Improvements in the Manufacture of Porous Earthenware.
Year: 1886

page_text: Date of Application, 30th Nov., 1886.
Specification Accepted, 15th Apr., 1887.
[Communicated from abroad by CHARLES CARROLL GILMAN, of Eldora, Iowa, United
States of America, Gentleman.]
Improvements in the Manufacture of Porous Earthenware.
I, HERBERT JOHN ALLISON of 52 Chancery Lane, London, in the County of
Middlesex, Patent Agent, do hereby declare the nature of this invention and in
what manner the same is to be performed to be particularly described and ascertained
in and by the following statement :-
The object of my invention is to create a new material for construction purposes
which alone or in combination with other substances affords a worthy competitor as
against brick, stone and lumber.
My invention relates to the mixing of carily and vegetable matters made plastic
by addition of water in certain proportion and manner, and a subsequent treatment
which yields in the end a porous earthenware product. The raw ingredients entering
into the compound are clay, or clayey loam, short cut straw, or its equivalent, and
granular vegetable matter, as sawdust for example. Clay or clayey loam is the base
of the compound in all the stages of manufacture save the last, when all the other
ingredients are eliminated, and it remains as a residue or final product. The short
cut straw, or its equivalent, affords a fibre to the mixture in the second and third
stages of manufacture, and is used to bind or tie it together. The sawdust or
granular vegetable matter which is liberally incorporated in the mixture, serves as
fuel with which to bake the clay, while both the straw, and sawdust are destroyed by
combustion in the fourth stage of manufacture and renders the baked clay product
cellular or porous. Five separate and distinct processes, or steps are required to
convert the raw material herein before named into the finished material and are as
follows, Mixing, Pressing, Drying, Firing, and Tooling.
The manipulations of the raw ingredients, and their subsequent treatment may be
described as follows:-
I take clay of any variety, which if gravelly must first be freed from the grit, and by
grinding or rolling in any manner practiced by clay workers, I reduce it to a
pulverized condition. For ordinary purposes surface clays are preferable to fictile, or

page_text: kaolin clays, so termed, as the former are common to every country, are easier to
work and bake with less heat. To the clay I add the vegetable matters before
described by measure in proportion, varied, according to the sort of material I wish to
produce, and to its future specific application. If long pieces like joists or beams
are required, say up to ten feet in length (which may be further strengthened to
resist transverse strains by the addition of metal cores, which are made subsequent to
firing by running molten iron into the longitudinal holes created by the die when the
material is in a plastic state) I use fibrous vegetable matter only in the mixture, that
is, straw, or its equivalent, chopped into lengths of two inches or thereabouts. Nails
may be driven into this material but it is not susceptible of tooling by ordinary
methods. If a product of great porosity be demanded, which may be advantageously
wrought with wood working tools subsequent to firing, then granular vegetable
matters only may be used in the mixture, if those of fibrous nature are not easily.
obtained to mix them with. Mixtures which will afford products intermediate in
strength and porosity between these two extremes may be had by varying the added
quantities of vegetable matter, of either or both sorts described. For instance for
sills, girders, fence posts, railroad ties and like construction (which may be further
strengthened with iron cores, and which are penetrable by nails) two parts of straw,
and one of clay by measure are the usual proportions. For blocks to build outsidé
walls of buildings which to resist moisture must before erection be coated with a thin
slip of cement or stucco or for underground construction, as for example pavements,
pavement foundations, electrical insulations, tunnel linings &c. impregnated with
boiling asphaltum, the formula recommended is two parts by measure of clay, two of
sawdust, and one of straw. For chimneys, chimney flues, sheathing for roofs, to
which slates may be nailed, or cement, metal and asphalt coverings applied, and for
columns, and all interior work, as partition walls, ceilings, furring, or lining of
exterior walls, and sub-floors, and other class of work upon which it is desirable to
apply mortar by trowelling, a mixture of two parts of clay, three of sawdust by
measure, accompanied by a sprinkling of straw best serves the purpose; and for
boiler jackets, steam pipe coverings, filtering slabs, and safe and vault linings (in
which latter the material may be or may not be injected with alum water or the like)
as high as two parts of sawdust to one of clay by measure, to which a sprinkling of
straw may be added or not, affords the proper mixture. The products of the two
last described mixtures may be wrought with common saws, and edged tools, and
will hold nails, or screws, measurably well. The earthy and vegetable matters in
measured proportions, adapted to the subsequent use of the product as described are
intimately mingled together with the addition of sufficient water to make the
compound plastic by any of the various tempering or pugging processes known to
brick making; which by thorough incorporation thereof will afford homogeneity
of mass, a qualification absolutely demanded when tooling subsequent to firing is
required. The method which I recommend however is to measure and evenly
distribute over and upon each other the prepared earthy and vegetable matter in
alternate layers proportioned in quantity to the supposed demand for future use of the
product, and dampened, as the layers accumulate over each other, by sprinkled
water. A pile thus composed of dampened alternate layers may be built up to a
height of several feet, and upon completion must be covered with old bagging,
blankets, or carpeting, thoroughly wetted to prevent evaporation, and to insure an
even distribution of moisture through the mass, and may be suffered to stand
untouched forty-eight hours or more. Two principles of pressing are utilized in the
formation of products of clay. To wit, "compression," and "expression." Machines
of the former are used to fill stationary moulds with plastic clay, as is done with brick,
roofing, and floor tiles, and the like. Of the latter to press the clay mixture while in
motion by pushing it with great power through hollow dies. I use presses embodying
the latter principle for moulding my mixtures, though occasions sometimes arise for
forms of product which cannot thus he made, in which case I press the plastic
material by hand with moulds of requisite shape. If the pile prepared as described be
within convenient distance of the press, its contents may bo shovelled directly into the

page_text: press. If not, they may be thrown upon an endless belt, and conveyed thither, first
being dislodged from the end or side of the pile by workmen with sharpened shovels,
who cut off thin sections down from the top through the intermediate layers to the
bottom, taking care to intermix the ingredients, composing the individual layers
by gentle agitation, shovelling over and over before the mixture is thrown into the
press. The latter, which may be of the "auger" variety is a large iron cylinder
horizontally mounted, and gently tapering from its receiving end on which there is
located a hopper to receive its load, toward the delivery end, the mouth of which is
blocked by a die attached thereto with bolts, and which is easily removable, and
interchangeable with others of different patterns. A screw or auger is adjusted to
its interior, the blades of which are attached to a horizontal revolving shaft, and
pitch forward toward the delivery end of the press at an angle of thirty degrees.
Pushed forward by the revolving screw the mixture is not only "pugged," or
worked together into a plastic condition in its passage, but is compressed with great
power, a compression greatly enhanced when the resistance to its progress, offered by
the die, is met. The friction thus encountered causes the fibrous particles to arrange
themselves longitudinally and parallel with the axis of delivery.
Around and
through the die the contents pass and emerge beyond upon a receiving table, in a
solidly pressed compact column, corresponding to the form of the die. Moving
forward with constant steady motion, the column is divided into gauged lengths by an
attendant workman, and carried to the drying yards or rooms. If the mixture be of
straw and clay only, these lengths may be as great as ten feet or more. If of sawdust
and clay only, from twelve to sixteen inches. If of clay, sawdust and straw, of a
length intermediate between the two, depending upon the proportion of fibrous matter
intermixed.
DRYING.
These pressed blocks or slabs may be dried, when the climate and season will
allow проп racks under out-of-door sheds. In winter seasons within the house by
heat artificially applied. Unlike green products of pure clay, the sudden application
of heat does not cause the blocks to warp or crack even when submitted to a heat as
high as 185° Fahrenheit as it comes from the press. Drying by artificial means
requires from twenty-four to forty-eight hours, and by natural atmospheric influences
from sixty to one hundred under favorable conditions.
FIRING.
As each block or piece contains vegetable matter enough after ignition to bake the
clay contained therein (that is, if sawdust is used, but not straw alone) the dried
product may be burned in any sort of a kiln, either up or down draught. The
brickmaker's up draught kiln for firing common building brick is however preferred.
Apply sufficient kindling, of coke, coal or wood to the fire holes to fairly ignite the
contents when a gradual combustion of the vegetable matter will soon follow until
the whole interior of the kiln, as viewed through the peep-holes, appears in a state of
incandescence. Now close tightly all draughts and regulate the fire by the guarded
admission of air through small flues or apertures. A cherry red heat 950°
Fahrenheit and no greater must be maintained until combustion has entirely ceased,
nor must the kiln be opened thereafter until thoroughly cool. If this process be
properly performed, every portion of the kiln's contents will be found to have baked
alike and to be of the same color.
TOOLING.
All mixtures containing sixty per cent of sawdust or greater may be tooled with
ordinary saws and wood working machinery subsequent to firing, a process however
not always necessary in fitting the product for market.
T

page_text: its non-conducting qualities of heat, cold, sound, and electricity. The property of
molecular attraction causes mortar and cements to adhere with tenacity, and that of
capillary attraction (for it will conduct fluids upward like a cotton wick) to take up
dampness and moisture and evaporate the same at a higher plane. In its natural
state it serves admirably for filtering and refrigerating purposes, and combined with
asphalt it becomes water proof, and uncombined is practically indestructible by fire,
acids, and age.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is
First. That improvement in the art of making porous earthenware, which consists
in mixing clay with vegetable matter, expressing the mixture through a press, drying
the same, and burning it in a kiln substantially as described.
Second. That improvement in the art of making porous earthenware, which consists
in mixing clay with vegetable matter, expressing the mixture through a press, drying
the same, burning it in a kiln, and finally shaped with edged tools to the desired form
substantially as described.
Third. That improvement in the art of making porous earthenware, which consists
in mixing clay with fibrous vegetable matter cut in short lengths, expressing the
mixture through a press, and subsequently to drying, burning the same in a kiln
substantially as described.
Fourth. That improvement in the art of making porous carthenware which consists
in mixing clay with sawdust and fibrous vegetable matter, cut in short lengths, in
expressing the mixture through a press, and subsequently to drying burning the same
in a kiln substantially as described.
Fifth. That improvement in the art of making porous earthenware which consists
in mixing clay with fibrous vegetable matter with or without the addition of other
vegetable matter, and in expressing the mixture through a press, whereby the pieces
of straw are caused to arrange themselves parallel with each other, and with the ax's
of the press substantially as described.
Sixth. That step in the process of making porous earthenware which consists in
mixing with clay or with a clay and sawdust mixture, a sufficient quantity of straw,
or equivalent material, cut in short pieces to prevent the cracking and shrinking apart
in drying of the mixture substantially as described.
Seventh. A porous earthenware product in large blocks, made by mixing clay,
sawdust and straw, and subsequently expressing and burning the mixture
hereinbefore described.
as
Eighth. A porous earthenware product characterized by longitudinal pores, cells or
holes formed by the burning out of imprisoned vegetable matter substantially as
described.
Ninth. A porous earthenware product made by mixing clay, sawdust and straw,
expressing and burning the mixture, and finally cutting with edged tools substantially
as described.
Tenth. A porous earthenware product made by mixing clay and vegetable matter
and by subsequently expressing the mixture through a press, and finally burning the
same in a kiln substantially as described.
Datal the 30th day of November 1886
ALLISON BROS.,
Agents for the Applicant.