Improvements in the Manufacture of Porous Earthenware.
Year: 1889

page_text: COMPLETE SPECIFICATION.
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 (which has
been communicated to me from abroad by Charles Carroll Gilman, of Eldora, Iowa,
United States of America, Gentleman), and in what manner the same is to
be performed, to be particularly described and ascertained in and by the following
statement:—
My invention relates to porous earthenware products, and it has for its object to
supply artificially to such structures a fibre indestructible by the fire used in converting
clays into bricken products.
As heretofore made, Terra Cotta lumber, and kindred products, resemble wood
timber only in that they may be readily operated upon with edge-tools, for the vegetable
matters which are incorporated into the plastic composition are driven out by the firing
process to which the compressed plastic mass is subjected, subsequent to pressing into
form, leaving behind a burned residuum possessing merely the quality of affording
a tensile strength measured by the tenacity with which the particles comprising said
residuum adhere to one another. Certain of the formulæ by which the wares in
question are made, provide that cut straw, or its equivalent, may be added to the
green mixture for the purpose of affording a fibre serving as a temporary means of
tying the green wares together, in order that they may dry without cracking and be
more safely handled when dried; but as the straw is combustible it perishes in the
subsequent process of firing, leaving the wares, when burned, destitute of the fibrous
strength which characterized them when green.
I propose by my invention to supply a fibre to the clay, or clayey compositions,
which will remain as an element of the porous brick product after it has been subjected
to the firing process, whereby a high degree of tensile strength is permanently
imparted to the structure.
To accomplish the result in question I interpose sparsely, but intimately with the
plastic compositions the prepared asbestos of commerce known as asbestine wool.
In carrying out my invention the asbestine wool in quantities determined by
strength required of burned product may be sprinkled from time to time upon the
exposed surface of the clayey composition containing the vegetable matters as they
are turned by the workman, with shovels or otherwise, upon the floor preparatory to
going to press. I use in this manner from twenty (20) pounds upwards of the
asbestine wool to about one ton of the burned composition.
In making any of the various porous earthenwares-the manufacture of which
being now familiar to all Clay-workers, needs no special explanation in this descrip-
tion the vegetable matter employed therein must not be diminished in quantity
because of the addition of the asbestos for the latter supplies nothing to the porosity
of the burned product, inasmuch, as is well known, it will not be destroyed by the
firing process.
Asbestos when milled and prepared for market, usually presents the appearance of
wool, and is designated commercially as of long and short fibre. For the purposes of
the present invention I make use, by preference, of the long fibre, and this comes in
the largest quantities from the mines of North Carolina, U.S.
After the mineral fibre is properly, and in sufficient quantities incorporated into
the plastic composition by turning on the floor as explained, the mixture is then run
through the press of the type described as Expressive." The composition is forced
through the dies of the press onto the cutting table in hard compressed slabs or forms
of. the required sizes, etc. These compressed forms are subsequently dried and then
subjected to the firing process in the kilns, where they are burned in the same manner
as common building brick, the vegetable matters being burned out in the firing process.

page_text: The wares, thus finished, if broken and subjected to close examination will reveal the
asbestine fibres-little diminished in strength by reason of having been under
the influence of the fire-tightly drawn for the most part like short strings, parallel
with the grain of the pressed composition, this arrangement of the fibres and the grain
of the ware, being caused by the friction which the plastic composition encounters in
its enforced passage through the dies of the press.
I have demonstrated by experiments that wares such as herein mentioned are
possessed of a tensile strength, due to the incorporated mineral fibres, which can be
obtained in no other way. This increased tensile strength is very desirable, if not
indispensable, in many cases where the porous brick product in question is. now
commonly used; and the presence of the mineral fibres in such of the wares as are
used in the erection of fire-proof structures is not a source of danger, as the added
fibres which confer the extraordinary tensile strength are incombustible and hence in
no degree detract from the effectiveness of the earthenware product as fire-proof
building material.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is
· A burned porous earthenware product having incorporated therein fibres of asbestine
wool, substantially as described.