IMPROVEMENTS IN THE MANUFACTURE OF MOSAIC PLAQUES OR SLABS SUITABLE FOR EXTERNAL AND INTERNAL DECORATIONS
Year: 1870

page_text: LETTERS PATENT to Colin Minton Campbell, of the Firm of Minton
and Company, China and Earthenware Manufacturers, of Stoke-
upon-Trent, and Walbrook, in the City of London, for the Invention
of "IMPROVEMENTS IN THE MANUFACTURE OF MOSAIC PLAQUES OR SLABS
SUITABLE FOR EXTERNAL AND INTERNAL DECORATIONS."
Sealed the 9th August 1870, and dated the 17th June 1870.
PROVISIONAL SPECIFICATION left by the said Colin Minton Campbell
at the Office of the Commissioners of Patents, with his Petition, on
the 17th June 1870.
I, COLIN MINTON CAMPBELL, of the Firm of Minton and Company,
China and Earthenware Manufacturers, of Stoke-upon-Trent, and
Walbrook, in the City of London, do hereby declare the nature of the
said Invention for "IMPROVEMENTS IN THE MANUFACTURE OF MOSAIC PLAQUES
OR SLABS SUITABLE FOR EXTERNAL AND INTERNAL DECORATIONS," to be as
follows:-
The object of this Invention is to obtain the effect of mosaic decorating
by a simpler and more effective process than any of those at present in

page_text: use, and of which the product is quite as permanent as other mosaic
decorations.
In carrying out my Invention I make tesseræ of biscuit of hexagonal
or other convenient form, and by means of heat and a flux I form the
same into plaques of the sizes required by the nature of the subject to be
depicted. In this way I obtain plaques or slabs of a true form, which
could not be attained were it attempted to make them each in a single
piece, as they would warp and twist in the firing, and the joints would
spoil the effect of the composition. On the plaques so made I paint
the various parts of the required pattern, and the plaques or slabs are
refired as often as may be necessary. The various plaques comprising
the whole subject are then united into one whole by means of Portland
or other cement.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Colin Minton Campbell in the Great Seal Patent
Office on the 17th December 1870.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, COLIN
MINTON CAMPBELL, of the Firm of Minton and Company, China and
Earthenware Manufacturers, of Stoke-upon-Trent, and Walbrook, in the
City of London, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Seventeenth day of June, in the year
of our Lord One thousand eight hundred and seventy, in the thirty-
third year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said Colin Minton Campbell, Her special license
that I, the said Colin Minton Campbell, my executors, administrators,
and assigns, or such others as I, the said Colin Minton Campbell, 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 "IMPROVEMENTS IN
THE MANUFACTURE OF MOSAIC PLAQUES OR SLABS SUITABLE FOR EXTERNAL AND
INTERNAL DECORATIONS," upon the condition (amongst others) that I, the

page_text: said Colin Minton Campbell, 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 Colin Minton Campbell, do hereby
declare the nature of the said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and
by the following statement thereof, that is to say:―
The object of this Invention is to obtain the effect of mosaic decoration
by a simpler and more effective process than any of those at present in
use, and of which the product is quite as permanent as other mosaic
decorations.
In carrying out my Invention I make tessera of biscuit of hexagonal
or other convenient form, and by means of heat and a flux I form the
same into plaques of the sizes required by the nature of the subject to
be depicted. In this way I obtain plaques or slabs of true form which
could not be attained were it attempted to make them each in a single
piece as they would warp and twist in the firing, and the joints would
then spoil the effect of the composition. On the plaques so. made I
paint the various parts of the required picture, and the plaques or slabs
are refired as often as may be necessary. The various plaques com-
posing the whole subject are then united into one whole by means of
Portland or other cement.
In order that my said Invention may be most fully understood and
readily carried into effect I will proceed to describe more in detail.
the manner in which I prefer to conduct the manufacture.
I first prepare a number of stoneware, earthenware, china, or porcelain
or glass tessere. The tesseræ are moulded from finely. powdered clay
by means of heavy pressure and are then thoroughly fired or vitrified,.
they should be regular hexagons, about half of an inch thick and three--
fourths of an inch diameter across the opposite angles..
These tesseræ I arrange with their best faces downwards on a true
slate or other table until a surface is covered sufficient for the picture or
design which is to be produced. A tracing of the principal divisions"

page_text: of the picture is laid on the tesseræ thus arranged, and the division lines
are marked which are to divide the subject into a number of plaques
of convenient dimensions. The division lines are arranged so as to
interfere as little as may be with the design. A convenient size for
the plaques is about six inches diameter, but this may be considerably
varied to bring the division lines to suitable positions. The plaques
being thus marked out a hard vitreous flux or cement is placed on the
backs of the tesseræ, care being taken that the cement shall not cover
the division lines.
The flux or cement which I employ consists of seven and a half parts
by weight of fine sand washed and dried, four parts of felspar calcined
and ground fine, five parts of glass pounded fine, four parts of pure
oxide of tin, and two parts of red lead. These ingredients are well
mixed with gum water to the consistence of thin mortar. The gum
water I make by dissolving eight ounces of gum arabic in a gallon of
water. The gum in the cement causes it to dry quite hard and to
adhere strongly to the tesseræ.
When the cement is hard each fragment or plaque is transferred from
the table on to a clay bat with a perfectly level surface, and thus
supported it is placed in an earthenware biscuit oven and there strongly
fired. The cement is thus fluxed or partially melted, and it runs to some
extent between the tesseræ, but the back surface remains rough. This
roughness is advantageous as it enables the Roman or other cement
afterwards used in setting the plaques to adhere firmly.
When the plaques come out of the biscuit oven they are turned face
upwards and an enamel-like flux is poured on the surface and made to
run into the intertices between the tesseræ where the coarser vitreous
cement has not penetrated.
The enamel flux I employ is composed of six parts of felspar, three
parts of borax, three and a half parts of pure oxide of tin, and one part
of sand. The whole is mixed and melted at a strong heat in a biscuit
oven. It is then pounded and ground in a mill in water until it is so
fine as to appear like thick milk. In this very diffused state it is
poured on to the surface of the plaque. It runs into the interstices and
fills them, and the surplus is then wiped off. The plaques are now
placed in an enamelling kiln and strongly fired to thoroughly melt the
enamel flux. When cool the plaques are ready for painting they may

page_text: either be painted separately or may be put together as the artist
desires.
In the painting the ordinary methods of china painting may be
employed, the plaques being refired from time time. When all the
plaques are painted they are set in their places with Roman or other
cement. When the plaques are put together the denticulated form
of the sides of the hexagons brings them to their proper places. If the
work is properly executed the joints will only be visible as a fine
hexagon tracing over the face of the picture.
Having thus described the nature of my said Invention, and the manner
of performing the same, I would have it understood that what I claim as
my Invention of improvements in the manufacture of mosaic plaques
or slabs suitable for external and internal decoration is, the combination
of vitreous or fired tesseræ by means of heat and a flux, so as to form
plaques or slabs on which pictures or designs are then produced and
fixed by firing, substantially as described.
In witness whereof, I, the said Colin Minton Campbell, have here-
unto set my hand and seal, this Fifteenth day of December, in
the year of our Lord One thousand eight hundred and seventy.
COLIN MINTON CAMPBELL. (L.S.)