Improvements in the Manufacture of Glazed Bricks and Tiles.
Year: 1889

page_text: Date of Application, 17th Sept., 1889
Complete Specification Left, 14th June, 1890-Accepted, 19th July., 1890
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Glazed Bricks and Tiles.
I, ALFRED JOHN CLAY, of Dresden, Stoke-on-Trent, in the County of Stafford,
Potter, do hereby declare the nature of this invention to be as follows:-
Attempts have at various times been made to manufacture glazed bricks and tiles
of soft clay such for example as that known as London clay but so far as I know
none of these attempts have resulted in the production from clay of this kind of
glazed bricks or tiles that could be relied upon for durability. One difficulty has
arisen from inability of the clay to withstand the amount of heat necessary to the
production of a glaze that would retain its hold upon the body of the brick.
Now in the manufacture according to my invention of bricks and tiles from clay
such as referred to the clay is ground with from 35 to 50 per cent. or thereabout of
silica in a mill to a powder suitable for brick inaking. The silica may be that due to
the presence of flint in the clay as found; or if the clay as found be without the
requisite amount of silica, I add the same or so much as is needful to make up the
proportion required.
The pulverized mixture of clay and silica can be made into unburnt bricks or tiles
of any desired form in any suitable manner; after which the surface or surfaces to be
glazed of each brick or tile has or have applied to it or them a thin preliminary
coating or dressing of a glazing compound that does not contain silica, and upon which
preliminary coating or dressing is superposed a coating of any known or suitable
compound to produce when burnt a white glaze such as heretofore has been produced
on bricks and tiles. A compound suitable for the preliminary coating or dressing
consists of 3 parts by weight of whito load two parts by weight of ground Cornish
stone, and one part by weight of Devonshire prepared potter's ball clay; the whole
well mixed with water to form a liquid.
The bricks or tiles having been coated where required with the preliminary coating
or dressing and also with the second or final coating or dressing of glaze
according to requirement, are fired it may be in the usual way of firing glazed
bricks.
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Glazed Bricks and Tiles.
I, ALFRED JOHN CLAY, late of Dresden, Stoke-on-Trent, in the County of Stafford,
and now of Chudleigh, Newton Abbott, in the County of Devon, Potter, do
hereby declare the nature of this 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 has reference to the manufacture of glazed bricks and tiles such as
are known in the trade as enamelled glazed bricks and tiles, and when hereinafter
referring to glazing or glaze, or using the expression "glazed" it is to be understood
that I mean that particular kind of glazing or glaze which is known in the trade as
enamelled glaze.
Attempts have at various times been made to manufacture glazed bricks and tiles
such as are known in the trade as enamelled glazed bricks and tiles of soft clay, such
for example as that known as London clay, and which is procurable in large quantities

page_text: in and around London, but, so far as I know, none of these attempts have resulted
in the production, from clay of this kind, of glazed bricks or tiles of the kind referred
to that could be relied upon for durability..
The principal difficulty has arisen from the fact that clay of this nature is not
sufficiently strong to withstand the amount of heat necessary to the production of
an enamel glaze that would retain its hold upon the body or face of the brick.
Now in the manufacture according to my invention of glazed bricks and tiles of the
kind mentioned above from clay such as referred to, the clay is ground, with a
suitable proportion say from fifteen per cent. by weight to thirty per cent. by weight,
or thereabout, of silica, in a suitable apparatus such as an ordinary mortar mill,
to a powder, and this powder is passed on to and through a clay pug and is
therein prepared with water in the ordinary way to a suitable condition for
making bricks.
The proportion of silica to be added will depend upon the proportion of silica
already present in the particular clay to be dealt with; and in order to ascertain
the percentage of silica it will be desirable to add to any particular kind of clay the
following plan can be adopted. A brick (or bricks) having been made from the
clay without adding silica and without glazing, is then subjected to heat in a
kiln at the same time there is placed into the same kiln, separately, but close to
the brick a small quantity (say a cubic inch) of the glazing compound ordinarily
employed in making glazed bricks. If the brick squats (as it is technically termed)
before the glazing compound, then the clay of which the brick is composed will
require more silica.
Tests are made by making successive bricks each with a larger proportion of silica
and testing these as against the glazing compound until the latter squats first. The
silica may in some instances be obtained from the rough flints which are procurable
with tlie clay in this case it would be necessary to reduce them to powder; to this
end it is advantageous to burn the flints in some suitable and cheap manner, for
example in clamps, in order to soften the flints and make them easier to pulverise;
in other cases it might be found cheaper to use silica obtained in a sandy forın such
as that in which it is obtainable in the neighbourhood of London; and which can be
blended with the clay at much less cost than silica obtained in the form of flints as
above mentioned.
The pulverised mixture of clay and silica can be made into unburnt bricks or tiles
of any desired form in any suitable manner; and when the same have been allowed
to become partially dry and to assume the state of dryness in which it is usual to
apply the glazing composition in the ordinary process of making enamelled glazed
bricks and tiles which condition is readily recognizable by a competent brick
maker as well understood, the surface or surfaces to be glazed, of each brick or tile,
has or have, applied to it or them, according to my invention a thin preliminary
coating or dressing of a glazing mixture and upon this preliminary coating or dressing
is or are superposed a coating or coatings of any known or suitable mixture to
produce, when burnt, a glaze such as heretofore has been produced on bricks and
tiles which may be white or of any desired color. A mixture suitable for the
preliminary coating or dressing consists of three parts by weight of white lead; two
parts by weight of ground Cornish stone; and one part by weight of Devonshire
prepared potters best.ball clay, the whole well mixed with water to form a liquid, and
care being taken not to allow the heavier substances to settle when using this mixture.
I have obtained good results by using the above substances in the proportions stated
with ten parts by weight of water. After dipping a number of bricks the proportion
of water in the mixture becomes reduced and water should be added to the mixture
to maintain the desired proportion.
The bricks or tiles having been coated where required with the preliminary coating
or dressing and also with a second one or more coatings or dressings of glazing
mixture according to requirement are fired in the usual way of firing enamelled
glazed bricks.

page_text: Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. The manufacture in the manner hereinabove described of glazed bricks and
tiles, using soft clay such as that known as London clay, with silica, in, or about in,
the proportions mentioned, a preliminary coating or dressing, and a glazing mixture
or substance as set forth.
2. In the manufacture of glazed bricks and tiles as set forth treating the unburnt
bricks or tiles with a preliminary coating or dressing of white lead, ground Cornish
stone, and Devonshire prepared potters hall clay mixed in or about in the propor-
tions indicated with a suitable quantity of water as set forth, preparatory to the
application of a glazing mixture or substance.
Dated this with day of June 1890
W. Lloyd Wise,
ALFRED J. CLAY.
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.