AN IMPROVED METHOD OF CLEANSING THE OUTSIDE OF BUILDINGS APPLICABLE ALSO FOR CLEANSING SCULPTURES AND THE LIKE
Year: 1884

page_text: I GUILLAUME JOSEPH CONRAD MARIE BARON DE LIEBHABER, Engineer, of
2 Bellevue Terrace Crondance Road, Fulham S.W. London in the county of
Middlesex, do hereby declare the nature of my invention for AN IMPROVED
METHOD OF CLEANSING THE OUTSIDE OF BUILDINGS APPLICABLE ALSO FOR
CLEANSING SCULPTURES AND THE LIKE, to be as follows :—
The invention is an improvement in a former patent, dated September 23d 1881,
and has for its object the cleansing of buildings sculptures and articles of an
architectural character, made of whatever materials natural or artificial, calcareous
or non-calcareous by means of chemical agents acting slightly on the surface of the
stone so as to destroy the adherence of the soiling matter and allow its easy
removal; and I proceed as follows:
When cleansing a building, I apply first, whenever they are found to answer,
acids as described in my former patent; but when I meet parts that are not
readily acted on in this way; I heat the stone before or while applying the acids,
whereby they act more powerfully in less time and with effects not to be obtained
at the ordinary temperature. The stone is heated by means of a blast spirit lamp,
or a jet of gas, or by contact with a hollow metallic body filled with a hot liquid,
or by a radiating or other apparatus. I apply hydrochloric acid by means of a
brush or in a fine jet and where it fails to act, as in the case of a thick carbonaceous
crust, I employ sulphuric acid which is first poured on the stone and then heated to
ebullition, and in some cases nitric acid. In some other cases when the deposit is
of such a nature as to be disaggregated by the mere action of heat, brushing
simply with water, pure or acidulated, will be found sufficient.
When I meet fatty carbonaceous or other deposits which yield with difficulty to
the action of acids or heat or when their action requires to be completed, as is
frequently the case in the sides of buildings most exposed to smoke, I employ a
mixture of quicklime and caustic soda in strong solution in such proportion as to
make a paste easily spread and sufficiently adhering to the wall or stone to be
cleaned. This paste is to remain on the stone some time say 2 or 3 hours after
which it is removed together with the dirty crust which it has detached or severed
from the stone. Instead of caustic soda, I may employ any mixture or paste

page_text: containing or producing soda in a caustic state, or simply a solution of caustic soda
which is then to be applied by means of a brush made of spun glass or other
inorganic substance.
To clean those parts of a building which are made of brick, terra-cotta and some
times other materials, I employ chlorate of potash as follows: I apply to the
surface to be cleaned a very thin layer of that salt either in a fine powder or by
means of a hot solution spread over the surface and allowed to cool. I then direct
on it a jet of gas or the flame of a blast spirit lamp or any radiating or heating
apparatus till the white coating loses its colour by being decomposed and becomes
fluid. I then wash and find that the brick has recovered its pristine colour.
When I meet siliceous stones such as sandstone or granite, I use fluoric acid either
in a liquid state moderately concentrated or in a gazeous state under a covering of
lead or gutta-percha; or by means of a paste made of calcium fluoride finely ground
and sulphuric acid which I spread as a coating over the surface to be cleansed or
bleached and which is to be slightly warmed. The same acid is used on siliceous
and other stones to remove the yellow tint or spots due to the presence or action
of iron.

page_text: OF
I GUILLAUME JOSEPH CONRAD MARIE BARON DE LIEBHABER, Engineer, of
2 Bellevue Terrace, Crondance Road, Fulham S.W. in the county of Middlesex,
do hereby declare the nature of my invention for AN IMPROVED METHOD
CLEANSING THE OUTSIDE OF BUILDINGS APPLICABLE ALSO FOR CLEANSING
SCULPTURES AND THE LIKE and in what manner the same is to be performed,
to be particularly described and ascertained in and by the following statement :-
The invention is an improvement in a former patent dated September 234, 188
and has for its object the cleansing of buildings sculptures and articles of an
architectural character made of whatever materials natural or artificial, calcareous
or non-calcareous, by means of chemical agents acting slightly on the surface of the
stone so as to destroy the adherence of the soiling matter and allow its easy
removal, and I proceed as follows:
1. When cleansing a building or article I apply first, whenever they are found
to answer, acids as described in my former patent; but when I meet parts that are
not readily acted on in this way, I heat the stone before or while applying the
acids, whereby they act more powerfully, in less time, or with effects not to be
obtained at the ordinary temperature.
The stone is heated generally either by a jet of gas or by radiation from gas,
charcoal or coke burning in a portable furnace, or by any other known means:
but when operating on a small surface or on marble and delicate works, I employ
a blast spirit lamp such as is used for sodering or melting old paint; except that
instead of filling the reservoir with alcohol, I fill it with water, so as to have a jet
This last is less liable to
of steam passing over the flame and thence on the stone.
be stained or injured than it would be by a jet of pure alcoholic vapour.
The jet,
however should not be kept steadily on one single point for any length of time,
but be inoved constantly along the surface. Instead of an alcohol-lamp I may use
a gas-lamp.
I apply hydrochloric acid, without admixture of sulphuric acid, by means of
a brush or in a fine jet; and where it fails to act, as in the case of those thick
carbonaceous crusts oft met with on old buildings, I employ sulphuric acid: it is
first poured on the stone and then heated to ebullition, taking care not to let it
entirely dry. In some few cases, I use nitric acid alone or in conjunction with
hydrochloric acid. In some other cases, when the deposit is of such a nature as to
be disaggregated by the inere action of heat, water pure or acidulated will be found
sufficient.
Whatever be the agent resorted to, the dirt set free by its action is to he
removed by a scrubbing brush if still adhering, or by single washing. A strong
jet of water from a pump at a distance is sometimes sufficient.
2. When I meet fatty carbonaceous or other deposits which yield with difficulty
to the action of acids and heat such as are to be found in large towns, owing

page_text: chiefly to organic and other impurities floating in the air, I employ a mixture of
quicklime and caustic soda in strong solution in such proportions as to make
a paste easily spread over and sufficiently adhering to the wall or stone to be
cleansed. The solution should be about 27°, the lime slaked and in fine powder
and so much added by successive portions till the whole well mixed up takes the
consistence of honey. The exact proportions depend however on the nature of the
stone and the state of the atmosphere and may somewhat differ in some cases from
those above. The paste is spread equally over every part of the stone by means
of an iron trowel or spatula, and is to remain on it till the action is complete,
generally two or three hours, after which time it is removed together with the
dirty crust which it has detached or severed from the stone.
The process is
completed by acids and washing.
Instead of this paste, I may employ other mixtures containing or producing soda
in a caustic state. Single liquid caustic soda is used to take off the sulphate of
lime left sometimes on the stone after it has been treated by sulphuric acid which
resists any washing, giving the stone a white tint.
3. To cleanse those parts of a building which are made of bricks, terra-cotta and
sometimes other materials, I employ chlorate of potash as follows:
I apply to the surface to be cleansed a very thin layer of that salt either in a
fine powder or by means of a hot solution spread on the surface and allowed to
cool. I then direct on it a jet of gas or the flame of blast spirit lamp, or any
radiating or heating apparatus, till the whole coating loses its colour and becomes
fluid. I then wash and find that the brick has recovered its pristine colour.
Care should be taken to have the material well dried before, to prevent splitting
by the sudden delatation of the watery particles inside.
To remove certain metallic or other deposits which resist the action of chlorate
alone, such for instance as the reddish crust left on granite after it has been
polished or worked by steel tools and emery powder, I add to the chlorate some
hydrochloric acid either by besprinkling with chlorate powder the parts of the
stone, previously moistened with acid or inversely by pouring hydrochloric acid on
the parts covered with chlorate: I heat till the mass is melted and running in
liquid drops, and I wash with hot water.
4. When I meet siliceous stones or materials such as sandstone granite and
others, I use fluoric acid either in a liquid state moderately concentrated, or in
a gaseous state behind a screen or under a cover of lead or gutta-percha; or I
employ a semi-liquid paste made of calcium fluoride in very fine powder and
sulphuric acid which I spread on the surface to be cleansed or bleached. The
stone is then heated slightly at intervals till the action is completed, and worked.
The action of liquid fluoric acid is enhanced by adding after it has been poured
on the stone, some concentrated sulphuric acid and also by being slightly heated.
The same fluoric acid is used to remove the yellow tint or strain due to the
presence of iron on sanstone and other stones.
Having now particularly described and ascertained the nature of my inven-
tion and in what manner the same is to be performed, I declare that what
I claim is
1. The method of heating the stone by any known means, before or while
applying the acids for the purpose of cleansing, in order to further or facilitate
their action and the particular mode of using for the same purpose a jet of steam
passing over a flame in the manner aforesaid or in any other manner.
2. The use for cleansing buildings and stone articles, of a paste made of caustic
soda and quicklime as aforesaid, or of any mixture containing or producing soda in
a caustic state.
3. The use of chlorate of potash or analogous salts heated to liquefaction as
aforesaid, to cleanse bricks, terra-cotta and other materials; and the addition
of hydrochloric acid to remove certain deposits not acted on by chlorate alone.

page_text: 4. The use for the purpose of cleansing or bleaching sandstone, granit and other
materials containing silica, of fluoric acid either in a gaseous state under cover
or in a liquid state prepared beforehand; its concentration by sulphuric acid when
on the stone; and the use of a paste made of calcium fluoride and sulphuric acid
(or mixtures to the same effect) spread on the stone and heated in the manner
aforesaid.