Improvements in Treating Wood for the purpose of Rendering it Non-inflammable or for Preserving it.
Year: 1897

page_text: PROVISIONAL SPECIFICATION.
Improvements in Treating Wood for the purpose of Rendering it
Non-inflammable or for Preserving it.
I, HENRY VALENTINE SIMPSON, of 15, Auckland Road, Upper Norwood, in the
County of Surrey, Lieutenant in the Royal Navy, do hereby declare the nature of
this invention to be as follows; -
The most successful recent methods employed for the impregnation of wood
by various bodies for the purpose of rendering it non-inflammable or of preserving
it, have a common object, that is, to exhaust the air from the pores of the wood,
and to present to the wood when in that condition, a solution containing the
desired fireproofing or preservative ingredients. The pores of the wood being
empty suck up the solution. The water of the solution is then dried off either
with applied heat or not, leaving the fireproofing or preservative ingredients in
the wood.
The success of the operation depends on the more or less perfect exhaustion
of the air and moisture and also on the natural character of the wood.
In such woods as Weymouth pine and ash for instance, impregnation has been
effected to the depth of over 4 inches but in such woods as spruce, teak, pitch pine &c.
the extent of the impregnation is found to be of a more variable character.
Now the object of my invention is to treat wood of all classes so that thorough
impregnation of the same can be effected.
I effect this partly by means of a preliminary process or treatment.
It is obvious that if the pores of the wood are open so that all the air and mois-
ture can be exhausted, the solution on being then admitted will take the place
of the air and so impregnate the wood.
Now the resin in resinous woods, the oil in oily woods and the closeness or block-
ing of the pores in various other woods prevent a proper exhaustion of the air,
and therefore a proper impregnation and it is the object of my preliminary pro-
cess to prepare these woods for the impregnation.
For the purpose of my preliminary process I place the wood to be treated in
an air tight receptacle, and exhaust the air and vapours from the pores as much
as possible, preferably under moist heat, then in the case of wood containing
little or no resin or oil, I admit water, preferably cold, so as to cover the wood,
the vacuum being maintained as long as possible. The result is that the water
penetrates the pores of the wood. I then apply pressure to enforce the action,
(and the water may now be heated) until the wood has taken up as much water
as it can. The water is then removed and the wood dried, either in the air or
by any of the known methods.
The effect of water on wood is to dissolve a certain part of its fermentable and
solvent constituents. On the water being dried off, the wood is left in a more
porous condition and therefore more amenable to the second process or impregna-
tion of the preserving or fireproofing ingredients, the wood also becomes less
liable to rot and more free from cracking and warping. In certain cases as for

page_text: instance when the wood is of thin dimensions or is naturally porous I may steep
it in water instead of subjecting it to exhaust or vacuum treatment as above
described.
In the case of oily woods such as teak, I may render the water alkaline with
soda or potash or the like so as to cause a saponification of the oil which the water
will dissolve out and thus leave the pores more open.
In the case of resinous woods I may use if necessary in the place of water a
solvent of resin such as methylated spirit so as to dissolve the resin and leave the
pores clear.
The preliminary process being completed and the wood dried, it is then fit
for the impregnation process, but it is not necessary that the latter should follow
at once.
The same appliances used for the preliminary process can be used for the
impregnation.
For the purpose of impregnating the wood I place it. under exhaust and if
necessary heat, until all the air and moisture are exhausted. Too dry a heat is
not desirable.
The solution to be used is then submitted to the wood still under vacuum.
The solution should preferably be cold so as to prevent as much as possible the
formation of vapor which would be sucked up by the wood and so prevent prefect
penetration of the solution.
The solution should also be denuded of air before entering the air tight recep-
tacle for the same reason, namely, to prevent air entering the pores of the wood.
The solution should be submitted to the wood so as to cover it as quickly as
possible in order to avoid the wood taking up the vapor formed, which naturally
would not contain the ingredients.
Any air bubbles or matter which form on the surface of the wood when in the
receptacle under exhaust may be removed by suitable devices and the position of
the wood may also be altered in order to facilitate the exhaustion of the air, and
this without opening the air tight receptacle or breaking the vacuum. The solu-
tion having been run in as above described, pressure may be applied so as to assist
the impregnation. When the wood is sufficiently saturated the solution is drawn
off and the wood dried. It may be that continuous boiling of the wood in the
solution for a prolonged period would cause eventual impregnation but this would
be at the cost of the color, strength and durability of the wood.
My preliminary process leads to the same result without the drawbacks.
For the purpose of impregnation I may use salts such as phosphate of ammonium
dissolved in water, and rendered neutral if necessary or 1 may use soluble silicate
of soda or lime or boracic acid or borax or I may use any one or more of these
bodies combined with phosphate of ammonium or I may use phosphate of
ammonium together with sulphate of iron or copper and with bichloride of
mercury for protection against germs and worms &c. In cases where it is
necessary to guard against the after absorption of moisture I may
use another vehicle of impregnation than water which will dissolve
the necessary ingredients and evaporate. In this case less hygroscopic
ingredients can be used or I may place the wood after treatment for a short time
in solution of sulphate of iron or copper or the like which will harden the sur-
face and prevent absorption of moisture. This method is preferable in the case
of wood that is not required to undergo much working after treatment such as
piles, sleepers, rafters, joists &c. In the case of wood that will be considerably
worked up atterwards I prefer to use ingredients as little liygroscopic as possible
while still possessing preserving and fire proof qualities and to cover the wood
after a thorough drying with a thin coat of shellac or copal. Complete drying
is important as the least heart moisture will burst through, under the influence
of heat and crack the surface and on evaporation will leave a fine crust or powder
composed of the ingredients used. For this reason slow drying is preferable.
In the case where the after use of the wood renders it necessary to guard against

page_text: absorption of moisture and the consequent corrosion of metals in contact with it
such as nails, I may incorporate with the fireproofing ingredients a certain amount
of some substance such as size which will materially assist in the object aimed at.
As it is important that the solution be presented to the wood in the receptacle
as speedily as possible I may cause the solution to be run into the receptacle in
many places so as to cover the wood in the shortest possible time, or I may, after
the pores of the wood are exhausted, partially fill the receptacle with cold solu-
tion from the bottom and either gradually cause the solution to rise over the wood
while the partial vacuum is maintained or I may use a suitable mechanical device
whereby the load of wood may be suddenly immersed in the solution, while the
pores are still in a state of exhaustion.
It is obvious that the treatment must vary according to the description of wood
and according to the eventual use of the wood, whether for piles, sleepers or for
carpenters' and joiners' use.
It may happen that impregnation to a certain depth only is required, in which
case I may of course vary the duration of treatment and the preliminary treat-
ment may not be necessary.
It is not essential though I consider it very important except in the case of
thin wood or of easily impregnated wood to submit the wood to my preliminary
treatment before the impregnation process, that is to say, the latter process can
be followed without my preliminary treatment.
Dated this 7th day of December 1897.
J. C. MEWBURN & ELLIS,
55 and 56, Chancery Lane, London, Chartered Patent Avents.
Improvements in Treating Wood for the purpose of Rendering it
Non-inflammable or for Preserving it,
I, HENRY VALENTINE SIMPSON, of 15, Auckland Road, Upper Norwood, in the
County of Surrey, Lieutenant in the Royal Navy, do hereby declare the nature
of the said invention and in what manner the same is to be performed to be
particularly described and ascertained in and by the following statement:-
The most successful recent methods employed for the impregnation of wood
by various bodies for the purpose of rendering it non-inflammable or of preserv-
ing it, have a common object, that is, to exhaust the air from the pores of the
wood, and to present to the wood when in that condition, a solution containing
the desired fireproofing or preservative ingredients. The pores of the wood being
empty suck up the solution. The water of the solution is then dried off, either
with applied heat or not, leaving the fireproofing or preservative ingredients in
the wood.
The success of the operation depends on the more or less perfect exhaustion
of the air and moisture, and also on the natural character of the wood.
In such woods as Weymouth pine and ash for instance, impregnation has been
effected to the depth of over four inches, but in such woods as spruce, teak, pitch
pine &c. the extent of the impregnation is found to be of a more variable character.
Now the object of the present invention is to treat wood of all classes so that
thorough impregnation of the same can be effected.
This is effected partly by means of a preliminary process or treatment.
It is obvious that if the pores of the wood are open so that all the air and
moisture can be exhausted, the solution on being then admitted will take the place
of the air and so impregnate the wood.

page_text: Now the resin in resinous woods, the oil in oily woods and the closeness or
blocking of the pores in various other woods, prevent a proper exhaustion of
the air, and therefore a proper impregnation, and it is the object of the preliminary
process to prepare these woods for the impregnation.
For the purpose of the preliminary process the wood to be treated is placed in
an air-tight receptacle capable of withstanding considerable pressure, and adapted
to be put into communication with an air pump which can maintain a vacuum
in the receptacle of about 28 barometric inches, and with a steam supply.
Apparatus of this kind is well understood and requires no further description.
The wood is first brought to a condition of moist heat, and this can be advan-
tageously effected by steaming it to a greater or less extent according to its nature
and description, at a temperature which should not, however, exceed 200° to
212° F. Then while the wood is in the condition of moist heat the air and vapors
are exhausted from the pores as such as possible, and while the wood is still under
exhaust there is admitted a solvent agent to open up the pores and dissolve out a
certain part of the soluble and fermentable constituents of the wood. For general
purposes, it is preferred in the case of wood containing little or no resin to employ
water as the solvent; the water may be run in on to the wood while this is under
exhaust, or it may be applied in the state of low temperature vapor, or of atomised
spray, or vapor and atomised spray may be employed together. The vapor or
atomised water or both combined will be employed when time is a matter of
importance, since if the wood be impregnated with water longer time is required
to dry it, whereas if it has a less proportion of water in it as in the case of spray
it can be dried more quickly.
When water in the mass is employed it is run in preferably cold so as to cover
the wood, the vacuum being maintained as long as possible. The result is that
the water penetrates the pores of the wood. Pressure is then preferably applied
to enforce the action (and the water may now be heated) until the wood has taken
up as much water as it can. When the solvent action has proceeded sufficiently
far, the water is run off, and the wood more or less dried, either in the air or by
any of the known methods.
This drying is highly desirable, because the drying clears the pores leaving
the wood more amenable to the main process.
If water vapor or spray has been employed as the solvent agent, the wood may
be sufficiently dried by exhaust without necessity for removal from the receiver
between the preliminary and impregnating processes, and when time is a matter
of importance this is a great advantage; if however water in the mass has been
used as the solvent it is desirable to remove the wood from the receiver and dry
it in a kiln or the like, preferably slowly to avoid warping and checking.
The effect of water on wood is to dissolve a certain part of its fermentable and
soluble constituents. On the water being dried off the wood is left in a more
porous condition and therefore more amenable to the second process or impreg-
nation of the fireproofing or preserving ingredients; the wood also becomes less
liable to rot and more free from cracking and warping.
In the case of oily woods such as teak, the water may be rendered alkaline with
soda or potash or the like, so as to cause a saponification of the oil which the
water will dissolve out and thus leave the pores more open.
In the case of resinbus woods there may be used if necessary in the place of
water a solvent of resin such as methylated spirit, so as to dissolve the resin and
leave the pores clear: the expense of using such a solvent militates somewhat
against the use of it.
The preliminary precess being complete and the wood dried as above described
to a sufficient extent, it is then ready for the impregnation, but it is not necessary
that the latter should follow at once.
The same appliances used for the preliminary process can be used for the impreg
nation.
For the purpose of impregnating the wood it is placed under exhaust, and if

page_text: necessary heated until the air and moisture are exhausted. Too dry a heat is not
desirable and it is therefore preferred to subject the wood in the receiver to alter-
nate steaming and exhaust, which may be repeated as often as desired.
The impregnating. solution to be used is then admitted to the wood still under
vacuum. The solution should preferably be cold, so as to prevent as much as
possible the formation of vapor, which would be sucked up by the wood and so
prevent perfect penetration of the solution. It is desirable also although not
necessary to denude the solution of air before entering the air-tight receptacle
for the same reason, viz. to prevent air entering the pores of the wood after they
have been exhausted.
The solution should be submitted to the wood so as to cover it as quickly as
possible in order to avoid the wood taking up the vapor formed, which naturally
would not contain the ingredients.
The solution having been run in as described, pressure is usually applied so
as to assist the impregnation. When the wood is sufficiently saturated the solu-
tion is drawn off and the wood dried. It may be that continuous boiling of the
wood in the solution for a prolonged period would cause eventual impregnation,
but this would be at the cost of the color, strength and durability of the wood.
The preliminary process leads to the same result without these drawbacks.
For the purpose of impregnation, solutions of any known fireproofing salts
may be used, such for example as phosphate and sulphate of ammonia dissolved
in water and rendered neutral if necessary.
Or the wood may be submitted after impregnation, to a solution of a substance
which will harden the surface and prevent absorption of moisture. Sulphate of
iron or sulphate of copper may be employed for this purpose, or a salt of zinc or a
salt of alumina, or both combined. The copper and iron salts have the drawback
that they are liable to discolor the wood and under certain conditions attack
metals. I find however that a salt of zinc, say sulphate, or a salt of alum, such
as the sulphate, or a combination of the zinc and alum salts, effects the hardening
result without the disadvantages above named, and the zinc salt has the further
advantage of preventing the corroding tendency of the sulphate of ammonia
when this is used in the fireproofing solution; this tendency being obviated I
believe by the combination of the sulphate of ammonia (more particularly) with
the sulphate of the zinc referred to when used in conjunction. The zinc and alum
salts are also excellent fireproofing ingredients; consequently they do not affect
the fireproofing qualities of the wood.
As an example of the hardening solution the following is given, but liberty is
reserved to alter the proportions or employ either ingredient separately:-
Sulphate of iron or zinc
Sulphate of alumina
Water
3 parts by weight
1 part by weight.
Sufficient to make a 15 per
cent. solution.
In carrying out this part of the invention I find it convenient to accurately
arrange the depth of the hardening and water resisting superstratum in the wood,
and I prefer to effect this in the following manner. When the fireproofing solu-
tion has been run back from the impregnated wood in the retort or evlinder. the
wood is allowed to remain in the cylinder, and then exhaust is applied to drive
off a certain amount of moisture, more or less, according to the depth of harden-

page_text: fireproofing qualities, and any precipitate of insoluble salts that may occur in the
wood will help the water resisting qualities of the wood.
The hardening process allows of using such a salt as acetate of alumina with
phosphate of ammonia, which cannot be used in the same solution owing to the
instant decomposition which is produced on admixing these solutions. Phosphate
of ammonia being an excellent fireproofer and acetate of alumina an excellent
waterproofer, their combination is very desirable.
The method of hardening just described is preferable in the case of wood that is
not required to undergo much working after treatment, such as piles, sleepers,
rafters, joists &c., or when it has to undergo exposure, such as transit before being
worked up.
In the case of wood that will be considerably worked up afterwards it is
preferred to use ingredients as little hygroscopic as possible (such as ammonia
salts and sulphate of alumina) while still possessing preserving and fireproofing
qualities, and to cover the wood after a thorough drying with a thin waterproofing
coat say of shellac or copal. Complete drying of the impregnated wood is impor-
tant as the least heart moisture will burst through under the influence of heat
and crack the surface, and on evaporation will leave a fine crust or powder com-
posed of the ingredients used. For this reason slow and equable drying is
preferable.
In the case where the after use of the wood renders it necessary to guard
against absorption of moisture and the consequent corrosion of metals in contact
with it, such as nails, there may be incorporated with the fireproofing ingredients
some substance such as size or gelatine, which will materially assist in the object
aimed at.
Should such substances as size or gelatine be used in the fireproofing solution,
the effect of the after application of zinc or alum salts will be to harden them and
cause the wood to be practically waterproof. I am aware that it is not new
broadly speaking to employ size or gelatine in fireproofing solutions, but they
have not hitherto been used in the impregnation of wood in conjunction with
hardening materials, because the gelatine would be coagulated by those materials
before it could enter the wood. When however size or gelatine is employed,
I incorporate it in the fireproofing ingredients, in which case the after applica-
tion of the hardening materials as above described will cause the size or gelatine
to coagulate in the substance of the wood and thereby cause resistance to moisture.
It is obvious that the treatment must vary according to the description of wood
and according to the eventual use of the wood, whether for piles, sleepers, or for
carpenters' and joiners' use.
It may happen that impregnation to a certain depth only is required, in which
case the duration of treatment may of course vary, and the preliminary treatment
may not be necessary.
It is not essential, though I consider it very important, except in the case of
thin wood or of easily impregnated wood to submit the wood to the preliminary
treatment before the impregnating process, that is to say the latter process can
be followed without the preliminary treatment.
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. The process of treating wood to prepare it for impregnation with a fireproofing
or other solution, which process consists in first subjecting the wood to a vacuum
when in the condition of moist heat, and then to a medium such for example
as water feither in a liquid, vaporised or atmoised state), or methylated spirit,
which will dissolve out soluble and fermentable constituents from the pores of
the wood, the said medium or solvent being used in conjunction or not with a
saponifying medium, and pressure being preferably employed to enforce the action
of the medium or solvent, all substantially as hereinbefore described.

page_text: 2. The process of treating or preserving wood which consists in first impregnat-
ing it with a fireproofing or other solution, and then submitting it to the action
of a hardening solution, whereby the surface of the impregnated wood becomes
to any required depth water resisting or both water resisting and corrosion
resisting to metals, all substantially as herein before described.
3. The process of treating or preserving wood which consists in first impregnat-
ing it with a solution of sulphate of ammonia or of phosphate of ammonia, or of
both combined, and in then submitting it to the action of a salt of zinc, or a salt
of alumina or of both combined, substantially as and for the purposes described.
4. The method or process of treating wood to render it fire and water resisting
and to harden same, which process consists in first impregnating the wood with
a fireproofing solution in conjunction with a substance such as gelatine or size,
and in then impregnating the wood with a hardening solution, substantially as
and for the purpose described.
Dated this 7th day of September 1898.
J. C. MEWBURN & ELLIS,
55 and 56, Chancery Lane, London, Chartered Patent Agents.