IMPROVE- MENTS IN THE MANUFACTURE OF ARTIFICIAL STONE
Year: 1877

page_text: LETTERS PATENT to Archibald Campbell Ponton, of the City and County of
Bristol, and of Bournemouth, in the County of Hants, Architect, and Fellow
of the Royal Institute of British Architects, for the Invention of " IMPROVE-
MENTS IN THE MANUFACTURE OF ARTIFICIAL STONE"
PROVISIONAL SPECIFICATION left by the said Archibald Campbell Ponton
at the Office of the Commissioners of Patents on the 14th May 1877.
ARCHIBALD CAMPBELL PONTON, of the City and County of Bristol, and of Bourne-
mouth, in the County of Hants, Architect, and Fellow of the Royal Instituto of
British Architects. "IMPROVEMENTS IN THE MANUFACTURE OF ARTIFICIAL STONE."
According to this Invention I apply sulphur and other materials to the production
or manufacture of an artificial stone or material of a hard and firm nature from
sand, loam, clay, gravel, or other suitable earthy or mineral substances, with or
without the addition of Portland cement or other suitable cement or cementitious
matter.
In order to properly carry out this manufacture I first ascertain the quantity of
sulphur required by correctly ascertaining the amount of the voids in any of the
above materials or combinations of materials, which should be so selected or
combined as to present a minimum amount of voids, which latter are to be filled
with the sulphur. Thus, as a mere example, when combining, say, some sands of
different sorts, I may select them so that the average size or diameter of particles
of one sand are fifty or more times larger than those in the other. I find that
various natural sorts of gravel, sand, loam, and clay found in and about the neigh-
bourhood of Bournemouth and in many other parts of the country, are suitable for
this manufacture.
The proportions of the combinations vary with the degrees of fineness of particles,
but should be so that the smaller particles of a finer material or materials as much
as possible fill up the voids between the larger particles of a coarser material. I
may thus, for instance, mix one kind of fine sand with, say, an equal weight of clay,

page_text: thereby reducing the voids in the sand from, say, 33 per cent. of the bulk to about
one-half that; or if I add only half its weight of clay I reduce the voids to about
11 per cent. or by adding to six of one kind of gravel, say, two of a certain sand
and one of clay, I may reduce the voids to about 5 per cent. of the whole bulk; or
I may further reduce the voids in sands or compositions of clays and sand by the
admixture of Portland or other suitable cement or cementitious matter which forms
water of crystallization in a per-centage of the voids.
I blend the materials or combinations thereof with flower of sulphur or other
sulphur powder; thus for clay I use powdered sulphur to the extent of about double
the weight of the water necessary to make the clay plastic, and I work this into the
clay; I then work into the material such sand or sand and gravel or cement as I
may require, together with any coloring matter. If required, I treat the loam and
sand and other compositions aforesaid in the same way with the exception that
when there is no clay, such as in sand compositions where clay is omitted, the voids
are still estimated by the quantity of water which such sand compositions will
absorb when in a dry compounded condition. The material in a moist plastic state
is then formed or moulded into any required shape, which may be done in a mould
or by rollers, applying such pressure as may be needful. I heat the articles so
made in an oven or chainber, either when out of the moulds or while still in them,
to a temperature of about 250° F. or so as to melt the sulphur in the composition;
the articles when cold are then found to have become hard and to resist the influence
of water; or the articles with or without the admixture of the powdered sulphur
(but by preference without) are in the heated state immersed in a bath of molten
sulphur combined or not with coloring matter. The moisture may first be evapo-
rated and the article then subjected to heavy pressure before immersion in the
sulphur bath. If the articles are immersed while in the moulds the latter are made
of a porous material, such as plaster of Paris or cement, so that the molten sulphur
can penetrate the mould and then enter into the pores of the material in the mould.
When cool the articles will be found to be very dense and hard, more especially in
those cases where great pressure has been used in making the articles.
The above-described modes for introducing sulphur into clay I also apply to
obtain a hard coating upon stucco, concretes, bricks, or tiles. I mix with Portland
or other cement, ground fine, such clay, sand, and colouring matter as I require, and
I estimate the quantity of voids and mix such a quantity of flowers of sulphur or
powdered sulphur as will fill the voids of the coating; I then make these mixed
powdered substances into a paste with water, and trowel them over or otherwise
apply them to the stucco, concretes, bricks, or tiles of the thickness I require for
the coat.
When the coat is hard and dry I melt the sulphur in combination with the
coating by means of hot irons, bags of hot sand or hot air, or other suitable heating
I also coat
appliances; or if the articles coated can be placed in an oven I do so.
concretes, bricks, and tiles with Portland or other cement mixed with such clay or
sand and colouring matter as I require, and I heat the concrete bricks or tiles, and
when hot I immerse the coated portions only in molten sulphur. Instead of sulphur
I may use resinous or bituminous materials or compounds.
The articles may, if required, go through a process of tooling, smoothing, or
polishing for embellishment, before the melted sulphur is in the pores or afterwards.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Archibald Campbell Ponton in the Great Seal Patent Office on the
14th November 1877.
ARCHIBALD CAMPBELL PONTON, of the City and County of Bristol, and of Bourne-
mouth, in the County of Hants, Architect, and Fellow of the Royal Institute of
British Architects. "IMPROVEMENTS IN THE MANUFACTURE OF ARTIFICIAL STONE."
According to this Invention I apply sulphur to the production or manufacture of
an artificial stone or material of a hard and firm nature from sand, loam, clay, gravel,
or other suitable earthy or mineral substances with or without the addition of
Portland cement or other suitable cement or cementitious matter.
In order to properly carry out this manufacture I first ascertain the quantity of
sulphur required by correctly ascertaining the amount of the voids in any of the
above materials or combinations of materials, which should be so selected or
combined as to present a minimum amount of voids, which latter are to be filled
with the sulphur; and in order to enable the sulphur to fill the voids properly any
air or water present in the interstices of the material or combination of materials
should be removed. As a mere example, when combining, say, some sands of
different sorts, I may select them so that the average size or diameters of particles
of one sand are fifty or more times larger than those in the other. I find the
various natural sorts of gravel, sand, loain, and clay found in and about the neigh-
bourhood of Bournemouth and in many other parts of the country are suitable for
this manufacture.
The proportions of the combinations vary with the degrees of fineness of particles,
but should be so that the smaller particles of a finer material or materials as much
as possible fill up the voids between the larger particles of a coarser material. I
may thus, for instance, mix one kind of fine sand with, say, an equal weight of clay,
thereby reducing the voids in the sand from, say, 33 per cent. of the bulk to about
one-half that; or if I add only half its weight of clay I reduce the voids to about
11 per cent.; or by adding to six of one kind of gravel, say, two of a certain sand
and one of clay, I may reduce the voids to about 5 per cent. of the whole bulk; or
I may further reduce the voids in sand or composition of clay and sand by the
admixture of Portland or otlier suitable cement or cementitious matter.
I apply sulphur for filling up the interstices of any article composed of fine-
grained powder, such as of slag or glass, or of clays, loams, flints, carbonate or
sulphate of lime, burnt or unburnt, or of felspar, Cornish stone, or other suitable
earthy or mineral or metallic substances.
Any of these aforesaid materials may, if desired, be mixed with suitable pigments
or coloring matter so as to produce any required tint. I use these aforesaid hard-
grained powdered materials, tinted or not, for the manufacture of fine-grained
artificial stone, so fine that if the interior surfaces of the moulds be polished the
castings will have a polished surface.
For the manufacture of a coarser grained stone I mix one part by weight of the
aforesaid powdered materials, tinted or not, with one or more parts of clean, sharp
sand of a coarser grain than that of the aforesaid powder.
For the manufacture of a concrete I mix shingle or gravel with the before-
mentioned finer materials.
For the manufacture of a coarse concrete I mix boulders or flints with the first-
mentioned mixture of materials.
I estimate the proportions of the aforesaid powder and other materials by calcu-
lating the amount of the interstices, which the finer sorts fill when mechanically
mixed with the coarser sorts. I fill moulds with any one or other of these before-
mentioned materials when moist or dry, using as much compression, either by
ramming, tamping, or rolling or otherwise, as can conveniently be applied, or by
means of suitable presses. The moulds are preferably porous, and may be con-
structed of plaster of Paris, wood, papier maché, cement, or other porous substance,

page_text: or of metal or glass, with suitable aperture or apertures for the admission of the
nolten sulphur.
If the materials in the moulds are wet or moist I carefully dry the same before
indurating with sulphur.
If I wish to indurate rapidly I pack the articles on the filled moulds inside an air-
tight receiver, and heat the receiver and contents up to about 240° Fahrenheit, thus
removing the water contained in the material, and then, by means of an air pump
or other appliance, I remove the air or a portion of the air; by this removal of the
air I also prevent discoloration of the outer surfaces of the articles in the mould
during induration; I then submerge the receiver in molten sulphur; or, if desired,
the air may be removed while the receiver is submerged in the sulphur. The air
being removed the sulphur is admitted by opening a valve or equivalent appliance,
or the removal of the air may be effected simultaneously or partly so while the
sulphur enters.
When the materials have become saturated with sulphur I withdraw the aforesaid
receiver and allow the superfluous sulphur to drain into the tank containing the
molten sulphur. I withdraw the castings from the receiver, and remove any moulds
or cores which may have been employed, and, where necessary, rub, tool, polish, and
embellish the castings.
Where speed of induration is not required I merely soak the articles or the filled
moulds in molten sulphur, and withdraw from the tank containing the sulphur
when sufficient saturation of sulphur is obtained.
In those cases where steam under pressure is available I prefer to steam jacket
the tank for the supply of heat; a float and index may be used to ascertain when
the articles are saturated with sulphur, the float assuming a state of rest when the
saturation is completed; a thermometer may be used fitted with alarum appliance for
indicating maximum and minimum temperature.
In those structural cases where it is necessary to resist the action of fire, I uso
either Portland or other cement, or loam or clay, to bind the particles together.
Where the particles are thus held together it is unnecessary to indurate in the
moulds, but it is desirable to heat or burn the loam or clay mixture before induration.
I also indurate with sulphur, hydraulic cements, either when used alone or when
mixed with sand, and non-absorbent materials.
Articles having a certain amount of cohesion before induration will, after indura-
tion with sulphur, be found greatly increased in strength, and those which had no
original cohesion and are indurated in the moulds will be found stronger than solid
sulphur or most natural stones; the moulds also by the exclusion of the air, as
already stated, serve the purpose of preventing discoloration of the surfaces of the
Inaterial or article moulded therein; during induration the moulds should therefore,
as aforesaid, be in an air-tight receiver, or the material or materials to be indurated
may be protected by a covering, say, of pasteboard or paper.
The articles may, if required, go through a process of tooling, smoothing, or
polishing for embellishment, either before the melted sulphur is in the pores or
afterwards.
And having thus described the nature of this Invention, I wish it to be understood
that I do not claim the application in general of sulphur for indurating materials,
as I am aware that sulphur in solution has heretofore been proposed to be used for
indurating natural and artificial stones; also that molten sulphur has been proposed
to be used for indurating soft and porous stones, hard artificial stones from chalk,
plaster, and porous stones in general; but I claim,—
First. The production of artificial stone from one or more materials, having little
or no cohesion amongst the particles by immersing those materials whilst in a mould
in molten sulphur, substantially as herein set forth.
Second. The production of artificial stone by first compounding materials, the
particles of one material or materials serving to materially fill the interstices between
the particles of the other material or materials, the said compound being then.

page_text: indurated, moulded, or, while in a mould, by the application of molten sulphur
substantially as set forth.
Third. The production of artificial stone from fine-grained powder, such as of Blag,
glass, clays, loams, flints, carbonate or sulphate of lime, felspar, Cornish stone, or
other suitable earthy or mineral or metallic substances, moulded, or while in moulds,
by induration with molten sulphur, the air being excluded or extracted during
induration, substantially as set forth.
Fourth. The induration of natural and artificial porous stones by means of molten
sulphur, the air being excluded or extracted during such induration, substantially
as set forth.
In witness whereof, I, the said Archibald Campbell Ponton, have hereunto
set my hand and seal, this Ninth day of November, in the year of our Lord
One thousand eight hundred and seventy-seven.
ARCHIBALD CAMPBELL PONTON. (L.S.)
15 Witness to signature of
A. C. Ponton,
W. CH. JACKSON, Bournemouth.
EDWIN WOOD,
"