AN IMPROVED METHOD OF MANUFACTURING BRICKS AND SLABS IMPERVIOUS TO DAMP, FOR PREVENTING MOISTURE RISING IN PAVEMENTS AND THE WALLS IN HOUSES AND OTHER BUILDINGS
Year: 1861

page_text: LETTERS PATENT to William Charlton Forster, of No. 37, Gibson Street,
Lambeth, in the County of Surrey, Gentleman, for the Invention of
"AN IMPROVED METHOD OF MANUFACTURING BRICKS AND SLABS IMPERVIOUS TO
DAMP, FOR PREVENTING MOISTURE RISING IN PAVEMENTS AND THE WALLS
IN HOUSES AND OTHER BUILDINGS."
Sealed the 15th November 1861, and dated the 20th May 1861.
PROVISIONAL SPECIFICATION left by the said William Charlton Forster
at the Office of the Commissioners of Patents, with his Petition, on
the 20th May 1861.
I, WILLIAM CHARLTON FORSTER, of No. 37, Gibson Street, Lambeth, in
the County of Surrey, Gentleman, do hereby declare the nature of the said
Invention for "AN IMPROVED METHOD OF MANUFACTURING BRICKS AND SLABS
IMPERVIOUS TO DAMP, FOR PREVENTING MOISTURE RISING IN PAVEMENTS AND THE
WALLS IN HOUSES AND OTHER BUILDINGS," to be as follows, that is to say :-
The said bricks or slabs may be made of fire-clay, or earthenware clay,
or common clay prepared in the usual manner, with a proper admixture
of sand, or burnt clay, or powdered pottery ware, and the bricks or slabs
are to be made in separate halves in moulds of a proper form, size, and
depth, and for the purpose of rendering them impervious to damp,
according to the object of my Invention, I use one of the glazing mixtures
hereafter described, to be applied in the manner herein-after directed,
that is to say, first, I prepare a glazing mixture composed of two parts
of Cornish stone in fine powder (as it is usually sold), two parts of

page_text: powdered glass, one part of powdered barytes, and one part of china
clay or Devonshire clay (but for this mixture I prefer china clay); each
of the above ingredients is to be taken by measure. Second, another
form of glazing mixture consists of equal parts, by measure, of powdered
glass and powdered felspar. Third, another form of glazing mixture
consists of three parts, by measure, of powdered glass and one of china
clay or Devonshire clay. Fourth, another mixture is composed of twenty-
eight parts, by weight, of red lead, fourteen parts, by weight, of Cornish
stone, and two parts, by weight, of powdered glass. Fifth, I prepare
a mixture composed of one part, by measure, of the clay prepared for the
substance of the bricks or slabs, and from two to three parts of red lead.
The ingredients composing each of the above-described glazing
mixtures must be well incorporated together with water to the con-
sistence of cream, and laid on the upper surface of each of the halves
of the bricks or slabs with a brush when they have been moulded in
halves as aforesaid and dried. When the dried moulded halves have
been coated as aforesaid with one of the glazing mixtures above
described, I unite the two halves of the bricks or slabs, so that the
glazing mixture used may form the centre of each brick or slab. The
bricks or slabs are then to be burnt in the usual manner, and in burning
them a sufficient degree of heat must be applied to cause the glazing
mixture to become vitrified, when, by reason of such vitrification, the
bricks or slabs will become perfectly impervious to wet or damp.
The bricks or slabs made of fire-clay will require the greatest degree of
heat, and for those I recommend the use of the first, second, or third
glazing mixture above described.
For bricks or slabs made of earthenware clay, which require a less
degree of heat, I recommend the fourth glazing mixture above described.
And for those made of common brick earth, which require a still less
degree of heat, I recommend the use of the fifth glazing mixture above
described.
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 20th November 1861.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM 3
CHARLTON FORSTER, of No. 37, Gibson Street, Lambeth, in the County of
Surrey, Gentleman, send greeting.

page_text: WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twentieth day of May, in the year of our Lord
One thousand eight hundred and sixty-one, in the twenty-fourth 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 there-
after 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 METHOD OF MANUFACTURING BRICKS AND SLABS IMPERVIOUS TO
DAMP, FOR PREVENTING MOISTURE FROM RISING IN PAVEMENTS AND THE WALLS IN
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 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-
The said bricks or slabs may be made of fire-clay, earthenware clay, or
common clay, prepared in the usual manner of preparing it for bricks or
slabs, and they are to be made in separate halves, of a proper form, size,
and depth, according to the purpose to which they are to be applied, and
to prevent them from warping, and preserve them in their original shapes
during the process of drying. The upper surface of one half is to be
made with a projection, and the upper surface of the other half with a
corresponding depression or hollow, so that when both halves are united
they will form a perfect brick or slab. After the upper surfaces have
been allowed to dry for a few hours, the two halves should be fitted
together, placing the before-mentioned projection of one-half within
the before-mentioned depression or hollow in the other half, and then
dried in the ordinary way. When the bricks or slabs have been dried
and are ready for burning, the two halves of each brick or slab are to

page_text: be separated, and a coating of one of the glazing mixtures herein-after
described is to be applied to the upper surfaces herein-before mentioned
with a brush; they are then to be united and burnt in the ordinary
manner according to the kind of clay of which they are composed, when
the glazing mixture will become vitrified, and the bricks or slabs rendered
perfectly impervious to moisture, the process of absorption being arrested
by the internal glazing above described, and the outer surfaces still
remain unglazed and adhesive. The bricks and slabs may be made of
different shapes and sizes to suit the thickness and position of the walls,
and the purposes to which they are to be applied, and where the bricks
are required to be used to walls the sides of which adjoin to the earth,
they may be set edgewise, or they may be vitrified laterally, instead of
longitudinally, as above described, in which case the only alteration in
the
process
of manufacture would be in the shape of the moulds in which
they are made. To decrease the weight of the bricks, one of the halves
may be quite perforated with a number of holes vertically, which would
not interfere with their efficiency in preventing the rising or lateral
passage of damp, and will afford greater adhesion in building. The
glazing mixtures are to be composed of different materials according to
the clay used in manufacturing the bricks or slabs, and the degree of
heat to which they are to be exposed in burning, that is to say:-For
bricks or slabs made of fire-clay, either of the three mixtures next herein-
after described may be used. First, a mixture compounded of the
following ingredients:-I take two parts (by measure) of powdered
Cornish stone, two parts of powdered glass, one part of powdered barytes,
and one pait of china clay, or Devonshire clay in powder (but for this
mixture I prefer china clay), and I then thoroughly mix and incorporate
the above ingredients together with water to the consistence of cream,
when the mixture will be ready for application. Secondly, a mixture
compounded as follows:-One part (by measure) of powdered felspar,
and one part of powdered glass, to be mixed and incorporated as before
Tndly, the
() fundred for
and three parts of powdered glass, mixed and incorporated as before
described.
For bricks or slabs made of earthenware clay, I compound a glazing
mixture of the following materials, that is to say:-Twenty-eight parts
(by weight) of red lead, fourteen parts of powdered Cornish stone, and
two parts of powdered glass, mixed and incorporated as before described.
For bricks or slabs made of common clay, and which will not bear so

page_text: great a heat as either fire-clay or earthenware clay, I use a glazing mix-
ture composed of the following ingredients, that is to say:-One part (by
weight) of the same clay in powder of which the bricks are made, and
two or three parts of red lead, mixed and incorporated with water to
the consistence of cream, as before described.
The object of my Invention is to produce bricks or slabs glazed or
vitrified in the interior, and thereby to render them perfectly impervious
to damp, and at the same time by avoiding glazing the external surfaces
to preserve the adhesive properties of ordinary bricks or slabs. Thic
manner in which the bricks may be applied to prevent damp in houses
and buildings already erected, is by taking out one course of bricks near
the foundation, and substituting a course of my bricks or slabs set in
cement or mortar, which may be done without inconvenience to the
occupiers of inhabited houses, and also by placing between the walls of
the building and the adjoining earth a facing of the bricks or slabs from
the foundation to the surface of the earth surrounding the building.
Their applicability to new buildings, and the manner of using them is
obvious from the foregoing description. For the purpose of preventing
damp arising in floors of churches, kitchens, cellars, and underground
rooms, the slabs well set in cement or mortar will effectually prevent the
rising of damp or moisture, and they as well as the bricks may be used
for a similar purpose as a paving for stables and other outbuildings
where a strong pavement impervious to damp is required.
I claim as my Invention the application of glazing or vitrifying mixtures
to 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 here-
unto set my hand and seal, this Twentieth day of November, in
the year of our Lord One thousand eight hundred and sixty-one.
W. C. FORSTER. (L.S.)