AN IMPROVEMENT IN THE MANUFACTURE OF BRICKS AND SLABS FOR PREVENTING DAMP IN THE WALLS OF HOUSES AND OTHER BUILDINGS
Year: 1858

page_text: LETTERS PATENT to William Charlton Forster, of No. 6, Great Tower
Street, in the City of London, Gentleman, for the Invention of "AN
IMPROVEMENT IN THE MANUFACTURE OF BRICKS AND SLABS FOR PREVENTING
DAMP IN THE WALLS OF HOUSES AND OTHER BUILDINGS."
Sealed the 14th August 1858, and dated the 10th May 1858.
PROVISIONAL SPECIFICATION left by the said William Charlton Forster
at the Office of the Commissioners of Patents, with his Petition, on
the 10th May 1858.
I, WILLIAM CHARLTON FORSTER, of No. 6, Great Tower Street, in the
City of London, Gentleman, do hereby declare the nature of the said
Invention for "AN IMPROVEMENT IN THE MANUFACTURE OF BRICKS AND SLABS FOR
PREVENTING DAMP IN THE WALLS OF HOUSES AND OTHER BUILDINGS," to be as
follows:-
The said bricks or slabs are to be made of clay, or a mixture of about three
parts of clay and about one part of burnt clay or broken pottery roughly
powdered and well mixed; they are to be made in separate halves in moulds
as whole bricks or slabs are usually made. I then cover the upper surface of
one of the said halves to the thickness of about a quarter of an inch with a
mixture composed of about three parts of sand or powdered glass or powdered
flint and one part of lime well mixed with water to the consistence of mortar,

page_text: and I then unite the two halves of the said bricks or slabs, so that the mixture
above mentioned may form the centre of each brick. The bricks are then to
be dried and burnt in the usual way, and in burning them a sufficient degree
of heat must be applied to cause the above mentioned mixture to become
vitrified, when by reason of such vitrification the bricks or slabs will be
perfectly impervious to wet or damp. Where the clay used will not bear a
sufficient degree of heat for the above mixture to become vitrified, I
recommend the addition of some fusing or fluxing material to the above
mixture, such as soda, potash, saltpetre, alum, oxide of lead, oxide of tin or
borax. I also in the manufacture of such bricks or slabs adopt the plan of
making on one or more of the outer surfaces or ends thereof half holes or
hollows or grooves for the purpose of causing stronger adhesion with the
mortar or cement used in building with them.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Charlton Forster in the Great Seal Patent Office
on the 14th September 1858.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
CHARLTON FORSTER, of No. 6, Great Tower Street, in the City of London,
Gentleman, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Fourth day of May, in the year of our Lord One
thousand eight hundred and fifty-eight, in the twenty-first year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the
said William Charlton Forster, Her special licence that I, the said William
Charlton Forster, my executors, administrators, and assigns, or such others
as I, the said William Charlton Forster, 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 IMPROVEMENT IN THE MANUFACTURE OF BRICKS AND SLABS
FOR PREVENTING DAMP IN THE WALLS OF HOUSES AND OTHER BUILDINGS," upon
the condition (amongst others) that I, the said William Charlton Forster,
my executors 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

page_text: 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 William Charlton Forster, 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 said Invention consists of the production of a vitrified substance in the
interior of bricks or slabs, whereby the outer surfaces remain unglazed and
adhesive, and the absorption of water or damp from the lower surface to the
upper surface is prevented.
The mode of manufacturing the said bricks or slabs is as follows:-I take
clay prepared in the usual mode for manufacturing bricks, or a mixture
composed of about three parts of clay and about one part of burnt clay or
broken pottery roughly powdered, and well mixed. The prepared clay or
mixture is then to be moulded in separate halves, so that both shall when
united form bricks or slabs of the required size in the same manner that whole
bricks or slabs are now commonly made. I then use a vitrifying mixture
composed of about three equal parts of sand or powdered glass or powdered
flint and one equal part of lime, which substances are to be then well mixed
together with water to the consistence of mortar, and about the thickness of a
quarter of an inch of this mixture is to be applied to the upper surface of one
of the said halves. I then unite the said halves horizontally, so that the
vitrifying mixture may form the centre of each brick or slab. The bricks or
slabs are then to be dried and burnt in the usual manner, but in the burning
of them a sufficient degree of heat must be applied to cause the vitrifying
mixture above described to become melted or fused, when by reason of such
vitrification the object of my Invention will be attained by rendering the
bricks or slabs impervious to the complete absorption of wet or damp, as
above described. In the manufacture of the bricks or slabs above described
I have contemplated that the clay used shall be that commonly called fire-
clay, but where other clay is used which will not bear a sufficient degree of
heat to melt or fuse the vitrifying mixture, I recommend (to facilitate the
fusion) the addition to that mixture of a small proportion of some fluxing
material used in the manufacture of glass or enamel, such as soda, potash,
alum, oxide of lead, oxide of tin, borax, or clay, silicate of potass, silicate of
soda, or a liquid solution of silica or quartz or glass. In the manufacture of
my bricks or slabs I adopt the plan of making on one or, more of the outer
surfaces thereof half holes or hollows or grooves for the purpose of causing

page_text: stronger adhesion with the mortar or cement to be used in building with
them.
I claim as my Invention the application of a vitrifyed substance in the
interior of bricks or slabs for the purposes described in the title of my
Invention.
In witness whereof, I, the said William Charlton Forster, have hereunto
set my hand and seal, this Thirty-first day of August, in the year of
our Lord One thousand eight hundred and fifty-eight.
W. C. FORSTER. (L.S.)