A NEW METHOD OF RENDERING CLOTH, WOOD, PAPER AND THE LIKE, WATER-PROOF BUT NOT AIR- TIGHT
Year: 1884

page_text: I NILS ALEXANDER ALEXANDERSON, of Stockholm, in the Kingdom of Sweden,
Engineer, do hereby declare the nature of my invention for "A NEW METHOD OF
RENDERING CLOTH, WOOD, PAPER AND THE LIKE, WATER-PROOF BUT NOT AIR-
TIGHT "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 this invention is to prepare cloth, wood, paper and the like in
a simple, practical and inexpensive way, to render them water-proof but not
air-tight.
This operation is based upon the well known quality of plant and animal fibres
of decomposing certain salts, particularly those of aluminium, the base, alumina or
a basic salt, being taken up by the fibres and firmly adhering to them, thereby
preventing water from moistening the fibres, which are thus incapable of absorbing
it. This circumstance gave the idea of making cloth impermeable to water, allowing
at the same time free access to the air.
On this account also it is possible to give cloth a certain degree of impermeability
by the decomposition of acetate of lead by alum or sulphate of alumina, whereby
the acetate of alumina is obtained, in the solution of which the cloth was submerged
for a longer or shorter time, and then, without any previous rinsing, subjected to
the air for a long time to be dried.
An improvement on this method was to give the cloth, thus impregnated and
dried, a subsequent rinsing in a soap solution, whereby a soap of alumina was
formed, which in depositing upon the cloth stuck to it, and, after the rinsing off
the superfluous soap and the drying of the cloth, imparted to it the property of
impermeability.
The application that cloth, dressed in this manner, has received, has been rather
insignificant and has been confined to superior woollen stuffs, probably on account
of the imperfection of the mode of impregnation.
A good and inexpensive impermeable cloth, which at the same time permits the
free passage of the air, being in many respects of the utmost importance, I have
devoted a long time to the study of the subject and have arrived at the following
result, constituting a simple and sure solution of this question.

page_text: Salts of aluminium, as alum, sulphate and acetate of alumina act in solution as
acids, and as the alumina of such a solution depositing on the fibres is soluble in
acid liquids, and as the base-depriving capacity of the fibres must increase the
degree of acidity in the solution, it is evident that the increased acid property of
the solution must still more counteract the faculty of the fibres of binding the
alumina to them, thus this property will either, as in the case of cotton and linen,
not be maintained, or, as in the case of woollens, if at all, only in an incomplete
degree, and thus the impregnation as to watertightness will be imperfect and even
then confined to animal fibres.
Consequently, to deprive the salts of their acid property, so injurious to the
impregnation, and thus to increase the capacity of the fibres to appropriate alumina,
must be a very essential improvement in the use of salts of aluminium for the
impregnation, and surpasses any previous method.
This result I have attained by using the basic-salts instead of the solution of
alum, sulphate and acetate of alumina acting as acids.
The composition of these salts varies. I will here, however, give some typical
formulæ of the same compared with the salts, formerly used for the impregnation
and which have the qualities of acids.
Al² V₂ 3 PV₂ + C& O₂ F¹₂ = C.
Sulphate of alumina. Hydrate of lime.
Slacked lime.
₂ DU₂ + Alg50, H₂
Gypsum.
Basic salt.
If I want to have an alkaline solution of a basic-salt or to prevent more certainly
a basic-salt from depositing prematurely, I may add some tartaric acid, citric acid,
glycerine or any other matter having this property.
.
The important property possessed by the solution of those basic-salts of depositing
basic-salts at its heating or diluting is also of very great importance for the
impregnation, as these "in statu nascenti" deposited basic-salts are easily absorbed
by the cloth.
I also use for the impregnation the aluminate of soda having very much the
quality of a basic-salt and its quality of depositing alumina by the influence of
acids,
The basic chromium salts and the basic iron salts, produced in the same manner,
I also make use of for the impregnation as they in some degree behave to the fibres
in the same manner as the aluminium salts,

page_text: The method which I use for preparing water-proof but not air-tight cloth, paper,
wood and the like is very simple. The material is steeped in a cold or hot solution
of one or more of the above described basic-salts. The strength of the solution and
the time required for the impregnation is dependent upon the nature of the material
to be impregnated. The material is rinsed in water and then rapidly dried, when
it has obtained impermeability in the highest degree. The rinsing is of greatest
importance as it partly removes soluble salts and partly deposits basic-salts in the
cloth.
Some cloths do not require any rinsing but are dried directly.
Cloths which are difficult to steep in the impregnating liquid are preferably first
well soaked in water.
The impermeability is also effected, according to this invention, by depositing
"in statu nascenti" the basic-salts in the cloth, so that the cloth is impregnated
with neutral or basic salts of aluminium, and then with or without previous drying
passed through a solution of the neutralizing material, for instance carbonate of
soda, or that the cloth is first impregnated with the neutralizing material and then
passed through the solution of the neutral or basic salt of aluminium. The cloth
is then rinsed and dried.
The cloth impregnated in one or other of the ways described has the following
advantages, that is to say :-It obtains, in a high degree, the property of imper-
meability; its price will be enhanced but very little; it will not be attacked by
moths; its colours will be fixed and will not change by the impregnation; it
permits the passage of the air, which is of great importance in sanitary respects;
no poisonous matters are instilled through the impregnation; and it does not lose
its impermeability or its resistance against moths by being worn or being laid away
for a long time.
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
The method hereinbefore described of rendering cloth paper and the like water-
proof and unliable to attack by moths either (1st) by impregnating the said
substances with basic salts of aluminium, iron or chromium; (2nd) by impregnating
the said substances with salts of aluminium, iron or chromium, and thereafter, with
or without previous drying, treating with the neutralizing materials or (3rd) by
impregnating the said substances with a solution of the said neutralizing materials
and thereafter, with or without previous drying, treating with aluminium, iron-or
chromium-salts; or 4th by treating the said substances according to two or more of
the above mentioned alternatives.
HASELTINE, LAKE & Co.,
For the Applicant.