalk or limestone in combination with any cement, clays,
or stones.
to the product. The same principle of using tar or pitch or any similar
bituminous substance may be advantageously applied to the manu-
facture of all cements, artificial stone, and plaster which are produced
by burning chalk or limestone in combination with any cement, clays,
or stones.
The advantage of my Invention is not only in improving the quality
of the cements but also in making the burning of the substances from
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Reverend Granville Hamilton Forbes in the Great
Scal Patent Office on the 18th October 1873.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, the
Reverend GRANVILLE HAMILTON FORBES, of Broughton Rectory, in the
County of Northampton, send grecting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Eighteenth day of April, in the year
of our Lord One thousand eight hundred and seventy-three, in the
thirty-sixth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Granville Hamilton Forbes, Her
special licence that I, the said Granville Hamilton Forbes, my executors,
administrators, and assigns, or such others as I, the said Granville
Hamilton Forbes, 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, usc, 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 CEMENTS, ARTIFICIAL
STONE, AND PLASTER OF PARIS," upon the condition (amongst others) that
I, the said Granville Hamilton Forbes, my exccutors or administrators,
by an instrument in writing under my, or their, or one of their hands
and seals, 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 Scal Patent Office within

page_text: .
six calendar months next and immediately after the date of the said
Letters Patent.
NOW KNOW YE, that I, the said Granville Hamilton Forbes, 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:-
My Invention consists in mixing tar, pitch, or bitumen, or other
hercin-mentioned substances with the substances usually employed to
make Portland, Roman, Parian, and other cements, which, when the
compound is burnt, gives great additional strength and durability to
the product.
Thus far I have briefly described the nature and object of my
said Invention; and I will now, in compliance with the aforesaid con-
dition contained in the said Letters Patent to me granted, proceed to
more fully exemplify the nature of my said Invention. so as together
with the foregoing statements to particularly describe and ascertain the
nature of my said Invention, and in what manner the same is to be
performed or carried out in practice, that is to say :-
I proceed as follows:-I mix coal tar, or wood tar, or peat tar, or
mineral tar, or pitch or other similar bituminous substance (or a com-
bination of any or all of them) with the substances usually employed
to make Portland, Roman, Parian, and other cements and plaster..
In some cases I combine with the above-named substances naphtha or
petroleum, or other similar oil, or vegetable or animal oil, or fat or fatty
matter (or a combination of any or all of them).
According to the first part of my Invention, namely, that which
relates to the combination of the substances usually employed to make
Portland cement with the tar, pitch, or similar bituminous substance
before specified, I take from sixty-five to seventy-five per cent. of chalk
and from twenty-five to thirty-five per cent. of any clay containing the
necessary quantity of silica and alumina, and oxide of iron and soda or
magnesia for my purpose. I grind the chalk and clay together in a
mortar mill, and add sufficient water to mix the whole thoroughly.
After being taken from the mill the compound is allowed to dry suffi-
ciently to form it into blocks or pieces, which are thon baked in an oven
(or in any other convenient manner) at a high temperature. It is
afterwards ground again, and mixed thoroughly in the mill with abouť.

page_text: one-third of its weight of coal tar, wood tar, peat tar, mineral tar, pitch,
or similar bituminous matter. It is then taken from the mill, and
pressed either by hand or machinery into blocks or balls of any con-
venient shape or size or it may be pressed by the action of the mill,
and cut out of the pan in pieces; but I prefer to use a press for the
purpose.
Instead of grinding the compound a second time, as above described,
I sometimes adopt the following method of combining it with the tar or
pitch, or similar bituminous matter:-After the blocks or pieces have
been sufficiently dried I heat them (in an oven or in any other con-
venient manner) to the highest point of temperature short of ignition.
They are then put at once into the tar or pitch or similar bituminous
matter, and allowed to remain in it until they have absorbed enough of
the liquid for my purpose. I sometimes heat the blocks or pieces red
hot, and put them into the tar or similar bituminous substance in that
state.
I sometimes use instead of the chalk and clay any natural clay or rock,
which contains all, or nearly all, of the constituents of the chalk and
clay combined. I combine the clay or rock with the same proportion
of the tar or similar bituminous substance, before specified, cither by
making it red hot, and plunging it at once into the tar or other similar
bituminous substance, where I allow it to remain until it has absorbed
enough of the liquid for my purpose, or I grind the clay or stone with
the tar or other bituminous substance in the mill, and afterwards form it
into block or balls, as before described.
According to the second part of my Invention I use instead of the
chalk and clay (or clay and stone) any of the clays or natural cement
stones employed in England and America, and elsewhere, to make
Roman cement.
I proceed in the same manner as before described, combining the clay
or stone with the tar or pitch, or similar bituminous substance (or a
combination of any or all of them), by either of the methods before
specified, namely, by grinding the clay or stone in a mortar mill with
the same proportion of the tar or pitch, or similar bituminous substance
above specified, or I heat the clay or stone red hot without previously
grinding it, and put it into the tar or other similar bituminous sub-

page_text: stance, as ADSVIN sumie of the L
my purpose.
According to the third part of my Invention I use any one of such
natural clays as are usually employed in making artificial puzzolana.
With this clay I mix (by either of the methods herein-before described)
chalk or limestone, and the tar or pitch, or similar bituminous substance
before specified, or a combination of any or all of them. The proportion
of chalk is such as to give (after the thorough combustion of the whole
compound) from one to two parts of lime or a sulphate of lime to three
parts of artificial puzzolana. The proportion of the tar, pitch, or
bitumen is the same as above described.
Instead of the clay I may use natural puzzolana, or any similar
volcanic product, or any volcanic rock or product which contains the
necessary quantity of silica and alumina. But in selecting these volcanic
products it is necessary to choose those which gain in cementitious
value by being burned.
According to the fourth part of my Invention I make use of sulphate
of lime in combination with chalk and the tar, pitch, or other similar
bituminous substance (or a combination of any or all of them). I take
from ten to twenty per cent. of sulphate of lime, and from eighty to
ninety per cent. of chalk or limestone. I mix these intimately by
grinding them together with water in a mortar mill, and afterwards dry
and bake them in the manner before described. The blocks or balls are
then mixed with tar, pitch, or other similar bituminous substance, or a
combination of any or all of them by either of the methods beforc
described, the proportion of the tar or other similar bituminous sub-
stance or substances being the same as above described.
;
According to the fifth part of my Invention I combine with the
materials last specified a small quantity of alum and borax in the pro-
portion commonly used to make Parian cement, and preceed in the
manner above described.
Sixth. In some cases I use a small quantity of naphtha or petroleum,
or other similar oil, or vegetable or animal oil, fat or fatty matter, or a
combination of naphtha and vegetable or animal oil, or fat or fatty
matter with petroleum or other similar oil to improve each of the com-
pounds described under the first, second, third, fourth, and fifth heads of

page_text: this Specification. These oils are mixed with the tar or other similar
bituminous substance before it is combined with the other ingredients,
the proportion being from one half pint to two pints of the oil or oils to
one hundredweight of any of the compounds.
Having now particularly described and ascertained the nature and 5
object of my Invention, and in what manner the same is to be per-
formed or put in practice, I hereby declare that I claim,-
First. The use of coal tar, wood tar, peat tar, mineral tar, or pitch, or
other similar bituminous matter (or a mixture of any combination or all
of them) in combination with the substances mentioned in this Specifi- 1
cation for the purposes aforesaid.
Secondly. The use of vegetable or animal oil, or fat or fatty matter
(or a mixture of any or all of them) in combination with the several
compounds above specified for the purposes aforesaid.
Thirdly. The use of naphtha or petroleum, or other similar oil (or a 1
mixture of any or all of them) in combination with the other sub-
stances mentioned in this Specification for the purposes aforesaid.
In witness whereof, I, the said Granville Hamilton Forbés, have
hereunto set my hand and seal, this Fifteenth day of October
in the year of our Lord One thousand eight hundred and seventy- 2
threc.
GRANVILLE HAMILTON FORBES. (L.s.)
Witness,
HENRY JAMES,
Vicar of Cransby,
Northampton.