Improvements in the Manufacture of Enamelled Bricks and Tiles.
Year: 1892

page_text: COMPLETE SPECIFICATION.
Improvements in the Manufacture of Enamelled Bricks and Tiles.
I CHARLES FREDERICK HALL of Audenshaw, near Manchester in the County
of Lancaster, Enameller on Wrought Iron and Experimenting Chemist 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, that is to say :-
My said invention relates to an improved methol of enamelling or glazing bricks
and tiles. As at present carried out, the process of enamelling bricks is effected
by dipping the side or end of the brick when in a dried condition, but before being
burnt, into a liquid or semi-liquid mixture containing the glazing or enamelling
ingredients.
The coating thus deposited upon the brick is allowed to dry and the dipping
operation is repeated as often as may he thought necessary. The bricks are
afterwards burned in a kiln and the process of firing melts the glaze and effects the
enamelling of the dipped surfaces. This ordinary process is both tedious and
unreliable and my invention consists of an improved mode of effecting the same
object in a more expeditious and economical manner.
According to my improved method I take the bricks after they have been fired
in the kiln in the usual manner, and set the side or end which I wish to enamel
upon a plate heated from beneath and keep it there until the side or end in contact
with the plate is of a bright red heat. I then place the brick with its heated side
uppermost upon a dry table or plate to receive the enamel. The enamel is applied
in the form of a fine dry powder, and I might apply it at one operation when
coloured or dark goods are required, but I prefer to apply the powders in two
distinct coats, when a white enamel is required. The powder which I apply first
when producing white enamelled goods consists of a grey enamel composed of the
following ingredients mixed in the indicated proportions

page_text: pounded sieved and subjected to the action of a magnet to take out any particles of
iron or steel that may be present. The resulting fine powder is sifted or dusted
equally over the heated surface of the brick which as I have described has already
been coated with a layer of the grey enamel powder. This second coating of
powder melts over the first skin of grey enamel and forms an even white glaze or
enamel. The brick is now transferred to an annealing oven and slowly cooled.
It will be understood that although I have given lists of ingredients and
approximate proportions from which to make the enamelling powders, I do not
bind myself to the stated proportions or to the ingredients. The enamelling
powders do not in fact form part of my present invention and I have stated their
composition merely to render my Specification as complete and full as possible.
The composition and proportion of the powders will also be governed largely by
the nature of the clay from which the bricks are made. For example, in mixing
the first grey enamel powder I might add thereto certain other ingredients
combined or uncombined such as carbonate or hydrated oxide of potassium or
sodium borate of lead and soda or anhydrous borax in small quantities and
intimately mixed with the powdered grey enamel. This I find necessary in certain
cases to prevent the glaze being taken out of the enamel, by the silica and alumina
of the brick or tile combining chemically with the enamel, thus forming a hard
unglazed and greasy looking surface.
In the case of coloured enamelled bricks I treat the brick in the same manner as
for white goods using an enamel coloured with the necessary oxide or oxides of
metal. When the colour or tint is light or delicate in shade it is better to apply
the enamelling powders in two operations so as to preserve the purity of the shade
in the second coating as in the case of the white enamelled goods, but where the
colour is dark or when a black enamel is required the enamelling powder may be
sifted on in one application. When so applied at one operation I use the enamel
powder first described adding thereto the necessary darkening or colouring oxide
such for example as cobalt oxide for blue, copper oxide for green, and so on such
colouring media being common knowledge to those acquainted with the preparation
of these descriptions of enamel.
In this manner I am enabled to enamel any kind of brick the heat-resisting
nature of which is sufficient to enable it to resist fire for the time required for
powdering on the enamel. By mixing hard enamel and soft enamel together in the
requisite proportions I am enabled to adapt them to almost any kind of clay. The
advantages arising from my process are cheapness and expedition in glazing, no
time being lost in dipping, drying and scraping off the excess of enamel as in the
old method. My improved process is applicable to the softer varieties of clay and
will enamel even the common red building bricks.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
The improved manufacture or method of glazing or enamelling burnt bricks or
tiles, by heating the surface which it is proposed to enamel and applying to the
said heated surface a sufficiency of finely powdered enamel of a suitable composition
so as to coat and glaze the surface and thereafter annealing the brick or tile sub-
stantially as hereinbefore described.
Dated this 17th day of June 1892.
E. K. DUTTON & Co.,
5, John Dalton Street, Manchester, Agents.
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