A KIND OF PORCELLAIN NEWLY INVENTED BY ME, COMPOS'D OF MOOR STONE OR GROWAN AND GROWAN CLAY
Year: 1768

page_text: TO ALL PEOPLE TO WHOM THESE PRESENTS SHALL COME, I.
WILLIAM COOKWORTHY, of Plymouth, in the County of Devon, Chemist, send
greeting.
WHEREAS His most Gracious Majesty King George the Third, by Letters
Patent, bearing date at Westminster, the Seventeenth day of March now last
past, did give and grant unto me. the said William Cookworthy, my executors,
adñiors. and assigns, Iis especial licence, full power, sole priviledge and
authority, that I, the said William Cookworthy, my executors, adiñors, and
assigns, and every of us, by myself and themselves, or by mine and their
deputy or deputys, servants or agents, or such others as I, the said William
Cookworthy, my executors, adñiors, or assigns, should at any time agree with,
and no others, from time to time and at all times thereafter during the term of
years therein expressed, should and lawfully might make, use, exercise, and vend
A KIND OF PORCELLAIN NEWLY INVENTED BY ME, COMPOS'D OF MOOR STONE OR
GROWAN AND GROWAN CLAY," within that part of His Majesty's Kingdom of
Great Britain called England, His Dominion of Wales, and Town of Berwick-
upon-Tweed, in such manner as to me, the said William Cookworthy, my
executors, admors, and assigns. or any of us, should in our discretion seem
meet, and that I, the said William Cookworthy, my executors, adñiors, and
assigns, should and lawfully might have and enjoy the whole profit, benefit,
commodity, and advantage from time to time coming, growing, accruing, and
arising by reason of the said Invention, for and during the term of years
therein mentioned, to have, hold, exercise, and enjoy the said licence, powers,

page_text: priviledges, and advantages therein-before granted unto me, the said William
Cookworthy, my exccutors, adñiors, and assigns, for and during and unto the
full end and term of fourteen years from the date of the said Letters Patent
next and immediately ensuing, and fully to be compleat and ended, according
to the Statute in such case made and provided; in which said Letters Patent
there is contained a provisoe as or to the effect following (viz'), that if I, the
said William Cookworthy, should not particularly describe and ascertain the
nature of my said Invention, and in what manner the same was to be per-
formed, by an instrument in writing under my hand and seal, and cause the
same to be inrolled in His Majesty's High Court of Chancery within four
calender months next and immediately after the date of the said Letters Patent,
that then the said Letters Patent, and all libertys and advantages whatsoever
thereby granted, should utterly ceasc, determine, and become void, as in and
by the said Letters Patent (relation being thereunto had) more fully and at
large it doth and may appear.
NOW KNOW YE, that I, the said William Cookworthy, in pursuance of
the said recited provisoe, do, by this my Deed in writing, declare and make
known the nature of my said Invention, and the quality of the materials, and
manner in which the same is performed, which is as followeth (that is to
say):
The materials of which the body of the said porcellain is composed are a
stone and earth or clay. The stone is known in the countys of Devon and
Cornwall by the names of moor stone and growan, which stones are generally
composed of grains of stone or gravel of a white or whiteish colour, with a
mixture of talky shining particles. This gravell and these talky particles are
cemented together by a petrified clay into very solid rocks, and immense quan-
titys of them are found in both the above-mentioned countys. All these
stones, exposed to a violent fire, melt without the addition of fluxes into a
semi-transparent glass, differing in clearness and beauty according to the purity of
the stone. The earth or clay, for the most part, lyes in the valleys where the
stone forms the hills. This earth is very frequently very white, tho' some-
times of a yellowish or cream colour. It generally arises with a large mixture
of talky micee, or spangles, and a semi-transparent whiteish gravell. Some
sorts have little or none of the mice or spangles, but the best clay for making
porcellain always abounds in micæ or spangles. The stone is prepared by
levigation in a potter's mill in water in the usual manner to a very fine powder.
The clay is prepared by diluting it with water untill the mixture is rendered
sufficiently thin for the gravell and mice to subside, the white water containing
the clay is then poured or left to run off from the subsided micæ and gravell

page_text: into proper vessells or reservoirs, and after it has settled a day or two, the
clear water above it is to be then poured or drawn off, and the clay or earth
reduced to a proper consistence by the common methods of exposing it to
the sun and air, or laying it on chalk. This earth or clay gives the ware its
whiteness and infusibility as the stone doth its transparence and mellowness;
they are therefore to be mix'd in different proportions as the ware is intended
to be more or less transparent. and the mixture is be performed in the method
used by potters and well known (viz, by diluting the materials in water,
passing the mixture through a fine sieve, and reducing it to a paste of a proper
consistence for working in the way directed for the preparation of the clay).
This paste is to be form'd into vessells, and these vessells when biscuited are
to be dipp'd in the glaze, which is prepar'd of the levigated stone with the
addition of lime and fern ashes, or an earth called magnesia alba, in such
quantitys as may make it properly fusible and transparent when it has received
a duc degree of fire in the second baking.
In witness whereof, I, the said William Cookworthy, have hereunto
sett my hand and seal, this Eleventh day of July, in the eighth year
of the reign of our Sovereign Lord George the Third, by the grace of
God of Great Britain, France, and Ireland King, Defender of the
Faith, and so forth, and in the year of our Lord One thousand seven
hundred and sixty-eight.
WILLIAM (L.S.) COOKWORTHY.
Signed, sealed, and delivered by the
AND BE IT REMEMBRED, that on afores" Eleventh day of July,
in the year above mentioned, the aforesaid William Cookworthy came before
our said Lord the King in His Chancery, and acknowledged the Specification
aforesaid, and all and every thing therein contained and specified, in form above
written. And also the Specification aforesaid was stampt according to the
tenor of the Statute made in the sixth year of the reign of the late King and
Queen William and Mary of England, and so forth.
Inrolled the Fourteenth day of July, in the year above written.