Year: 1887

page_text: Date of Application, 1st Nov. 1887
Specification Accepted, 2nd Dec., 1887
I, PAUL VON KRYSTOFFOVITCH, of St. Petersburg, in the Empire of Russia,
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:-
This invention relates to a process for the manufacture of artificial granite to be
called "Pyrogranite."
The process is carried out by mixing in the proportion of 2 to 1 dry pulverized or
granular fire-clay with red-clay previously baked in brick moulds and reduced
to a pulverized or granular condition; this dry mixture is then converted into
a thick paste by adding water and stirring; after standing for some time it is
placed in brick-moulds and dried until the substance will resist the pressure of the
fingers; it is finally made under high pressure into the required shape, completely
dried, and baked.
The coefficient of refraction of the fire-elay must not be below 4.00 (Bischoff); its
loss of weight through baking must not exceed 10 per cent; the amount of oxide of
iron contained therein must not exceed 1.50 per cent, and the amount of silicic acid
must not be below 50 per cent.
'
The coefficient of refraction of the red clay must be from 0.50 to 1 (Bischoff) its
loss of weight through baking must not exceed 5 to 6 per cent; it must contain from
13 to 17 per cent of oxide of iron and from 45 to 55 per cent of silicic acid.
The preparation of the material is effected in the following manner :-
The fire-clay is dried, ground, and sifted through a fine sieve so as to reduce it to
a pulverized or granular condition.
The red clay is mixed with sufficient water to produce a paste of uniform thickness
from which blocks are formed advantageously measuring not more than about
150 x 75 x 50 millemetres. These blocks are well dried and baked in brick-moulds
until the temperature reaches a point at which the clay will commence to fuse. This
temperature is indicated by the interior of the blocks presenting a reddish black
appearance when broken. The edges of the blocks must show traces of their having
commenced to fuse and it is very important that the blocks should not be baked for
too long a time otherwise bubbles and fine holes are produced therein. If the blocks
are well baked they will be of homogeneous, dense and hard nature.
The baked bricks are broken and ground and sifted through a fine sieve and in this
manner pulverized.
The two pulverized materials in a dry state are mixed together in the following
proportions, videlicet, 1-5 to 2 parts of the fire-clay powder to 0.75 to 1 part of the red
clay powder.
Water is then added until a thick paste is formed which is stirred for a short time
and then heaped up into the form of a pyramid and covered with wet canvas and left

page_text: for from 24 to 48 hours. After this time the compound is again kneeded, after which
it is advantageous to leave it covered with wet canvas for twenty four hours more.
Blocks are then formed, from this compound, care being taken that all the blocks
shall be of the same size and weight; these blocks are dried until they well resist the
pressure of the fingers; they are then pressed in a press into the required shape such
for example as that of paving-stones or paving-slabs. After the blocks in the form
of stones or slabs have been pressed they are dried until they become hard after
which they are placed on their edges in the brick-kiln and each row is covered with
well dried granules of unbaked fire-clay in order to prevent the stones from adhering
together through the high temperature. In the brick-kiln a temperature of 1000
to 1200 degrees centigrade has to be maintained.
The fire-clay by reason of its said coefficient of refraction will not alter its form nor
become soft under the said temperature.
The red-clay however cannot withstand this temperature; it fuses and becomes
quite liquid, but as the granules of this clay have been previously carefully combined
with those of the fire-clay, it follows that the red-clay, converted into a liquid
substance, will flow around, envelope and unite with the granules of fire-clay whereby
the whole substance will become intimately combined without changing the form
given to the blocks in the press.
By this perfectly homogeneous and dense union the blocks are converted into
stones, which as regards their hardness will compare favourably with the best
granite and when broken present a beautiful and nearly black colour.
The cooling of the stones after baking must be effected as slowly as possible so as
to prevent them from splitting.
These stones when polished have the appearance of marble. They can be made of
various colours, as the colour depends on the baking temperature and on the quantity
of red-elay added to the fire-clay.
They can be made of the following colours, videlicet;-black, reddish-black,
brown of different shades and brilliant colours of different shades.
If the red-clay be employed in the form of coarse grains of the size of a poppy-seed
or a pin-head and cleaned from dust by sifting, the stone will have the appearance of
white marble or granite with black spots. In these cases the red-clay does not
completely fuse the coarse grains fuse on their surface whilst the interior part
remains intact and forms the black spots. If fine powder be employed the stone will
have the appearance of Labrador stone. The described substance is suitable for making
excellent strong pipes and thin durable tiles.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I claim is
"
The herein described process for the manufacture of artificial granite, called
pyrogranite the said process consisting in mixing in the proportion of 2 to 1
pulverized or granular fire-clay with red-clay, baked in brick-moulds and then reduced
to a pulverized or granular state, the said mixture in a dry condition being then
converted into a thick paste by the addition of water and stirring the same, dried to a
certain extent pressed into the required size and shape dried completely and finally
laked under a temperature of 1000 to 1200 degrees centigrade by which temperature
a complete or partial fusion of the red-clay is effected whereby the stone without
being altered in shape becomes of extraordinary hardness and solidity.
T
1
1047
G. F. REDFERN & Co.,
4, South Street, Finsbury, London,
Agents for the Applicant.