Improvements in the Manufacture of Rough, Glazed, and Coloured Facing-stones.
Year: 1890

page_text: Date of Application, 25th Jan., 1890-Accepted 9th Aug., 1890
Improvements in the Manufacture of Rough, Glazed, and Coloured
Facing-stones.
A communication from WILHELM DEISSNER, of Leipsig-Eutritzsch, in the Empire
of Germany.
I, ALFRED JULIUS BOULT of 323 High Holborn in the County of Middlesex, M.I.M.E.,
do hereby declare the nature of this invention and in what manner the same is to
be perforined, to be particularly described and ascertained in and by the following
statement :-
:―
So-called facing stones are frequently employed in architecture for the decoration
of internal and external walls. Where natural stones cannot from any cause be made
use of, these facing stones have hitherto as a rule been manufactured of clay. Clay
facing-stones, no matter how they may have been manufactured or employed, have
however shown themselves subject to a variety of inconveniences and drawbacks.
Rough facing-stones of clay, owing to their porosity, have displayed the disagreeable
characteristic of becoming moss-covered and destroyed by damp, in addition to which
the color with which they have been covered is liable to destruction and alteration
through the action of the weather. Glazed clay facing stones are affected by frost
and heat and split cracking the glaze which has been melted on to them, and so
disfigure the walls which have been ornamented with them, as the glaze flakes off,
and the clay stones thus laid bare are exposed to the destructive action of the
weather.
The present invention has for its object the manufacture of cement-facing-stones
devoid of the above mentioned objections, and possessing all the requirements which
can be demanded of a handsome, durable facing-stone which shall not be easily acted
on by the weather. The facing stones manufactured by this process may be employed
for all kinds of architectural and industrial purposes with the greatest advantage and
can be guaranteed to look well and keep in good condition whether rough or glazed.
An additional advantage is that these new facing stones can be made and finished
everywhere for instance at the very place of erection in the case of large buildings,
since the necessary materials and apparatus are extremely portable.
The method of manufacture employed for rough stones resembling natural facing-
stones in color and appearance is as follows:-
Good Portland cement is intimately mixed with fine sand in the proportion of 1:3
and the mixture moistened with water, but not sufficiently to render it plastic, it is
then pressed into moulds of the form of which it is desired to make the stones, by the
application of strong pressure. Immediately after the pressing of the stones those of
their sides which are to receive a different color from that of their natural grey are
dressed and smoothed down with a steel or iron scraper. The coloring mixture
is sifted on to them dry and rubbed in with a scraper. It consists of mineral coloring
matter, and fine cement in the proportions of 1: 2.
The
The employment of the mixture of color and cement is essential; by this means the
water introduced for the purpose of moistening the mixture of sand is sucked out by
the color, which causes the cement mixed with the sand, and the cement mixed with
the color to set fast, at the same moment and so as to form a continuous mass.
various operations e.g. the moistening of the cement and sand mixture, the pressing
and dressing of the facing-stones as also the sifting and rubbing on of the color,
must take place in immediate sequence. The color put on the facing-stones according
to this method is permanent and weather resisting to such a degree as not to be
altered even by washing with hydrochloric acid.

page_text: When the facing-stones have been colored with the various natural stone colors as
above described, they are removed from the moulds and placed in chambers sheltered
from frost and draught for a period of from 10 to 14 days, during which time their
surfaces are constantly soused with water which causes them to bind thoroughly and
become hard and firm.
If the cenient-facing stones are to be glazed this is done as described below, with
regard to which method it may be remarked beforehand that the process does not
involve the application of heat which the cement cannot withstand as is the case with
articles manufactured from clay, but is conducted in the cold.
The hardened stones after having been well polished and dried in the air are
provided with a glazed-like coating by means of a hairbrush. The goods are by this
means provided with a thoroughly hard and brilliant coloring which is not dis-
tinguishable either in appearance or otherwise from the glaze on earthenware articles.
Its durability with regard to the influences mentioned above is under some circum-
stances superior, the surfaces may be washed with water, and the articles themselves
may be employed for every kind of facing work.
The glaze employed consists of a mixture of preferably about :-
1 litre of alcohol
400 grammes of shellac
10 grammes of Venetian turpentine and
5 grammes of chloride of magnesium,
to which pigment of any desired color is added.
The first three of these ingredients will simply form a species of lacquer or varnish,
and a mixture of them may possibly have been used before, but the last ingredient is
particularly important as it facilitates the coating of the cement with the pigment.
The chloride of magnesium is indeed the substance on which depends the hardness
and durability of the glaze. Owing to the mutual chemical action of the chloride of
magnesium and cement, there forms on the surface of the article a hard crust whereby
the cement is rendered proof against changes of temperature, and the color which is
obtained by mixing a suitable pigment with the glaze, owing to the chemical action
of the various ingredients upon each other, further assists the coating in withstanding
the influences of the atmosphere. A chemical combination taking place between the
material of which the article is made and the coating or glaze, the latter is 1ot liable
to crack and scale off, as it does in ordinary glazed earthenware.
In certain cases this glaze may be replaced by water-glass with which the stones
are coated in a similar manner. The treatment of the stone and the method of
applying the water-glass will in this case be the same as in the instance first
mentioned.
The nature of the glaze may be changed according to the requirements of special
cases and according to the purposes for which the finished article is to be employed
and if it requires a high polish the surfaces may be provided with successive coats of
glaze.
The proportions given are what have been found to produce good results but I do
not bind myself to those precise proportions.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, as communicated to
me by my foreign correspondent, I declare that what I claim is :-
1. The method of manufacturing rough or colored cement-facing-stones by sifting
on to the stones to be colored, immediately after they have been pressed and smoothed
and while they are still moist, a dry mixture of approximately 2 parts cement and
1 part of coloring matter, and rubbing it in with a scraper, after which the stones are
put in a position where they can be soused with water for 10 or 14 days.
2. The method of providing the above mentioned rough and colored cement stones

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with brilliant glaze, consisting in the application, after they have been thoroughly
and carefully smoothed, of a mixture of resin and spirit or only of water-glass
and the application of as many coats as the degree of glaze desired renders
necessary.
Dated this 25th day of January 1890
W. P. THOMPSON & BOULT,
Agents for the Applicant.