IMPROVEMENTS IN CRUCIBLES, MELTING POTS, RETORTS, FURNACES, AND OTHER ARTICLES SUBJECTED TO AN ELEVATED TEMPERATURE
Year: 1869

page_text: LETTERS PATENT to John Henry Johnson, of 47, Lincoln's Inn
Fields, in the County of Middlesex, Gentleman, for the Invention
of "IMPROVEMENTS IN CRUCIBLES, MELTING POTS, RETORTS, FURNACES, AND
OTHER ARTICLES SUBJECTED TO AN ELEVATED TEMPERATURE."--A communi-
- cation from abroad by Auguste Ponsard, of Paris, in the Empire
of France.
Sealed the 31st May 1870, and dated the 7th December 1869..
PROVISIONAL SPECIFICATION left by the said John Henry Johuson at
the Office of the Commissioners of Patents, with his Petition, on
the 7th December 1869.
I, JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County
of Middlesex, Gentleman, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN CRUCIBLES, MELTING POTS, RETORTS, FUB-
NACES, AND OTHER ARTICLES SUBJECTED TO AN ELEVATED TEMPERATURE," a com-
munication to me from abroad by Auguste Ponsard, of Paris, in the
Empire of France, to be as follows;-
This Invention relates to a mode of treating refractory substances

page_text: having a carbonaceous base with a view to increasing their durability by
protecting them from the destructive action of oxidising gases, and con-
sists in the manufacture of crucibles, melting pots for glass or metals,
retorts, furnaces, linings for furnaces and converting vessels from refrac-
tory materials having a carbonaceous base mixed with fire-clay, the
article or substance thus produced being subsequently coated with a more
or less fusible protective coating according to the degree of heat which the
article or substance is required to withstand. This protective coating is
caused to adhere to the carbon in the refractory material by saturating or
coating the surface of the article with a strong solution of chloride of
calcium in water before applying the fusible protective coating. The
plastic refractory substances employed consist of aluminous or silicous
earth, alumina, magnesia, or other like substances of a more or less
plastic nature, with which carbon is to be mixed or incorporated, the
carbon employed being in the form of coke, graphite, anthracite, wood,
charcoal, and the like reduced to a more or less fine state of division
according to the intended application and the dimensions of the articles
to be treated. The article having been formed from the plastic
refractory materials above referred to it is well coated with a strong
solution of chloride of calcium, and then dried in a stove or furnace,
after which it receives a second coating or paint composed of materials
capable of fusing at a temperature approximating to that to which the
article is required to be subjected, such materials consisting, for example,
of silica and clay moistened with a solution of chloride of calcium in
varying proportions according to the more or less refractory properties
required.
In the case of linings for furnaces, converting vessels, and the like,
the lining may be first applied, and then coated in situ with the chloride
of calcium and protective coating above described.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said John Henry Johnson in the Great Seal Patent
Office on the 7th June 1870.

page_text: WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Seventh day of December, in the
year of our Lord One thousand eight hundred and sixty-nine, in the
thirty-third year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said John Henry Johnson, Her special
license that I, the said John Henry Johnson, my executors, adminis-
trators, and assigns, or such others as I, the said John Henry Johnson,
my executors, administrators, or 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 CRUCIBLES, MELTING POT, RETORT, FURNACES,
ARTICLES
SUBJECTED
AND OTHER
to
communication
TO AN ELEVATED TEMPERATURE," a
me from abroad by Auguste Ponsard, of Paris, in the Empire of
France, upon the condition (amongst others) that I, the said John
Henry Johnson, my executors or administrators, by an instrument
in writing under my hand and seal, 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 John Henry Johnson, 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:-
The said Invention relates to a mode of treating refractory substances
having a carbonaceous base with a view to increasing their durability
by protecting them from the destructive action of oxidising gases,
carbon, and particularly the variety known under the name of plumbago,
has been long employed, either alone or mixed with a certain quantity
of clay, for the construction of articles which are required to sustain
the most elevated temperatures and withstand the action of fluxes, such,
for example, as plumbago crucibles and crucibles covered with damp
charcoal. These articles last for a considerable period when they are
not placed in contact with an oxidizing atmosphere, but on the contrary
they are destroyed in a few hours when the gases in which they are

page_text: -paced contain an excess of oxygen, and there remains then a species of
skeleton formed by the plastic material employed to impart consistence
to the carbonaceous paste.
The object of the present Invention is to obtain by means of the
different varieties of carbon, such, for example, as coke, graphite, an-
thracite, charcoal, graphite from gas retorts, a substance possessing all
the qualities of plumbago combined with greater durability. These
materials are cheap, but as they are ill adapted for withstanding
combustion they cannot be advantageously used alone.
D
'According to this Invention it is proposed in order to effect the
desired result to cover the products made with these substances with
a protective coating, which enables every description of separating
material to be manufactured and applied to the construction of crucibles,
furnace hearths, vaults, and even to the entire construction of reheating
furnaces and glass furnaces, linings for Bessemer converters, crucibles,
and linings of blast furnaces, steel crucible furnaces, kilns for the baking
of ceramic products, saggars, pots for glass works and their banks, basins
for glass melting furnaces without crucibles, and to other like purposes.
The pieces or articles (such, for example, as crucibles, hearths, vaults,
and bricks) are formed as in the ordinary manner with a paste composed
of aluminous and silicious earth, alumina, magnesia, and other more or
less plastic materials, and carbon, such, for example, as coke, graphite,
anthracite, and charcoal reduced into grains, the size of which varies
according to the use and dimensions of the articles which it is required
to make. The pieces having been made and dried are covered with a
highly concentrated solution of chloride of calcium, which penetrates
the dry materials to a certain depth, and is perfectly refractory. This
first layer is then dried in a stove and coated with a coating composed
of materials susceptible of being melted at a temperature approaching
to that to which the pieces will be subsequently subjected. These
materials are silica and clay diluted with a solution of chloride of
calcium, the proportion of which varies according to the degree of
temperature to which the articles made are to be subjected and to the
refractory quality which it is required to impart to them. These
materials on melting form a glaze, the object of which is to cover the
pieces with a continuous layer, which protects the carbon from contact
with the oxidising gases. As a guide to the composition of this coating I

page_text: to that which the article or substance will be required to sustain
during its ordinary use. The furnace being thus finished it is fired
by raising the temperature gradually to from 200° to 300° Centigrade,
so as to completely dry the whole; the fire is then urged on briskly,
the gases of combustion being maintained as reducing as possible until
the melting heat of the glaze is attained. The glazing having now
been formed covers the sides of the furnace with a continuous layer,
which preserves the carbon from contact with the oxidising gases,
and as these materials are not subjected to any further sensible contrac-
tion or expansion it follows that the duration of the furnace is, so to
speak, indefinite.
In order to ensure the result of the operation precaution may be
taken to cover the layer of the coating which is to form the glazing,
and which is not to be melted, except at a very high temperature, with
another very fusible coating, such as a glazing having a base of boraric
acid, soda, or oxide of lead, and which on melting at the commence-
ment of the heating of the furnace forms a glazing, which temporarily
preserves the carbon from contact with the air until the refractory
glazing, properly so called, is raised to the melting heat.
The paste of graphite or coke not being susceptible of contraction,
and being a good conductor of heat and capable of sustaining changes
of temperature without breaking, may be employed in the course of
working for repairs of the hearths or other surfaces.
Having now described and particularly ascertained the nature of the
said Invention, and the manner in which the same is or may be used or
carried into effect, I would remark in conclusion that what I consider
to be novel and original, and therefore claim as the Invention secured
to me by the herein-before in part recited Letters Patent is, the appli-
cation and use of refractory materials having a carbonaceous base in
combination with a mixture of refractory earth, and in the manufacture
of crucibles, retorts, pots of glass works, hearth and vault pieces, and
for other like purposes, also to and in the entire construction of furnaces
working at a high temperature by the addition thereto of a glaze more
or less fusible according to the temperature to which the pieces or
articles are to be submitted, such glaze being caused to adhere to the
carbon which forms the paste by the previous application of a solution
of chloride of calcium dissolved in water, which by impregnating the

page_text: arbonaceous paste for a certain thickness with a highly refractory and
xed product, protects it after the glazing subsequently applied has been
estroyed by wear, substantially as herein-before described.
In witness whereof, I, the said John Henry Johnson, have to this
my Specification set my hand and seal, the Seventh day of June
One thousand eight hundred and seventy.
J. HENRY JOHNSON. (L.S.)