IMPROVEMENTS IN THE TREATMENT OF EARTHY CLAYS 'TO RENDER THEM BETTER ADAPTED FOR THE MANUFACTURE OF BRICKS
Year: 1878

page_text: LETTERS PATENT to Robert Pickwell, of Hull, Yorkshire, for the Invention
of "IMPROVEMENTS IN THE TREATMENT OF EARTHY CLAYS 'TO RENDER THEM
BETTER ADAPTED FOR THE MANUFACTURE OF BRICKS."
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Sealed the 4th March 1879. and dated the 9th September 1878.
17.
PROVISIONAL SPECIFICATION left by the said Robert Pickwell at the
Office of the Commissioners of Patents on the 9th September 1878.
ROBERT PICKWELL, of Hull, Yorkshire. "IMPROVEMENTS IN THE TREATMENT OF
EARTHY CLAYS TO RENDER THEM BETTER ADAPTED FOR THE MANUFACTURE OF
BRICKS."
This Invention relates to the treatment of clay or brick earth, and combining
therewith certain other mineral, earthy, or gaseous substances in such manner and
proportions as to admit of the production of bricks of any desired tint or colour
from red to white.
"
The clay from which bricks are ordinarily made assumes a red colour on being
burnt, and it is desirable in very many cases to be able to produce at will bricks
of a white, a grey, or other agreeable tint from such aforesaid red clays.
I accomplish this object by mixing with the clay one, or more, or all of the
following substances, namely
Carbonate of lime,"
"silica,"
"slacked lime,"
magnesia, or other generally similar and suitable mineral substance, or gas
resulting therefrom. The proper proportion of each ingredient is predetermined by
experimental trials in the analytical laboratory so that the clay when mixed in
large quantities shall be composed of the same (or nearly so) chemical composition,
as natural white or other clay, and when burnt shall produce bricks of the desired
white colour. Bricks of any other desired tint may also be produced by the addition
of suitable colouring materials..
"
The substances so compounded are prepared in either a plastic or semi-dry state
so as to produce either plastic moulded or "dry," or "semi-dry pressed bricks ;
that is to say, either moulded by hand or formed by pressure in suitably constructed
machines.
In this way the manufacture of plastic or other red brick clay into "slop" or
"semi-dry" bricks of a "white or other tint may be carried on, and this may be
done throughout the year, which cannot otherwise be done with many natural red,
plastic, or other clays.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Robert Pickwell in the Great Seal Patent Office on the 7th March
1879.
ROBERT PICKWELL, of Hull, Yorkshire. "IMPROVEMENTS IN THE TREATMENT OF
EARTHY CLAYS TO RENDER THEM BETTER ADAPTED FOR THE MANUFACTURE OF
BRICKS."
This Invention provides the means of making white bricks from clays or brick
earths that would otherwise burn of a red or other colour, varying from red to a
whitish tint, and for improving or perfecting the colour of clays or earths which
would naturally produce bricks of a whitish tint on being burnt.
It is well known that some brickmakers have for years mixed ground chalk and
water with their clays or earths in the manufacture of yellow or buff bricks, but
the inevitable natural result of this addition of ground chalk and water to the clays
or earths is to seriously damage the ultimate durability of the brick after it is burnt
and subjected to the deleterious effect of damp from the atmosphere, owing to the
chalk on being burnt (in the brick) becoming quicklime, with all its properties of
swelling in slaking on coming into contact with moisture.
Now my Invention consists in mixing certain substances, as herein-after stated,
with the clay or earth in such manner that when the said clays or earths are made
up into bricks and burnt they shall be of the colour known as white bricks or
similar tint, and at the same time said bricks shall not possess the dangerous
property of swelling or bursting from their composition.
I accomplish this object by mixing with the clay or earth one, or more, or all of
the following substances, namely:- Common limestone which has been previously
burnt and slaked, magnesian limestone which has been previously burnt and
. slaked, magnesium and its compounds, and silica, or gas resulting from the same,
the proper proportion of each ingredient being predetermined by experiments in
the chemical laboratory, and so regulated that the clay or earth and ingredients-
when mixed shall have approximately the same chemical composition as natural
white clays or similar clays, and when burnt shall produce bricks of the desired
white or similar tint at will.
The maguesian or other lime is to be burnt and slaked and thus swollen up to
its maximum bulk previously to being mixed with the clay or earth, and is thus
prevented from exerting any injurious effect on the brick upon coming into contact
with moisture. The light powdered slacked lime or limes and silica are then mixed
with the clay or earth in any suitable machine which will cause the particles of
each ingredient to be thoroughly mixed, and each particle of each ingredient to lie
in close proximity to each other, and in such state of moisture as is best suited to
the particular clay or earth treated.
The addition of these dry ingredients is very valuable in the case of many clays
or earths, in drying the same and rendering them capable of being made into bricks,
and at once burnt without the usual delay and expense incurred in air or other
drying.
In witness whereof, I, the said Robert Pickwell, have hereunto set my hand
11: That 1
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