AN IMPROVED PORCELAIN
Year: 1839

page_text: TURNER AND MINTON'S SPECIFICATION.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, WILTON
GEORGE TURNER, of Park Village, Regent's Park, Doctor in Philosophy,
and HERBERT MINTON, of Longfield Cottage, in the Parish of Stoke-upon-
Trent, in the County of Stafford, Manufacturer, send greeting.
WHEREAS we did by our petition represent unto Her most Excellent
Majesty Queen Victoria that we had invented "AN IMPROVED PORCELAIN,"
that we were the first and true inventors thereof, and that the said Invention
had never been practised or used by any other person or persons whomsoever
to our knowledge and belief, and did thereby pray that Her said Majesty
would be graciously pleased to grant unto us, our exors, adñors, and assigns,
Her Royal Letters Patent for the sole use, benefit, and advantage of our said
Invention, within England, Wales, and the Town of Berwick-upon-Tweed,
for the term of fourteen years, pursuant to the Statute in that case made and
provided; and Her said most Excellent Majesty Queen Victoria, being willing
to give encouragement to all arts and inventions which might be for the
public good, was graciously pleased to condescend to our request, and by Her
Letters Patent under the Great Seal of Great Britain, bearing date at West-
minster, the Twenty-second day of June, in the third year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto us, the said
Wilton George Turner and Herbert Minton, our exors, admors, and assigns,
Her especial licence, full power, sole privilege and authority, that we,
the said Wilton George Turner and Herbert Minton, our exors, adñors,

page_text: and assigns, and every of us, by ourselves or by our deputy or deputies,
servants or agents, or such others as we, the said Wilton George Turner and
Herbert Minton, our exors, admiors, or assigns, shall at any time agree
with, and no others, from time to time and at all times thereafter during
the term of years therein expressed, shall and lawfully may make, use,
exercise, and vend our said Invention within that part of Her Majesty's
United Kingdom of Great Britain and Ireland called England, Her said
Majesty's Dominion of Wales, and Town of Berwick-upon-Tweed, in such
manner as to us, the said Wilton George Turner and Herbert Minton, our
exors, adiñors, and assigns, or any of us, shall in our discretions seem meet;
and that we, the said Wilton George Turner and Herbert Minton, our exors,
adñiors, and assigns, shall and lawfully may have and enjoy the whole profit,
benefit, commodity, and advantages from time to time coming, growing, accruing,
and arising by reason of the said Invention, for and during and unto the full
end and term of fourteen years from the date of those Presents next and
immediately ensuing, and fully to be complete and, ended, according to the
Statute in that case made and provided; in which said Letters Patent there is
contained a proviso obliging us, the said Wilton George Turner and Herbert
Minton, by an instrument in writing under our hands and seals, or under the
hand and seal of one of us, particularly to describe and ascertain the nature
of our said Invention, and in what manner the same is to be performed, and
to cause the same instrument to be enrolled in Her said Majesty's High Court
of Chancery within six calendar months next immediately after the date
of the said Letters Patent, as in and by the same, reference being thereunto
had, will more fully and at large appear.
NOW KNOW YE, that in compliance with the said proviso, we, the said
Wilton George Turner and Herbert Minton, do hereby declare that the nature
of our said Invention consists in producing the biscuit prepared for glazing of
a much softer and more porous nature, by subjecting it to a much less degree
of heat than heretofore used for that purpose, and when the glaze has been
put upon the biscuit so produced, in subjecting the said porous biscuit to a
much greater degree of heat than is usual for the mere purpose of glazing, and
effecting the glazing at the same time.
And in further compliance with the said proviso, we, the said Wilton George
Turner and Herbert Minton, do hereby describe the manner in which our
said Invention is to be performed by the following statement thereof, that is
to say :-
A quantity of kaolin or Cornish clay is so long agitated with a portion of
water that the whole is brought to the consistence of cream; it is then passed

page_text: through a fine sieve, by which all foreign matter as well as the coarser portions
are separated. A gallon or any other convenient measure of this cream-like
liquid is evaporated to dryness, and the residue weighed, from which the
quantity of solid matter in any number of gallons of the cream of the liquid
may be calculated. A portion of Dorsetshire or similar clay is treated in a
similar manner. To so many gallons of the first cream-like liquid as shall
contain one hundred pounds of solid kaolin, and of the second as shall contain
five pounds of solid Dorsetshire clay, are added twenty pounds of a pure feld-
spar, ground to an impalpable powder; the whole, after long continued stirring
to effect as intimate an admixture as possible, is passed through a fine silk
lawn sieve. This sifting is to be repeated three times, a perfect admixture
being thus effected. The mixture must next be dried until it be reduced to
a plastic clay; this may be done by the common process of drying it upon the
slip kiln. The clay being sufficiently dried is manufactured into various articles
exactly as the common earthenware of this country. The process of firing is,
however, somewhat different, and is most economically conducted in an oven
of three stories or three chambers one above the other, as shewn in the
Drawing annexed. In this Drawing, Figure 1 is a sectional elevation of such
a three-storied oven; Figure 2, a ground plan of the basement or lower
chamber A; Figure 3, a plan of the first story or chamber B; and Figure 4, a
which it will be seen that the
plan of the second story or upper chamber C,
heat passes up from the chamber A to the chamber B through pipes or chimnies
raised above the floor, whereby the heat is rendered less than it would
otherwise be in that chamber. By reference to the plans it will also be seen
that the apertures for the passage of the heat from chamber to chamber are
not exactly over each other, but purposely mismatched, so that the heat is
necessarily drawn across the upper chambers in its passage upwards, and thus
wanders more thoroughly among the saggers. The first fire to which the
greenware is exposed should not be so strong as to cause any sensible
contraction of the greenware, but be merely sufficient to harden it into a kind'
of bisque, so far as to enable the workman to handle it freely, and to prevent it
from again softening when introduced into water, although it remains. very
porous and highly absorbent, and for this purpose the greenware should be
baked or fired first in the chamber B. It is thus brought into the best state
for receiving the glaze, which must be composed on this principle, that it does
not flow into a perfect glass until the bisque is fired up and forms a perfect
porcelain, and must be more or less fusible, in proportion to the hardness of the
body; a number of different compositions will answer this purpose. The
following is an example of one glaze which may be advantageously used upon

page_text: the body above specified. This glaze is composed of twenty-eight parts of
common flint calcined and ground in water, as used in the potteries for various
purposes; or instead thereof, the same quantity of Lynn sand or of finely ground
silica in any shape it can be procured pure, eight parts of the soft bisque
herein before described fired up, and then broken and finely ground in water,
eight parts of gypsum of the purest sort finely ground in water, eighteen
parts of kaolin or Cornish clay previously prepared by mixing with water, and
sieving the several above-mentioned ingredients to be ground separately, and
separately passed through a silk lawn sieve of the finest sort;. the above
ingredients are then to be completely dried separately on a kiln, or in any other
eonvenient method, and weighed, then put together into a large quantity of
water, and thoroughly mixed by stirring; and to effect the mixture more
completely, the whole when mixed together must be passed twice through
a silk lawn sieve of the finest sort; the workman, while passing the glaze
through the sieve must keep the liquid in the vessel, from which it is taken to
pass through the seive, agitated so as to preserve a complete mixture of the
materials, and prevent a subsidence of the heavier particles. The materials
should then be allowed to subside, and the superfluous water drawn off, leaving
the glaze of about the consistency of cream, in which the bisque ware is to be
dipped. The glaze being thus put upon the biscuit ware by dipping, and the
biscuit ware being placed in saggers, made in manner herein-after described,
may be fired up in the chamber A, which should not be of greater height than
about six feet inside measurement, because if the bungs much exceed six fect
in height, the lower saggers are liable to be crushed by the superincumbent
weight when placed in the chamber A; the fire should be continued at a great
heat until trials drawn from the oven in the usual way show that the glaze
has flowed smoothly and uniformly, the strong heat firing up the body as it is
called, and effecting the glazing at the same time. Now, it is evident that the
saggers used for the foregoing purpose must be made to stand the strong heat
applied to the ware as before described, which ordinary saggers would not, and
they should therefore be made in the following manner:-They should not be
composed of the common Staffordshire marl, as is usual, but made of the
following materials in the following proportions, that is to say, six hundred-
weight of common Dorsetshire clay mixed with four hundredweight and a
quarter of grog, which is formed from setters crushed between rollers commonly
called a grog mill. The grog should not be too fine, the best sort is that
which is obtained from setters or from saggers made after this process, and
then passed through a sieve in which the interstices will admit a common pea
to pass through; these ingredients are intimately mixed to the consistency of

page_text: the clay generally used in the formation of common saggers, and used in the
same manner.
Now, whereas we claim as our Invention the improved porcelain aforesaid,
that is to say, porcelain made as aforesaid, the body of which has been fired up
as aforesaid at the same time that the glazing has been perfected, or porcelain
made as aforesaid the glazing of which has been perfected at the great heat
aforesaid, after the body has been previously fired up by a similar heat; and
such our Invention being to the best of our knowledge entirely new and never
before used in that part of Her Majesty's United Kingdom of Great Britain
and Ireland called England, Her Dominion of Wales, or Town of Berwick-
upon-Tweed, we do hereby declare this to be the Specification of the sail
Invention; wherefore we do hereby claim and maintain exclusive right and
privilege to our said Invention.
In witness whereof, wc, the said Wilton George Turner and Herbert
Minton, have hereunto set our hands and seals, this Twelfth day
of December, One thousand eight hundred and thirty-nine.
WILTON GEORGE TURNER. (L..S.)
HERBERT MINTON.
Signed, scaled, and delivered by the above-
named Wilton George Turner (being first
duly stamped), in the presence of
ROD Y. GREEN,
(L.S.)
AND BE IT REMEMBERED, that on the Twelfth day of December,
in the year of our Lord 1839, the aforesaid Herbert Minton came before our
5 said Lady the Queen in Her Chancery, and acknowledged the Specification
aforesaid, and all and every thing therein contained and specified, in form
above written.

page_text: AND ALSO BE IT REMEMBERED, that on the Fourteenth day of Decemi-
ber, in the year of our Lord 1839, the aforesaid Wilton George Turner came
before our said Lady the Queen in Her Chancery, and acknowledged the Speci-
fication aforesaid, and all and every thing therein contained and specified, in
form above written. And also the Specification aforesaid was stamped
according to the tenor of the Statute made for that purpose.
Inrolled the Sixteenth day of December, in the year of our Lord One
thousand eight hundred and thirty-nine.