An Improved Process for Preserving Wood.
Year: 1899

page_text: Date of Application, 31st Oct., 1899-Accepted, 9th Dec., 1899
COMPLETE SPECIFICATION.
An Improved Process for Preserving Wood.
I, GEORG FRIEDRICHI SEBIODA, of 26, Rue Denfert Rochereau, Boulogne-sur-
Seine, in the Republic of France, Manufacturer, do hereby declare the nature
of this invention and in what manner the same is to be performed, to be parti-
cularly described and ascertained in and by the following statement:―
This invention relates to a process for preserving wood by saturating the same
with a solution of formaldehyde. In this process the formaldehyde forms, with
the albuminous substances already contained in the wood, insoluble compounds
which resist any attacks of insects, and destroy in a thoroughly effective manner
all germs and spores of bacteria and fungi, also worms, insects and their larvæ,
so that wood treated by the present process is permanently protected against
decomposition and decay.
In woods which contain much albumen, a treatment with formaldehyde alone
is sufficient, because the formaldehyde forms insoluble compounds with the
substances contained in the natural sap of the wood. In those woods which
contain too small an amount of albuminous substances and the like, it is on the
other hand necessary to introduce into the wood large quantities of such sub-
stances simultaneously with the formaldehyde. For this object gelose or agar-
agar, also gelatine, and any substanees which contain chondrin or soluble albu-
minous substances are particularly suitable. The saturation of the wood with
the antiseptic liquid may be effected in various ways, for instance, by sprink-
ling, immersion, impregnation under high pressure, or in any other suitable
manner. Those apparatuses which allow of an impregnation of the wood in
the direction of its longitudinal grain are particularly suitable.
By the present invention, albuminous substances and the like contained in the
natural sap of the woods, which, as is well known, form the ground of all
fermentation and décomposition in the same, are not removed from the wood,
but they are actually utilised to form in the wood itself insoluble compounds
with the formaldehyde introduced.
In case a sufficient quantity of such substances does not exist in the natural
sap of any wood, further quantities of the same must be introduced in order to
obtain a sufficient quantity of insoluble compounds in the wood.
The antiseptic liquid employed in the present invention consists, according
to the amount of albumen contained in the wood to be treated, either of a dilute
solution of formaldehyde of to 3%, or a mixture of dilute solutions of formal-
dehyde with gelose (agar-agar) or other substances which contain chondrin or
albumen. These substances are elso employed in proportions of from to 3%.
By using such solutions, substances are formed, after the drying, which contain
the formaldehyde in chemical combination, and which are entirely, insoluble
in water.
The agar-agar or its substitute is dissolved in warm water, and when thoroughly
dissolved, the formaldehyde is added thereto. The solution so obtained may be
used in a cold or in a hot condition. If it be only desired to protect the surface

page_text: of the wood, it is sufficient to sprinkle it or spread the substance thereon with
a brush, but if the wood is to be protected right through, it is immersed in the
liquid, or injectors are employed, the duration of the bath being regulated
according to the constitution of the wood.
The mixture of formaldehyde solution with agar-agar forms a protecting layer
round each fibre of the wood when the layer is dried, which layer is entirely
insoluble in water and resists all microbes or parasites. The woods thus treated
are rendered almost unlimitedly durable, and may in consequence be exposed
to rain, sun or air, or fixed in damp or swampy ground.
The use of agar-agar for introducing the formaldehyde into the wood affords
very especial advantages. The receptive capacity of agar-agar is about ten
times that of gelatine. One portion of agar-agar can absorb 500 parts of water
itself without the mixture becoming liquid at ordinary temperature. A paste
of agar-agar evaporated to dryness obstinately retains a portion of its water.
If formaldehyde be added to a dilute solution of agar-agar, no deposit is at
first formed, but the mass remaining after the evaporation, and which is formed
from the combination with formaldehyde, is a body which is entirely insoluble
in water. If the drying be complete in consequence of prolonged heating
to 110°, the residue will be entirely insoluble. If however the drying be car-
ried out under 100° the residue will apparently be insoluble in water, but in
reality a portion of it gives up the liquid when in a large quantity of water which
absorbs the surplus formaldehyde. Thus the uncombined formaldehyde may be
washed out by large quantities of water, if the washings be continued with
fresh water a thoroughly insoluble residue is finally obtained. For instance if
railway sleepers be saturated with the solution and dried with air or under
moderate heat, the insoluble antiseptic substance is deposited in the pores, which
substance protects the sleepers against any attack of parasites and the like. If
such sleepers be then placed in contact with damp earth, they constantly give
off a portion of the formaldehyde to the latter, so that an antiseptic medium is
formed round the sleeper, which thus forms a second protective layer.
The complete drying of the wood after the saturation is of course necessary
when the wood is intended to lie constantly in water, or when it is to be exposed
to the air, sun and rain.
The herein before described process for preserving wood by saturation with
formaldehyde is cheaper and more effective than the treatment with creosote
and other liquids hitherto employed. The improved process is of very particular
importance for preserving railway sleepers, especially for railway post and tele-
graph appliances: also for ships and marine constructions, vehicles, piles,
foundations for bridges and dams; mining: also posts and railings or frame-
work of all kinds: wood floorings, fencings, wood pipes, and the like. The
use of this improved process is especially valuable for tropical countries, where
wood, otherwise, as is well known is destroyed in a very short time by the
termites or white ants.
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:
1. A process for preserving wood, characterised by the introduction of a
solution of formaldehyde which forms insoluble compounds with the albuminous
substances already contained in the natural sap of the wood, which compounds
resist all attacks of parasites and all germs and spores of bacteria and fungi.
also worms insects and their larvae in a most effective manner, so that the treated
wood is reliably protected against decomposition and decay substantially as
herein before set forth.
2. A modification of the process for preserving wood herein before described
which consists in using a mixture of the dilute solutions of formaldehyde and
gelose (agar-agar) or other like substances which contain chondrin or solu̟ble

page_text: albuminous substances, with the object of obtaining formaldehyde in insoluble
compounds in the wood after the latter has been saturated with the same and
dried. substantially as described.
3. In the process for preserving wood herein before described, the incomplete
drying of the saturated wood, with the object of having a surplus of suitable
formaldehyde in the wood, which is later on gradually imparted by the wood
to the surrounding earth which is in contact with it and forms a layer pro-
|tecting the wood, substantially as described.
Dated this 30th day of October 1899.
WM. P. THOMPSON & Co..
Of 6, Lord Street, Liverpool, Agents for the Applicant.