Improvements in and relating to the Treatment of Wood, with Solu- tions for Rendering it Non-flammable and for other Purposes.
Year: 1899

page_text: Date of Application, 31st May, 1899
Complete Specification Left, 28th Feb., 1900-Accepted, 7th Apr., 1900
Improvements in and relating to the Treatment of Wood, with Solu-
tions for Rendering it Non-flammable and for other Purposes.
I, HENRY VALENTINE SIMPSON, Lieutenant R.N., of 2, Army and Navy Man-
sions, Victoria Street, Westminster, in the County of London, do hereby declare
the nature of this invention to be as follows:-
My invention relates to a method of treating wood for the purpose of making
it non-flammable, or otherwise preserving it and of introducing colouring matter
into it if desired.
Heretofore for these purposes the lumber to be treated has been enclosed in
an air-tight receptacle and then heated by direct contact with steam, or by
means of internal steam-coils or hot jackets, for a considerable time. When the
wood has been sufficiently heated, a portion of the constituents are withdrawn
therefrom and the pores are exhausted of air by a vacuum pump. Then the
chemical solution is admitted and immediately fills the empty pores. The
impregnation may be assisted by pressure.
This process has, under certain conditions, given good results, but it has been
found to possess the following disadvantages: that is to say the direct action
of heat on wood in its ordinary condition (either as dry heat or in the form of
steam), is liable to affect its structural strength, to darken its colour, and to
otherwise alter its characteristics. Moreover the heating adds considerably both
to the length of time and the cost of the treatment.
Now my invention relates parily to means whereby better impregnation can
be obtained than when live steam or hot air is used in contact with the wood
in its ordinary condition as hitherto, thus avoiding the possibility of injuring
or discolouring the wood and also effecting considerable economy of fuel.
One method of carrying this part of my invention into practice is as follows:
I employ a horizontal, cylindrical receptacle, with an opening at one or both
ends, capable of being hermetically sealed by means of doors. The cylinder
and doors must be capable of withstanding from 250 to 300 lbs. hydraulic pres-
sure per square inch. In connection with the cylinder, I may employ an air-
pump for creating an exhaust, a pressure pump for obtaining the necessary
pressure, and the usual connections with tanks holding the impregnating solu-
tion.
The wood to be treated, which can be of the ordinary trade sizes and descrip-
tions, is placed on cars which run on rails into the cylinder. The door is then
closed and the solution admitted into the cylinder until the latter is full, when
pressure is applied by the pump for the necessary time, say 20 hours, depending,
however, on the character and dimensions of the wood. The solution is then
returned to the tanks.
In the case of soft wood of slight thickness, such as matching, electric wire
casing, and veneering, the above specified time will be found sufficient to effect
saturation, and the wood can now be withdrawn, and as no steam or other heat
has been used the wood will not be affected in respect of its colour or otherwise.

page_text: In the case of harder kinds of wood or greater thicknesses of soft wood, only
a partial impregnation will have been effected and I therefore continue the
treatment as follows, riz.
When the wood is partially impregnated, as above described, the cylinder
may or may not be exhausted by means of a vacuum pump: sufficient live steam
is then led into the cylinder to cause ebullition of the solution already in the
wood. This ebullition when the vacuum pump is employed being in a vacuum,
takes place at a low temperature, and the wood is therefore not subjected to an
injurious temperature.
The effect of this ebullition of the solution in the wood is to render the wood
amenable for further impregnation.
When this ebullition has continued for, say, three or four hours, the steam
is cut off, the vacuum being maintained and the solution is again admitted to
the wood under pressure, when the wood will be found to have taken up a
considerably increased quantity of the solution.
In the case of very thick or very hard woods, this operation may be advan-
tageously repeated.
In certain cases, I may heat the wood as above described without creating a
vacuum. The ebullition will then take place at the ordinary temperature of
boiling water without ill effects, for, when the wood is partially impregnated
even this great heat does not appear to affect it. A characteristic feature of
this part of my invention is the application of heat only after the wood has
been partially impregnated with the solution without heat.
My invention also relates to the solutions for treating wood according to my
invention.
There are two well known methods or processes of impregnation. One of
these is known as the double solution method and consists in impregnating the
wood by successive solutions which cause double decomposition on meeting, thus
precipitating in the wood insoluble matter which cannot be washed out. The
disadvantage of this process is the length of time required, the extensive appa-
ratus, and the considerable precipitation formed on the outside of the wood,
causing waste and an unsightly appearance, and also injury to any tools that
may be used in working the wood thereafter.
The other, or the single solution method, consists in using fire-proof ingre-
dients which are soluble in water, the wood being impregnated with the solution
and the water being driven off by evaporation, leaving the salts in the wood.
The disadvantage of the single solution method is, that the solution employed
being necessarily soluble in water is liable to be washed out on exposure to
the weather, or if the wood is subjected to washing or scrubbing: the wood is
also liable to absorb moisture so that it will corrode metals and will be in other
respects inconvenient.
Now, a characteristic feature of this part of my invention, is a novel method
whereby a desirable proportion of insoluble matter can be introduced into the
wood in a single solution, thus affording practically all the advantages of both
the double and single solution methods without any of the disadvantages apper-
taining thereto.
In order to obtain this desirable result, I make use of the property possessed
by combination of certain salts which, although soluble in water, at a certain
strength will, on the strength of the solution being increased by the evaporation
of the water, crystallise out as insoluble precipitate. As an example, I may
mention the combinations of phosphate of ammonia, sulphate of ammonia, and
sulphate of zine in solution with water in certain proportions, say 6, 6 and 2,
at a certain strength of solution, say 16%. The wood is impregnated, as above
referred to, with this solution, which is soluble at that strength, then the water
is driven off by evaporation, either in the open air or in kilns, and so the
solution in the wood gets stronger causing eventually a considerable quantity
of the insoluble precipitate of phosphate of zine to form throughout the wood,

page_text: and so sealing the ammonia salts in the pores of the wood. If the solution is
used cold and no heat used in the drying, the sulphate of ammonia may be
omitted.
Another example is a solution of phosphate of ammonia, sulphate of ammonia
and sulphate of magnesia in the proportion of 6, 6 and 1 in this case the
result may be assisted by the formation of phosphate of magnesium, which would
take place if any ammonia be set free in the dry-rooms or kilns. Still another
example is a combination of sulphate of ammonia, sulphate of zinc and boracic
acid in the proportion of 10. 3 and 2, the boracic acid forming
borate of zine which is crystallised in the wood on the strength of
the solution being increased by evaporation. I find the proportion of insoluble
matter thus formed is, in the above specified proportions, sufficient to effect my
purpose of rendering wood water-resisting or non-absorbent, non-flammable
and non-corrosive. The proportions may under circumstances depending on the
nature of the wood and the method of impregnation be somewhat varied.
When colouring matter is to be introduced into the wood, it may be added
to the solution used for rendering the wood non-flammable, or if the wood is
to be coloured only and not rendered non-flammable a coloured solution of any
known constituents may be used instead of the nonflammable solution.
Dated this 21st dov of Vov 1800
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.
Improvements in and relating to the Treatment of Wood with Solu-
tions for Rendering it Non-flammable and for other Purposes.
I. HENRY VALENTINE SIMPSON, Lieutenant R.N., of 2, Army and Navy Man-
sions, Victoria Street, Westminster, in the County of London, 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:-
My invention relates to a method of treating wood for the purpose of making
it non-flammable, or otherwise preserving it and of introducing colouring matter
into it if desired.
According to the method hitherto generally adopted for these purposes, the
lumber to be treated is enclosed in an air-tight receptacle and then heated by
direct contact with steam, or by means of internal steam-coils or hot jackets, for
a considerable time. When the wood has been sufficiently heated, the con-
stituents are partially withdrawn therefrom and the pores are exhausted of air by
a vacuum pump. Then the chemical solution is admitted and immediately fills
the empty pores, the impregnation being sometimes assisted by pressure.
This process has, under certain conditions, given good results, but it has been
found to possess the following disadvantages: that is to say,the direct action of
heat (either as dry heat or steam) on wood in the ordinary condition of the latter
is liable to affect its structural strength, to darken its colour, and to otherwise
alter its characteristics. Moreover the heating adds considerably to the length
of time and to the cost of the treatment.
Now my invention relates to the treatment of wood with solutions of the kind
hereinafter specified or with other suitable solutions, in such manner that better
impregnation can be obtained than when live steam or hot air is used in contact

page_text: with the wood in its ordinary. condition as hitherto, so that the possibility of
injuring or discolouring the wood will be avoided, and considerable economy of
fuel will be effected. Moreover when using the said solutions I am able to intro-
duce into the wood insoluble matter so as to seal the fireproofing salts in the
pores of the wood.
For treating the wood according to my invention I employ a horizontal, cylin
drical receptacle having at one or both ends, an aperture capable of being closed
and hermetically sealed by a suitable door. The cylinder and doors must be
capable of withstanding from 250 to 300 lbs. hydraulic pressure per square inch.
In connection with the cylinder, I employ an air-pump for creating an exhaust, a
pressure pump for obtaining the necessary pressure, and the usual connections
with tanks holding the impregnating solution.
The wood to be treated can be of the ordinary trade sizes and descriptions.
If very wet, it is preferably first dried to some extent, and is placed on cars
or trucks which run on rails into the cylinder. The door is then closed and the
solution admitted into the cylinder until the latter is full. Pressure is then
applied by the pump for the necessary time, (say 20 hours), which depends on
the character and dimensions of the wood. The solution is then returned to the
tanks.
In the case of soft wood of slight thickness, such as match-boarding, electric
wire casing, and veneering, the above specified time will be found sufficient to
effect saturation. The wood can then be withdrawn, and as no steam or other heat
has been used the wood will not be affected in respect of its colour or otherwise.
In the case of the harder kinds of wood or greater thicknesses of soft wood, only
a partial impregnation will have been effected by the above operation and I
therefore continue the treatment as follows: riz.:-
When the wood is partially impregnated, as above described, the cylinder may
or may not be exhausted by means of a vacuum pump. Sufficient live sicam is
then admitted into the cylinder to cause ebullition of the solution already in the
wood. When the vacuum pump is employed, this ebullition takes place at a
low temperature, and the wood is therefore not subjected to an injurious
temperature.
The effect of this ebullition of the solution in the wood is to prepare the wood
for further impregnation.
When this ebullition has continued for, say three or four hours, the steam is
cut off, (the vacuum being maintained), and the solution is again admitted to
the wood under pressure, when the wood will be found to take up a considerably
increased quantity of the solution.
In the case of very thick or very hard woods, this further treatment may be
advantageously repeated.
In certain cases, I may heat the wood as above described without creating a
vacuum. The ebullition will then take place at the ordinary temperature of
boiling water without ill effects, for, when the wood has been previously partially
impregnated even this great heat does not appear to injuriously affect it."
There are two well known methods or processes of impregnation. One of these
is known as the double solution method and consists in impregnating the wood
by successive solutions which cause a reaction on meeting, thereby fireproofing
the wood and precipitating in the wood insoluble matter which cannot be washed
out.
The disadvantage of this process is the length of time required, the extensive
apparatus, and the considerable precipitation formed on the outside of the wood,
causing waste and an unsightly appearance, and also injury to any tools that
may be used in subsequently working the wood.
The other, or the single solution method, consists in using fire-proof ingredients
which are soluble in water, the wood being impregnated with the solution and
the water being driven off by evaporation, leaving the salts in the wood.
disadvantage of the single solution method is, that the ingredients employed,
The

page_text: being necessarily soluble in water, are liable to be washed out on exposure to
the weather, or by washing or scrubbing the wood which moreover is liable to
absorb moisture so that it will corrode metals and will be in other respects incon-
venient.
Now, the ingredients of the solution I employ and their proportions are such
that I can introduce, as already stated, a desirable proportion of insoluble matter
into the wood in a single solution, thus affording practically all the advantages of
both the double and single solution methods without any of the disadvantages
appertaining thereto.
In order to obtain this desirable result, I make use of the property possessed
by the combination of certain salts which, although soluble in water at a certain
strength, will, on the increase of strength of the solution by the evaporation of
the water or other volatile matter, crystallise out as insoluble precipitate. As
an example, I may mention the combination of phosphate of ammonia, sulphate
of ammonia, and sulphate of zine in certain proportions, say 6, 6 and 2, in solu-
tion with water at a certain strength of solution say 16 per cent. The wood is
impregnated, as above set forth, with this solution, then the water of the solu-
tion is driven off from the wood by evaporation, either in the open air or in kilus,
and so the solution in the wood increases in strength causing eventually the for-
mation of a considerable quantity of an insoluble precipitate of probably phos-
phate of zinc or some compound salt throughout the saturated part of the wood,
and sealing the ammonia salts in the pores of the wood. If the solution is used
cold and no heat is used in drying off the water of the solution, the sulphate of
ammonia may be omitted.
According to another example I use a solution of phosphate of ammonia, sul-
phate of ammonia, and sulphate of magnesia in the proportion of
6, 6 and 1: in this case the result may be assisted by the formation of
phosphate of magnesium, which would take place if any ammonia be set free
in the dry-rooms or kilns. Still another example is a combination of sulphate
cf ammonia, sulphate of zinc or of magnesia and boracic acid in the proportion of
10, 3 and 2, the boracic acid forming borate of zinc or of magnesia which is
crystallised in the wood on the increase of strength of the solution by evaporation.
In order to prevent too great acidity of this last mentioned solution I may add
thereto a small proportion of potash or other suitable alkali.
I find the proportion of insoluble matter thus formed is, in the above specified
proportions, sufficient to effect my purpose of rendering wood water-resisting or
non-absorbent, non-flammable and non-corrosive. The proportion may, under
circumstances depending on the nature of the wood and the method of impregna-
tion, be somewhat varied.
When colouring matter is to be introduced into the wood, it may be added to
the solution used for rendering the wood non-flammable; or if the wood is to be
coloured only and not rendered non-flammable a coloured solution of any known
constituents may be used instead of the non-flammable solution.
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 treatment of wood by a method or process in which the wood is impreg
nated or partially impregnated with non-flammable matter without the prior
application of heat to the wood, substantially as and for the purposes specified.
2. The treatment of wood for rendering it non-flammable and for other pur-
poses by a method or process consisting in partially impregnating the wood with
a solution, then subjecting it to the action of steam either with or without a
vacuum, and then further impregnating the wood with the same solution, sub-
stantially as described for the purposes specified.
3. A solution for the impregnation of wood, composed of a mixture of salts
which are soluble in water at a certain strength of solution but which are pre-

page_text: cipitated and also react to produce an insoluble salt when the strength of the
solution is increased by evaporation, substantially as and for the purposes specified.
4. The treatment of wood with a solution of phosphate of ammonia, sulphate
of ammonia and sulphate of zine, in the proportions of 6, 6 and 2; or with a
solution of phosphate of ammonia, sulphate of ammonia and sulphate of magnesia
in the proportions of 6, 6 and 1; or with a solution of sulphate of ammonia,
sulphate of zine or of magnesia and boracic acid in the proportions of 10, 3 and 2,
substantially as and for the purposes specified.
Dated this 28th day of February 1900.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.