AN IMPROVEMENT OB IMPROVEMENTS IN THE MANUFACTURE OF MELTING POTS OR CRUCIBLES
Year: 1861

page_text: LETTERS PATENT to Robert Mushet, of Coleford, in the County of
Gloucester, Metallurgist, for the Invention of "AN IMPROVEMENT OB
IMPROVEMENTS IN THE MANUFACTURE OF MELTING POTS OR CRUCIBLES."
PROVISIONAL SPECIFICATION left by the said Robert Mushet at the
Office of the Commissioners of Patents, with his Petition, on the 26th
January 1861.
I, ROBERT MUSHET, of Coleford, in the County of Gloucester, Metallurgist,
do hereby declare the nature of the said Invention for "AN IMPROVEMENT
OR IMPROVEMENTS IN THE MANUFACTURE OF MELTING POTS OR CRUCIBLES," to be as
follows:-
My Invention consists in manufacturing melting pots or crucibles from the
mixture of certain clays herein-after described, the said mixture of clays being
combined with the usual admixture of old pot or burnt clay and coke dust.
Melting pots or crucibles made according to my Invention are especially
intended to be employed for the purpose of melting steel or homogeneous iron
metal, or any mixture of steel-producing materials or of homogeneous iron-
producing materials, into cast steel or into cast homogeneous metal respectively.
The said crucibles are also, however, well suited for use when the melting of
other substances besides steel and homogeneous iron has to be effected at an
intense heat or high temperature.
The clays which I prefer to employ for my process are the kaolin or china

page_text: clay of Cornwall or Devon, and the best black or grey fire-clay of Staffordshire.
The kaolin clay which I find best suited for my process is that raised by the
Leemoor China Clay Company at Leemoor, near Plymouth, and the kind of
black or grey fire-clay which I prefer to employ is that raised at the Freehold
Clay Works near Stourbridge. But I do not confine myself to the use of
these particular varieties of kaolin or china clay and black or grey fire-clay,
for other varieties of these clays, or clays having the same or nearly the same
composition may be employed without departing from the nature of my
Invention. I prepare the kaolin or Leemoor china clay for my purpose by
passing it through a riddle of from 64 to 100 meshes per square inch.
I prepare the black or grey fire-clay for my purpose either by slaking
it into a fine powder by sprinkling water over it, or I grind it under
edge runners, or I press it through rollers and pulverise it, so as to
pass through a riddle of from 64 to 100 meshes per square inch. When
thus prepared and riddled the black or grey fire-clay is ready for my process..
I do not, however, confine myself to the use of riddles of the exact degree of
fineness herein set down, for finer or coarser riddles may be employed for
passing the clays through. But I have found that when riddles of the degree
of fineness I have herein set down are made use of, the clay is well prepared
for my purpose, and the melting pots manufactured from the said clay are
excellent. I further break up and free from the adhering slag and sand a
quantity of melting pots or crucibles which have been used for melting steel in,
and I grind or crush this old pot or cement so as to pass through a riddle of
from 64 to 100 meshes per square inch. I also grind or crush a quantity of
clean hard coke, manufactured by preference from bituminous or anthracite pit
coal, and pass the said ground or crushed coke through a riddle such as I have
herein-before described. The old pot or cement and the coke thus prepared
are ready for my purpose. I do not, however, confine myself to the use of old
pot or cement or of pit coal coke for my process, for other materials, such as
burnt fire-clay and the carbonaceous matter found encrusting the insides of gas
retorts, may be employed in place of old pot and pit coal coke. But I find
that old pot or cement and ground coke are economical and answer very well
for my purpose, but I do not claim the use of either old pot, burnt clay, pit
coal coke, or gas carbon as ingredients to be employed in the manufacture of
melting pots or crucibles.
When I am about to manufacture melting pots from the materials I have
herein-before described I proceed as follows:-To five bushels by measure of
the prepared black or grey fire-clay I add five bushels of the prepared kaolin
or Leemoor china clay, one bushel of prepared old pot or cement, and one

page_text: bushel and a half of the prepared coke. I mix these pulverised substances
carefully and thoroughly, and I then add as much water as will convert the
mixture of the said substances into a plastic mass which is the pot clay I employ
out of which to manufacture my melting pots or crucibles. But I do not
confine myself to the relative proportions of kaolin clay to fire-clay herein set
down, as these proportions may be varied without departing from the nature of
my Invention, but I find in practice that the pots manufactured from these
proportions of the respective ingredients are excellent in quality; nor do I
confine myself to the proportions of prepared old pot and coke dust herein set
down, for they may be varied, but I have found that these proportions
answer well.
I next proceed to temper or knead the mass of pot clay obtained as I have
described so as to render the said pot clay very tough and plastic and of uniform
texture throughout the mass. I then divide the tempered pot clay into Limps
of the weight required to form the melting pots intended to be made, and I
roll and ball up these lumps of clay in the ordinary manner ready for placing in
the pot flask or mould, wherein the manufacture of the melting pots is com-
pleted. The pots are then moulded and finished in the usual manner, and are
then stored on shelves to dry, and when dried are annealed for use in an
ordinary annealing grate and in the manner usually practised by steel manu-
facturers and others.
The pot clay may be kneaded or tempered in any convenient manner, either
by workmen treading it with their feet in the usual manner, the clay being
placed upon a clean smooth floor or stage, preferably of iron plates, or the pot
clay may be tempered in an ordinary clay pug mill.
Melting pots manufactured from the materials I have described possess the
advantage of being exceedingly strong when intensely heated, and they are so
close and dense in their texture that the metal melted in the said pots rarely
escapes, which, when inferior pots are employed frequently occurs. My melting
pots also do not soften or yield with the most intense heat which a cast steel
melting furnace can give them, so that even when the pots are of very large-
size they will carry the great weight of metal with which they are charged
without risk of the weight of the said metal when melted rending the pot and.
escaping.
Other Kaolin clays similar to the Leemoor clay and other fire-clays of a
nature similar to the black or grey fire-clay of Staffordshire may be employed,
but I have found that the clays herein named make most excellent melting
puts, capable of withstanding the utmost heat of a steel melting furnace.
Having thus described the nature of my Invention and the methods by which

page_text: I carry it into effect, I declare that what I claim is the manufacture of melting
pots or crucibles from a mixture of kaolin or china clay and black or grey
fire-clay of Staffordshire, or similar black or grey fire-clays of a refractory
nature. To the said mixture of the said clays I add the usual adjuncts of
pulverised old pot or cement and pulverised pit coal coke, but I do not claim
the use of the said pulverised old pot or pit coal coke as of my Invention, and
burnt clay or gas carbon may be employed in place of old pot and ground coke
respectively, as herein-before described; plumbago also may be added to my pot
clay mixture, but such addition forms no part of my Invention, neither is it
essential to the success of the said Invention.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Robert Mushet in the Great Seal Patent Office on the
23rd July 1861.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ROBERT
MUSEET, of Coleford, in the County of Gloucester, Metallurgist, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-sixth day of January, in the year of our Lord
One thousand eight hundred and sixty-one, in the twenty-fourth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said Robert Mushet, Her special licence that I, the said Robert Mushet, my
executors, administrators, and assigns, or such others as I, the said Robert
Mushet, 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
terin 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 "AN IMPROVEMENT OR IMPROVEMENTS
IN THE MANUFACTURE OF MELTING POTS OR CRUCIBLES," upon the condition
(amongst others) that I, the said Robert Mushet, my executors or adminis-
trators, by an instrument in writing under my, or their, or one of their
bands 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 Robert Mushet, 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:-

page_text: My Invention consists in manufacturing melting pots or crucibles from the
mixture of certain clays herein-after described, the said mixture of clays being
combined with the usual admixture of old pot or burnt clay and coke dust.
Melting pots or crucibles made according to my Invention are especially
intended to be employed for the purpose of melting steel or homogeneous iron,
metal, or any mixture of steel-producing materials, or of homogeneous iron-
producing materials into cast steel or into cast homogeneous iron, commonly
called homometal, respectively. The said crucibles are also, however, well
suited for use when the melting of other substances besides steel and homo-
geneous iron has to be effected at an intense heat or high temperature.
The clays which I prefer to employ for my process are the kaolin or china
clay of Cornwall or Devon, and the best black or grey fire-clay of Staffordshire.
The kaolin clay which I find best suited for my process is that raised by the
Leemoor China Clay Company at Leemoor near Plymouth, and the kind of
black or grey fire-clay which I prefer to employ is that raised at the Freehold
Clay Works or at the Amblecote Clay Works near Stourbridge. But I do
not confine myself to the use of these particular varieties of kaolin or china
clay and black or grey fire-clay, for other varieties of these clays, or clays
having the same or nearly the same composition may be employed without
departing from the nature of my Invention. I prepare the kaolin or Leemoor
china clay for my purpose by passing it through a riddle of from 64 to 100
meshes per square inch. I prepare the black or grey fire-clay for my pur-
pose either by slaking the lumps or pieces of the said clay into a fine powder
by sprinkling water over the said lumps of clay, or I grind the said lumps of
clay under edge runners, or I pass the said lumps of clay through rollers, and
pulverise the clay so as to pass through a riddle of from 64 to 100 meshes
per square inch. When thus prepared the black or grey fire-clay is ready
for my process. I do not, however, confine myself to the use of riddles of the
exact degree of fineness herein set down, for finer or coarser riddles may be
employed for passing the clays through; but I have found that when riddles
of the degree of fineness I have herein set down are made use of, the clay is
well prepared for my purpose, and the melting pots manufactured from the
said clay are of excellent quality. I further break up and free from the
adhering slag and sand a quantity of melting pots or crucibles which have
been used for melting steel in, or have been otherwise calcined at an intense
heat, and I grind or crush this old pot, called also "cement," so as to pass
through a riddle of from 64 to 100 meshes per square inch. I also grind or
crush a quantity of clean hard coke, manufactured by preference from bitu-
minous or anthracite pit coal, and pass the said ground or crushed coke

page_text: through a riddle such as I have herein-before described. The old pot or
cement and the coke thus prepared are ready for my purpose. I do not,
however, confine myself to the use of old pot or cement or of pit coal coke
for my process, for other materials, such as burnt fire-clay and the carbonaceous
matter found encrusting the insides of gas retorts, or plumbago, may be
employed in addition to or in place of old pot and pit coal coke respectively.
But I find that old pot or cement and ground coke are economical, and
auswer very well for my purpose; but I do not claim the use of either old
pot, burnt clay, pit coal coke, or gas retort carbon as ingredients to be
employed in the manufacture of melting pots or crucibles, for the said ingre-
dients are employed in the manufacture of other melting pots or crucibles.
When I am about to manufacture melting pots from the materials I have
herein-before described I proceed as follows:-To five bushels of the prepared
black or grey fire-clay I add five bushels of the prepared kaolin or Leemoor
china clay, one bushel of prepared old pot or cement, and one bushel and a half
of the prepared coke. I mix these pulverised substances carefully and tho
roughly, and I then add as much water as will couvert the mixture of the said
substances into a plastic mass, which is the pot clay I employ out of which to
manufacture my melting pots or crucibles. But I do not confine myself to
the relative proportions of kaolin clay to fire-clay herein set down, as these
proportions may be varied without departing from the nature of my Invention,
but I find in practice that the pots manufactured from these proportions of
the respective ingredients are excellent in quality; nor do I confine myself
to the proportions of prepared old pot and coke dust herein set down, for
they may be varied, but I have found that these proportions answer well.
I next proceed to temper or knead the mass of pot clay obtained as I have
described, so as to render the said pot clay very tough and plastic, and of
uniform texture throughout the mass; I then divide the tempered pot clay
into lumps of the weight required to form the melting pots intended to be
made, and I roll and ball up these lumps of clay in the ordinary manner
ready for placing in the pot, flask, or mould wherein the manufacture of the
melting pots is completed. The pot, flasks, or moulds I employ are similar
to those ordinarily employed in the manufacture of melting pots or crucibles.
The pots are then moulded and finished in the usual manner, and are after-
wards stored on shelves to dry, and when dried are annealed for use in an
ordinary annealing grate, and in the manner usually practised by steel manu-
facturers and others.
The pot clay may be kneaded or tempered in any convenient manner, either
by workmen treading it with their feet in the usual manner, the clay being

page_text: placed upon a clean smooth floor or stage, made preferably of iron plates, or
the pot clay may be tempered in an ordinary clay pug mill.
Melting pots manufactured from the materials I have described possess the
advantage of being exceedingly strong when intensely heated, and they are
so close and dense in their texture that the metal melted in the said pots
rarely escapes, which when inferior pots are employed frequently occurs. My
melting pots also do not soften or yield when exposed to the most intense heat
which can be produced in a cast steel melting furnace, so that even when the
pots are of very large size they will carry the great weight of metal with
which they are charged without risk of the weight of the said metal when
melted rending the pot and the metal escaping.
Other kaolin clays similar to the Leemoor clay and other fire-clays of a
nature similar to the black or grey fire-clay of Staffordshire may be employed,
but I have found that the clays herein named make most excellent melting
pots capable of withstanding the utmost heat of a steel melting furnace.
Having thus described the nature of my Invention, and the methods by
which I carry it into effect, I declare that what I claim is the manufacture of
melting pots or crucibles from a mixture of kaolin or china clay and black or
grey fire-clay of Staffordshire, or similar black or grey fire-clays of a refractory
nature. To which said mixture of the said clays I add the usual adjuncts of
pulverised old pot or cement and pulverised pit coal coke; but I do not claim
the use of the said pulverised old pot or pit coal coke as of my Invention, and
burnt clay or gas carbon may be employed in place of old pot and ground coke
respectively, as herein-before described. Plumbago also may be added to my
pot clay mixture, but such addition form no part of my Invention, neither is it
essential to the success of the said Invention.
In witness whereof, I, the said Robert Mushet, have hereunto set my
hand and seal, this Twentieth day of July, in the year of our Lord
One thousand eight hundred and sixty-one.
Witnesses,
BROOKLYN MUSHET,
Coleford, Gloucestershire.
EDWD. M. MUSHET,
Coleford, Gloucestershire.
ROB. MUSHET. (LS.)