An Improved Process for Impregnating Fibrous Substances such as Wood, Peat or the like.
Year: 1896

page_text: Date of Application, 10th Nov., 1896
Complete Specification Left, 20th July, 1897-Accepted, 11th Sept., 1897
PROVISONAL SPECIFICATION.
An Improved Process for Impregnating Fibrous Substances such as
Wood, Peat or the like.
A communication by FRITZ HASSELMANN of 106/III Augustenstrasse, Munich in the
Empire of Germany, Architect.
I, WILLIAM PHILLIPS THOMPSON F.C.S., M.I.M.E., of the Agency for Foreign
Patent Solicitors, 6 Lord Street, Liverpool, and 6, Bank Street, Manchester, both in
the County of Lancaster, 118 New Street, Birmingham in the County of Warwick
and 322 High Holborn in the County of Middlesex, Civil Engineer, do hereby declare
the nature of this invention to be as follows:-
In the utilisation of wood for building and working purposes, two properties in
addition to strength have to be considered which determine the choice and treatment
of such wood; these are, the combustibility of the wood and the slow destruction or
deterioration of the same, by damp, combustion, attacks of insects, or the like;
moreover, the wood in consequence of the drying up of the sap contained therein
shrinks in time, warps or splits, and thereby threatens the existence of articles
made therefrom.
Various attempts have been made to remove those properties of wood which
deleteriously affect its use, but none of the means hitherto employed have sufficed
to remove all these drawbacks, and people have had to remain content with the
removal of certain of these properties corresponding to the actual purposes at the
moment, but in doing this, care has also to be taken as to the kind of wood
employed for the special purpose.
Wood contains a series of tubes for receiving and circulating the sap, which tubes
are narrower or wider, closer or more open, according to the nature of the wood, and
they thereby impart to the wood its hardness and solidity.
The sap of the wood circulates in these tubes, and in different trees is more
watery, oily or resinous and contained in larger quantities at certain seasons of the
year, whilst at other seasons it is less in quantity.
The quantity and constituency of this sap in the wood determines the durability
and power of resistance of the same against decay.
Experience has shown that close (hard) woods, have great durability and that
woods with a resinous sap resist decomposition and decay very well.
Even the time at which the timber is felled has to be considered from the point
of view of durability, and it has been found that trees which are felled at a time
when the sap is scanty, that is to say in autumn and winter, afford a much more
durable and sounder wood.
The present invention has for its object a process as already mentioned to remove
the properties of wood which affect its durability and solidity, and to render the
wood incombustible.and unsusceptible to chemical decomposition, and also to increase
its solidity, and at the same time render it possible to utilise for building and

page_text: wood-working purposes, woods of otherwise low value which have hitherto not been
able to be used for these purposes.
For this purpose the wood is preferably successively impregnated with two
solutions, which combine to form a solid substance, and in this manner fill up the
pores and cells of the wood, after they have expelled the easily decomposable 'saps,
which mainly effect the destruction of the wood by decomposition.
Whilst, speaking generally, any wood is suitable for this purpose (and any sound.
wood of normal structure and toughness is suitable for receiving the impregnating
substance), the impregnation may be effected more easily and rapidly in less dense
(soft) woods, which are preferably felled when full of sap, and the sap of which is
more watery than resinous, and thus these woods which are at present of less value
on account of these properties, are by this process converted into useful and durable
material.
As the impregnation of the wood necessitates previous removal of the wood sap,
it is recommended that the impregnation should be effected as soon as possible after
the felling of the trees in order to prevent the wood sap (more particularly in the
case of resinous timbers) from hardening, and thus presenting difficulties to its
removal.
A further means for facilitating this operation consists in forming in the tree
which is to be felled, a short time before the felling, a groove of 6 to 8 centimetres
in depth and about 30 to 35 centimetres from the ground, so that by means of
this groove in a natural manner, a considerable quantity of the sap is removed from
the wood.
All those substances which form with one another a solid deposit, and do not
attack or dissolve cellulose are suitable for the impregnating.
The following combinations have been found particularly suitable :-
Copperas and chloride of calcium;
Chloride of zinc and caustic baryta;
Copperas and caustic baryta;
Chloride of zinc and chloride of calcium;
Caustic baryta and chloride of calcium.
The two substances may be either employed separately in succession, or
simultaneously in a mixed condition, two parts of the first being employed to three
parts of the second substance.
These proportions of mixture however may be modified to suit the constitution of
the wood which is to be impregnated, and the successive or simultaneous use of the
two substances may be determined by the object to which the impregnated wood is
to be applied as well as the depth or extent of the impregnation.
According to the depth to which it is intended to take place, the impregnation
may either be effected by pumping out the air and sap contained in the wood in order
to facilitate the admission of the impregnating fluid into the very interior of the
same, or the wood may be simply placed in a suitable bath, and the impregnating
fluid be allowed to penetrate it.
In the first case the wood which is to be impregnated may be placed in the first
solution, for instance copperas, and the air removed by means of an air pump.
The air, sap, and resin, contained in the wood are then drawn out, and in their
place the solution enters into the pores and cells.
When the piece of wood has absorbed sufficient of this first solution, it is removed
from the bath and dried for about one hour in a moderate heat, and then placed in
the second solution, for instance, chloride of calcium, and there subjected to a similar
treatinent by means of an air pump.
The cells of the wood are also thereby filled with this solution.
After the wood has been sufficiently saturated with the second solution, and dried,
a solid insoluble thick cement is formed from the salts contained, the chemical
composition of this cement depending on the substances selected. This cement filla

page_text: all the pores of the wood and imparts thereto the power of resistance to fire, decay,
etcetera, and in consequence of the removal of the sap, prevents it warping, splitting,
or being otherwise essentially affected by the action of time.
Even if by this impregnation the wood has increased in denseness and hardness,
this circumstance in the present condition of wood-working is of secondary
importance, as the wood remains still capable of being treated with any ordinary
tools, and is also capable of being polished, and the impregnation may even be
effected in the case of carved wood after the same has been carved.
If instead of impregnation by means of an air pump, the wood be only treated in a
bath, the first solution is employed hot, and the second solution in which the wood
impregnated with the first solution is directly immersed from the former is employed
in a cold condition.
The impregnation of peat and more particularly compressed peat, takes place in a
similar manner, the choice of the substances to be employed being determined by
the kind of peat and the object for which the articles made therefrom are to be
employed.
The impregnating materials may also be mixed with the peat material in a cold
condition after the latter has been disintegrated and cleaned and before it is brought
into the pressing apparatus.
For impregnating long trunks (telegraph poles, masts, beans, standards, etcetera)
tightly closed vessels of suitable length and sufficient capacity (resembling retorts)
are filled with the wood which is to be impregnated and the sap and air are
preferably first removed from the wood by means of an air pump driven by a motor
and the first solution is then admitted, the remainder thereof, when the wood has
been saturated, being run off and the second solution admitted.
In both cases impregnation is supported by the action of the air pump.
When the second solution has been run off, the wood is dried, whereupon the
forination of the cement takes place.
Such impregnated woods in addition to being employed for building purposes,
telegraph poles, staircases, furniture, etcetera, may with success be employed (as
also may the compressed peat) for forming blocks for noiseless pavements, in which
case, in addition to their solidity and capability of resistance to decay, etcetera, their
impenetrability to water and their being unaffected by moisture and other impurities,
render these impregnated woods very suitable.
Other suitable fibrous substances may in a similar way be rendered incombustible
and inore durable by this impregnation process.
A further modification of this process consists in subjecting the woods successively
to the action of two liquids, which action in both cases is supported by boiling the
wood in the said liquids. The wood is first boiled in a mixture of copperas and
sulphate of alumina of 1:30 after which it is treated in a similar way with chloride
of calcium 1: 50 with an addition of caustic lime of 1:40. By the boiling
together of caustic lime and chloride of calcium, the wood is caused to dry very
rapidly and to remain in this condition, whilst by the use of chloride of calcium
without caustic lime the wood remains hygroscopic.
This process may be carried out either after the wood has been previously extracted
or otherwise freed in a suitable manner from the contents of its cells, the boiling in
the liquids being carried out under pressure, or the preliminary treatment of the
wood inay be entirely omitted. In the latter case the air pressure may be dispensed
with, so that the plant necessary therefore is not required.
It is however to he recommended, when circumstances allow it, to let the wood
before being boiled remain a considerable time in the first but cold liquid in copperas
in order to absorb the same so that this latter shall penetrate into the wood, by which
means the boiling process, which otherwise endures for each mixture 3-4 hours, may
be reduced to a duration of 2-24 hours. Generally speaking, the duration of the
boiling process cannot be fixed precisely, as it depends on the nature of the wood
and differs for different kinds of wood, but for deciduous woods, more particularly,

page_text: such as beeches, alder and birch, less time is required than for coniferous or pine
trees.
Wood treated by the process herein before described is thoroughly filled by the
liquids which combine in the same to form a solid body and thereby to a certain
extent petrify the wood without essentially altering the capabilities of treatment of
the same. The wood is rendered non-inflammable and its durability and power of
resistance is increased. It is also rendered resistant to the formation of mould, the
attacks of insects and decay. This must be ascribed to the circumstance that either
the substances producing decay (the material filling the cells) are removed, or that
these substances are chemically changed by the boiling in the presence of salt
solutions in such a way as to combine with these to form a solid body so that the
conditions for producing decay or formation of mould no longer exist.
Dated this 9th day of November 1896
An Improved Process for Impregnating Fibrous Substances such as
Wood, Peat or the like.
A communication by FRITZ HASSELMANN of 106/III Angustentrasse, Munich, in the
Empire of Germany, Architect.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of the Agency for Foreign Patent
Solicitors, 6 Lord Street, Liverpool, and 6, Bank Street, Manchester, both in the
County of Lancaster, 118 New Street, Birmingham in the County of Warwick and
322 High Holborn in the County of Middlesex, Civil Engineer, 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:-
In the utilisation of wood for building and working purposes, two properties in
addition to strength have to be considered which determine the choice and treatment
of such wood; these are, the combustibility of the wood and the slow destruction or
deterioration of the same, by damp, combustion, attacks of insects, or the like;
moreover, the wood in consequence of the drying up of the sap contained therein
shrinks in time, warps or splits, and thereby threatens the existence of articles made
therefrom.
Various attempts have been made to remove those properties of wood which
deleteriously affect its use, but none of the means hitherto employed have sufficed
to remove all these drawbacks, and people have had to remain content with the
removal of certain of these properties corresponding to the actual purposes at the
moment, but in doing this, care has also to be taken as to the kind of wood employed
for the special purpose.
Wood contains a series of tubes for receiving and circulating the sap, which tubes
are narrower or wider, closer or more open, according to the nature of the wood, and
they thereby impart to the wood its hardness and solidity.
The sap of the wood circulates in these tubes, and in different trees is more watery,
oily or resinous and contained in larger quantities at certain seasons of the year,
whilst at other seasons it is less in quantity.
The quantity and constituency of this sap in the wood determines the durability
and power of resistance of the same against decay.

page_text: Experience has shown that close (hard) woods, have greater durability and that
woods with a resinous sap resist decomposition and decay very well.
Even the time at which the timber is felled has to be considered from the point of
view of durability, and it has been found that trees which are felled at a time when
the sap is scanty, that is to say in autumn and winter, afford a much more durable
and sounder wood.
The present invention has for its object a process as already mentioned to remove
the properties of wood which affect its durability and solidity, and to render the
wood incombustible and unsusceptible to chemical decomposition, and also to increase
its solidity, and at the same time render it possible to utilise for building and wood-
working purposes, woods of otherwise low value which have hitherto not been able to
be used for these purposes.
For this purpose the wood is preferably successively impregnated with two solutions,
which combine to form a solid substance. and in this manner fill up the pores and
cells of the wood, after they have expelled the easily decomposable saps, which mainly
effect the destruction of the wood by decomposition.
Whilst, speaking generally, any wood is suitable for this purpose (and any sound
wood of normal structure and toughness is suitable for receiving the impregnating
substance), the impreguation may be effected more easily and rapidly in less dense
(soft) woods, which are preferably felled when full of sap, and the sap of which is
more watery than resinous, and thus these woods which are at present of less value
on account of these properties, are by this process converted into useful and durable
material.
As the impregnation of the wood necessitates previous removal of the wood sap, it
is recommended that the impregnation should be effected as soon as possible after the
felling of the trees in order to prevent the wood sap (nore particularly in the case
of resinous timbers) from hardening, and thus presenting difficulties to its
removal.
A further means fór facilitating this operation consists in forming in the tree which
is to be felled, a short time before the felling, a groove of 6 to 8 centimetres in
depth and about 30 to 35 centimetres from the ground, so that by means of this
groove in a natural manner, a considerable quantity of the sap is removed from
the wood.
All those substances which form with one another a solid deposit, and do not
attack or dissolve cellulose are suitable for the impregnating.
The following combinations have been found particularly suitable :-
Copperas and chloride of calcium;
Chloride of zinc and caustic baryta;
Copperas and caustic baryta;
Chloride of zinc and chloride of calcium;
Caustic baryta and chloride of calcium.
The two substances may be either employed separately in succession, or simul-
taneously in a mixed condition, two parts of the first being employed to three parts of
the second substance.
These proportions of mixture however may be modified to suit the constitution of
the wood which is to be impregnated, and the successive or simultaneous use of the
two substances may be determined by the object to which the impregnated wood is
to be applied, as well as the depth or extent of the impregnation.
According to the depth to which it is intended to take place, the impregnation
may either be effected by pumping out the air and sap contained in the wood in
order to facilitate the admission of the impregnating fluid into the very interior of the
same, or the wood may be simply placed in a suitable bath, and the impregnating
fluid be allowed to penetrate it.
In the first case the wood which is to be impregnated may be placed in the first
solution, for instance copperas, and the air removed by means of an air pump.

page_text: The air, sap, and resin, contained in the wood are then drawn out, and in their
place the solution enters into the pores and cells.
When the piece of wood has absorbed sufficient of this first solution, it is removed
from the bath and dried for about one hour in a moderate heat, and then placed in the
second solution, for instance, chloride of calcium, and there subjected to a similar
treatment by means of an air pump.
The cells of the wood are also thereby filled with this solution.
After the wood has been sufficiently saturated with the second solution, and dried,
a solid insoluble thick cement is formed from the salts contained, the chemical
composition of this cement depending on the substances selected. This cement fills
all the pores of the wood and imparts thereto the power of resistance to fire, decay,
etcetera, and in consequence of the removal of the sap, prevents it warping, splitting,
or being otherwise essentially affected by the action of time.
Even if by this impregnation the wood has increased in denseness and hardness,
this circumstance in the present condition of wood-working is of secondary importance,
as the wood remains still capable of being treated with any ordinary tools, and is also
capable of being polished, and the impregnation may even be effected in the case of
carved wood after the same has been carved.
If instead of impregnation by means of an air pump, the wood be only treated in a
bath, the first solution is employed hot, and the second solution in which the wood
impregnated with the first solution is directly immersed from the former is employed
in a cold condition.
The impregnation of peat and more particularly compressed peat, takes place in a
similar manner, the choice of the substances to be employed being determined by the
kind of peat and the object for which the articles made therefrom are to be
employed.
The impregnating materials may also be mixed with the peat material in a cold
condition after the latter has been disintegrated and cleaned and before it is brought
into the pressing apparatus.
For impregnating long trunks (telegraph poles, masts, beams, standards, etcetera)
tightly closed vessels of suitable length and sufficient capacity (resembling retorts)
are filled with the wood which is to be impregnated and the sap and air are preferably
first removed from the wood by means of an air pump driven by a motor and the first
solution is then admitted, the remainder thereof, when the wood has been saturated,
being run off and the second solution admitted.
In both cases impregnation is supported by the action of the air pump.
When the second solution has been run off, the wood is dried, whereupon the
formation of the cement takes place.
Such impregnated woods in addition to being employed for building purposes,
telegraph poles, staircases, furniture, etcetera, inay with success be employed (as also
may the compressed peat) for forming blocks for noiseless pavements, in which case,
in addition to their solidity and capability of resistance to decay, etcetera, their
impenetrability to water and their being unaffected by moisture and other impurities,
render these impregnated woods very suitable.
Other suitable fibrous substances may in a similar way be rendered incombustible
and more durable by this impregnation process.
A further modification of this process consists in subjecting the woods successively
to the action of two liquids, which action in both cases is supported by boiling the
wood in the said liquids. The wood is first boiled in a mixture of copperas and
sulphate of alumina of 1:30 after which it is treated in a similar way with chloride
of calcium 1:50 with an addition of caustic lime of 1:40. By the boiling together
of caustic lime and chloride of calcium, the wood is caused to dry very rapidly and
to remain in this condition, whilst by the use of chloride of calcium without caustic
lime the wood remains hygroscopic.
This process may be carried out either after the wood has been previously extracted
or otherwise freed in a suitable manner from the contents of its cells, the boiling in
the liquids being carried out under pressure, or the preliminary treatment of the

page_text: wood may be entirely omitted. In the latter case the air pressure may be dispensed
with, so that the plant necessary therefor is not required.
It is however to be recominended, when circumstances allow it, to let the wood
before being boiled remain a considerable time in the first but cold liquid in copperas
in order to absorb the same so that this latter shall penetrate into the wood, by which
means the boiling process, which otherwise endures for cach mixture 3-4 hours, may
be reduced to a duration of 2-24 hours. Generally speaking the duration of the
boiling process.cannot be fixed precisely, as it depends on the nature of the wood
and differs for different kinds of wood, but for deciduous woods, more particularly,
such as beeches, alder and birch, less time is required than for coniferous or pine
trees.
Wood treated by the process hereinbefore described is thoroughly filled by the
liquids which combine in the same to form a solid body and thereby to a certain
extent petrify the wood without essentially altering the capabilities of treatment of
the same. The wood is rendered non-inflammable and its durability and power
of resistance is increased. It is also rendered resistant to the formation of mould,
the attacks of insects and decay. This must be ascribed to the circumstance that
either the substances producing decay (the material filling the cells) are removed, or
that these substances are chemically changed by the boiling in the presence of salt
solutions in such a way as to combine with these to form a solid body so that the
conditions for producing decay or formation of mould no longer exist.
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. Process for impregnating fibrous substances eg. wood and peat etcetera,
characterised by the air, juices and resins etcetera contained in the fibrous substances
being removed from the same and the latter impregnated successively or simul-
taneously with several suitable solutions, adapted to combine in the pores and cells
of the fibrous materials in an insoluble firm mass filling the whole of the cells
substantially as hereinbefore set forth.
2. In the herein described process for impregnating fibrous substances, the use
successively or simultaneously of copperas and chloride of calcium or chloride of zine
and caustic baryta or copperas and caustic baryta or caustic baryta and chloride of
calcium substantially as described.
3. A method of carrying out the herein described process for impregnating fibrous
substances characterised by the fibrous materials after the air and juices etcetera have
been pumped out being impregnated by the use of the air pump with the one
solution and then with the other or with a mixture of both solutions while in the
cold state substantially as described.
4. A method of carrying out the herein described process for impregnating fibrous
substances, characterised by the fibrous substances being impregnated without the
use of an air pump by being first placed in a bath of the first solution whilst the
latter is boiling hot, and then in order to be cooled down being placed in the second.
solution whilst the latter is cold substantially as described.
5. A method of carrying out the herein described process for impregnating fibrous
substances characterised by a lengthy boiling (according to the kind of wood) of the
wood first in a mixture of copperas and sulphate of alumina 1:30, then in chloride of
calcium 1:50 with an addition of caustic line 1:40, the walls of the cells and any
substances still existing therein (protoplasmic material) being impregnated,
substantially as described.
6. A method of carrying out the berein described process for impregnating fibrous
substances, in which the wood to be impregnatel is first extracted and freed from
the material with which its cells are filled and then boiled under air pressure,
substantially as described.
7. In the herein described process for impregnating fibrous substances, placing the

page_text: wood before boiling in the first liquid mixture (copperas and sulphate of alumina)
substantially as described.
Dated this 19th day of July 1807
W. P. THOMPSON & Co.,
Agents.