Improvements in or relating to the Impregnation of Wood with Fire- proofing, Waterproofing, Preserving, or Colouring Materials.
Year: 1898

page_text: Date of Application, 25th Feb., 1898
Complete Specification Left, 22nd Nov., 1898-Accepted, 23rd Dec., 1898
Improvements in or relating to the Impregnation of Wood with Fire-
proofing, Waterproofing, Preserving, or Colouring Materials.
I, HENRY VALENTINE SIMPSON, of 2, Army and Navy Mansions, Victoria Street,
Westminster, London, Lieutenant in the Royal Navy, do hereby declare the
nature of this invention to be as follows:-
This invention relates to the impregnation or saturation of wood with materials
either for rendering it fireproof or waterproof, or for preserving or colouring it,
and has for its object to effect a perfect impregnation of the wood for a considerable
depth.
The apparatus required in order to put this invention into effect comprises
an air tight receiver, in which the wood to be treated is placed, and which should
be capable of withstanding at least 100 lbs. external or internal pressure; a boiler
connected therewith, capable of supplying steam pressure up to 60 lbs.; and an
air pump connected with the receiver, capable of maintaining a vacuum in the
cylinder of about 28 barometric inches.
Considerable difficulty has hitherto been experienced in impregnating wood to
any depth, especially in the case of hard woods.
The great obstacle to a satisfactory impregnation of wood is caused by the
nature of the volatile and soluble constituents of the wood and the closeness
of the pores, and the present invention is designed to remove these difficulties.
For the purpose of this invention the wood to be treated is enclosed in an air
tight receiver and submitted to the action of steam, the heat of which and the
time of subjection depending on the description of the wood under treatment and
the nature of that particular description.
In order that the structural strength of the wood should not be impaired the
action of the steam should not be prolonged beyond a certain time. Oak for
example if exposed too long to the action steam at a certain temperature, is
very apt to warp and crack. Soft woods such as deal, pine ash and the like are
apt to become discoloured under the same conditions, whilst teak, mahogany,
pitch pine, and the like will stand more severe steaming without material
deterioration.
When the action of the steam has been prolonged a sufficient time, the steam
is blown off and the receiver exhausted by means of an air pump. The action
of the steam is to heat the wood throughout whilst not vulcanizing it, and to
penetrate the pores getting rid of the air and volatile matter and some of the more
soluble constituents, a great proportion of which are drawn out of the receiver
with the steam and air.
The impregnating solution can then be run into the receiver and it will fill the
pores and with sufficient pressure thoroughly impregnate the wood.
The process in the case of certain woods and certain thicknesses of wood may
be advantageously repeated until the required object is obtained.
I have discovered that wood under the action of steam as above described first

page_text: begins to gain weight probably by the absorption of water that condenses from
the steam, and then at a certain period begins to lose weight as it becomes
thoroughly warm and some of the constituents are driven off. There comes a
time when the weight is approximate to and in some cases somewhat less than the
original weight of the wood when placed in the receiver and this is the proper
time to submit it to the solution.
I have also discovered that the resistance to the evolution of the volatile and
soluble constituents is partially due to their resistance to being dissolved by
ordinary steam and partially to the somewhat acid nature of the wood, and if this
resistance can be overcome a much deeper impregnation of the wood can be
obtained. Part of this invention consists in a method of overcoming this resistance.
For this purpose I proceed as follows:-
When the wood has been steamed to its proper point a vacuum is formed by the
pump. I then introduce a certain quantity of a volatile solvent such as liquor
ammonia which under the action of the vacuum is immediately drawn in and
turned into vapour. The pores of the wood being to a great extent empty this
ammonia vapour is able to permeate the wood. The effect of the ammonia is,
as I believe, partly to neutralize the acid nature of the wood and partly to soften
and render more amenable the less soluble (in water) constituents of the wood.
Allowing the gas a few minutes to effect this permeation, I then cause steam at
a high pressure to be led into the receiver. The steam and ammonia vapour
mingle and the pressure of the steam drives the ammonia gas, now diluted with
the steam, far into the pores of the wood. I maintain this pressure for as long
as it is necessary to effect the purpose. I use the steam in order to obtain the
pressure, but I may of course obtain the pressure by the use of a pump, and pump
in the ammonia gas at the required pressure. When the ammonia gas is
sufficiently driven into the pores of the wood I shut the connection between the
boiler and the receiver and allow the receiver to cool, aiding it if necessary with
cold water through internal coils or pipes, the result being that a vacuum of
about 29 inches, if the work is properly performed, can be produced, caused by the
partial condensation of steam and ammonia gas and thus the condensed gases
around the wood and its pores are able to act on the wood. I leave the wood in
this state for a little time and allow the ammonia to act upon the soluble con-
stituents and on the wood and so clear the way for the required solution of the
fireproofing or other ingredients. If the receiver is air tight a vacuum is well
maintained at not under 28 inches. Under certain conditions I may at this point run
in the solution which will be sucked up by the wood. Or I may employ the air
pump to exhaust the steam and ammonia combined with a certain proportion of
the volatile matters which may be held in suspension and may maintain a vacuum
by the pump until I consider the wood is ready for the solution. (The ammonia
drawn off can be condensed and recovered if desired). I then cause the solution
to be run in either hot or cold according to circumstances, and the nature of the
ingredients used. In certain cases for instance where the wood is of a resinous
nature, the ammonia treatment may be repeated. I may, of course, cause the
ammonia and steam to enter together, and I may use superheated steam in order to
lessen the amount of condensation while still maintaining the pressure and so not
dilute the ammonia too much. These modifications must necessarily depend more
or less on the nature and the quality of the wood to be treated. In lieu of
ammonia I may use volatile substances such as alcohol, formaldehyde, carbon
bisulphide or the like or I may use any of these combined.
A characteristic feature of this invention is the application of some substance
that will act as a solvent and not lose its property when vapourized. This differs
essentially from the use of a fireproofing solution in the form of a vapor for the
purpose of saturating the wood with the fireproofing solution in a vapourized form
as has already been proposed. When a solution, the vehicle of the ingredients
of which is water, is vapourized, the water is thrown off in the form of steam
leaving as a general rule the ingredients behind, its main object namely impregna-

page_text: tion of the wood with the desired ingredients, being thus to some extent
defeated.
The use of ammonia in the treatment above described is particularly advantageous
when the ingredients used in the subsequent impregnating solution contain
ammonia salts because the ammonia liable to be lost is I believe replaced by
the ammonia in the wood and in the receiver.
There are other advantages in the use of ammonia as proposed, viz. that it
will assist the subsequent drying of the wood. It is in itself fire-resisting, and if
some gelatinous body be used in the impregnating solution such as gelatine, gum
or the like, will have the effect of hardening it. If formaldehyde be used it has
the effect of rendering insoluble any gelatinous substance that may be employed
in the impregnating solution.
For impregnating the wood I may use any of the following novel non-
hygroscopic solutions which are comprised in my invention:-Sulphate or phos-
phate of ammonia and lime with or without ammonia in the proportions of
say 1b. of sulphate or phosphate of ammonia to 1 gallon of saturated aqueous
solution of lime and (wlien used) 1 oz. of ammonia.
Sulphate or phosphate of ammonia, zinc and lime with or without ammonia in the
proportions of say 14 oz. of sulphate or phosphate of ammonia and 2 oz. of zinc
to 1 gallon of saturated aqueous solution of lime and (when used) 4 oz. of ammonia.
Sulphate or phosphate of ammonia and zinc in the proportions of say 14 oz. of
sulphate or phosphate of ammonia to 4 oz. of zinc.
The above proportions are only approximate and can be greatly varied.
The amount of ammonia employed in the impregnating solution will be to some
extent governed by the amount of ammonia which has been used in the preliminary
treatment of the wood.
The various compounds and proportions should be regulated by the nature of
the wood and the uses to which it will subsequently be applied.
In certain cases I may replace the zinc with copper or with a combination of
zinc and copper with sufficient ammonia to dissolve it so as to form a hydroxide
of cupra-ammonia or of cupra-zinc ammonia.
I may in the above case impregnate the wood with the sulphate or phosphate
of ammonia and with the hydroxide of cupra-ammonia or of cupra-zinc ammonia
separately. If the cupra-ammonia or cupra-zinc ammonia be applied separately
and after the sulphate or phosphate, the effect is to gelatinise the external coating
of cellulose which will form when dry an external impervious coating. If the
cupra-ammonia be applied before the sulphate or phosphate it will tend to soften
the pores and to form a closer combination with the cellulose and the other
ingredients.
Instead of the sulphate or phosphate of ammonia I may use the hydroxide of
alum preferably precipitated from sodium aluminate, or a combination of sulphate
or phosphate of ammonia and hydroxide of alum or phosphate of alum.
Dated this 25th day of February 1898.
J. C. MEWBURN & ELLIS,
55 and 56, Chancery Lane, London, Chartered Patent Agents.
Improvements in or relating to the Impregnation of Wood with Fire-
proofing, Waterproofing, Preserving, or Colouring Materials.
I, HENRY VALENTINE SIMPSON, of 2, Army and Navy Mansions, Victoria Street,
Westminster, London, Lieutenant in the Royal Navy, do hereby declare the

page_text: 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:-
This invention relates to the impregnation or saturation of wood with materials
either for rendering it fireproof or waterproof, or for preserving or colouring it,
and has for its object to effect a perfect impregnation of the wood for a considerable
depth.
The apparatus required in order to put this invention into effect comprises an
air tight receiver, in which the wood to be treated is placed, and which should be cap-
able of withstanding at least 200 lbs. pressure; a boiler connected therewith, capable
of supplying steam pressure up to 60 lbs.; and an air pump connected with the
receiver, capable of maintaining a vacuum in the cylinder of about 28 barometric
inches.
Considerable difficulty has hitherto been experienced in impregnating wood to
any depth, especially in the case of hard woods.
The great obstacle to a satisfactory impregnation of wood is caused by the
nature of the volatile and soluble constituents of the wood and the closeness of
the pores, and the present invention is designed to remove these difficulties.
For the purpose of this invention the wood to be treated is enclosed in an air
tight receiver and submitted to the action of steam, the heat of which and the
time of subjection depending on the description of the wood under treatment
and the nature of that particular description.
In order that the structural strength of the wood should not be impaired the
action of the steam should not be too prolonged and the steam should not be of
too high a temperature. Oak, for example, if exposed too long to the action of
steam at a high temperature, is very apt to warp and crack. Soft woods such as
deal, pine, ash and the like are apt to become discoloured under the same con-
ditions, whilst teak, mahogany, pitch pine and the like will stand more severe
steaming without material deterioration and with beneficial increase of impregnation.
Generally speaking soft woods may be subjected to steam at a temperature below
but not above boiling point. For hard woods the temperature may be increased
to 2200 without detriment.
When the action of the steam has been prolonged a sufficient time depending on
the nature and the thickness of the wood (for pine of one inch thickness say 4
to 5 hours), the steam is blown off and the receiver exhausted by means of an air
pump. The action of the steam is to heat the wood throughout whilst not
vulcanizing it, and to penetrate the pores getting rid of the air and volatile matter
and some of the more soluble constituents, a great proportion of which are drawn
out of the receiver with the steam and air.
The impregnating solution can then be run into the receiver and it will fill the
pores and with sufficient pressure will thoroughly impregnate the wood.
The process in the case of certain woods and certain thicknesses of wood may be
advantageously repeated until the required object is obtained.
I have discovered that wood under the action of steam as above described first
begins to gain weight by the absorption of water that condenses from the steam,
and then at a certain period begins to lose weight as it becomes thoroughly warm
and some of the constituents are driven off. The necessary heat to accomplish
this may be acquired by means of steam coils or by admitting steam of high
temperature, if necessary superheated, care being taken not to discolour the wood.
There comes a time when the weight is approximate to and in some cases some-
what less than the original weight of the wood when placed in the receiver and
this is the proper time to submit it to the solution.
I have also discovered that the resistance to the evolution of the volatile and
soluble constituents is partially due to their resistance to being dissolved by
ordinary steam, and if this resistance can be overcome a much deeper impregnation
of the wood can be obtained and at the same time a preservative medium can be

page_text: introduced into the wood. Part of this invention consists in a method of over-
coming the resistance above referred to. For this purpose I proceed as follows:-
When the wood has been steamed to its proper point a vacuum is formed by
the pump. I then introduce a certain quantity of a volatile solvent such as liquor
ammonia which under the action of the vacuum is immediately drawn in and
turned into vapour. The pores of the wood being to a great extent
empty this ammonia vapour is able to permeate the wood. The
effect of the ammonia is, as I believe, to soften and render more
amenable the less soluble (in water) constituents of the wood. Allow-
ing the gas a few minutes to effect this permeation, I then cause steam at
a high pressure to be led into the receiver. The steam and ammonia vapour
mingle and the pressure of the steam drives the ammonia gas, now diluted with
the steam, far into the pores of the wood. I maintain this pressure for as long as
it is necessary to effect the purpose. I use the steami in order
to obtain the pressure, but I may of course obtain the pressure
by the use of a pump, and pump in the ammonia gas at the required
pressure; this latter method is useful when the heat of steam would be detrimental
to the wood. When the ammonia gas is sufficiently driven into the pores of the
wood I shut the connection between the boiler and the receiver and allow the
receiver to cool, aiding it if necessary with cold water through internal coils or
pipes, the result being that a vacuum of about 29 inches, if the work is properly
performed, can be produced, caused by the partial condensation of steam and
ammonia gas and thus the condensed gases around the wood and in its pores are
able to act on the wood. I leave the wood in this state for a little time and
allow the ammonia or other solvent to act upon the soluble constituent and on the
wood and so clear and cleanse the way for the required solution of the fireproofing
or other ingredients. If the receiver is air tight a vacuum is well maintained at
not under 28 inches. Under certain conditions I may at this point run in the
solution which will be sucked up by the wood. Or preferably I may employ the
air pump to exhaust the steam and ammonia combined with a certain proportion
of the volatile matters which may be held in suspension and may maintain a
vacuum by the pump until I consider the wood is ready for the solution. (The
ammonia drawn off can be condensed and recovered if desired). I then cause the
solution to be run in either hot or cold according to circumstances, and the nature
of the ingredients used. In certain cases, for instance, where the wood is of a
resinous nature, the ammonia or similar treatment may be repeated. I may, or
course, cause the ammonia or other volatile solvent and steam to enter together,
and I may use superheated steam in order to lessen the amount of condensation
while still maintaining the pressure and so not dilute the ammonia too much.
These modifications must necessarily depend more or less on the nature and the
quality of the wood to be treated. In lieu of ammonia I may use volatile and
preservative substances such as alcohol, formaldehyde, carbon bisulphide or the
like or I may use a combination of some of these.
A characteristic feature of this invention is the application of some substance
that will act as a solvent and not lose its property when vapourized. This differs
essentially from the use of a fireproofing solution in the form of a vapor for the
purpose of saturating the wood with the fireproofing solution in a vapourised form
as has already been proposed. When a solution, the vehicle of the ingredients
of which is water, is vapourized, the water is thrown off in the form of steam
leaving as a general rule the ingredients behind, its main object namely impregna-
tion of the wood with the desired ingredients, being thus to some extent defeated.
The use of ammonia in the treatment above described is advantageous when the
ingredients used in the subsequent impregnating solution contain ammonia salts
because the ammonia liable to be lost is I believe replaced by the ammonia in the
wood and in the receiver.
There are other advantages in the use of ammonia as proposed, riz.,-It is in
itself fire-resisting, and if some gelatinous body be used in the impregnating

page_text: If zinc salts are used I may omit the ammonia. When both sulphate and
phosphate of ammonia are used I recommend 10 oz. of the sulphate to 4 oz. of the
phosphate.
When the commercial salts are used and which contain a certain proportion of
free acid I find it useful to add lime water to neutralize the acid; but when the
salts are comparatively pure I may omit the alkali.
The above proportions are only approximate and can be greatly varied.
I employ zinc on account of the property I have discovered it possesses, of
reducing the corrosive tendency of ammonia salt. There are two forms in which
it may be used, viz. as salts and as a hydrate. To the best of my belief it never has
been before employed in the form of a salt in combination with phosphate of
ammonia owing to the supposed necessary formation and precipitation of zinc
phosphate. have discovered however that when employed in proportions such
as those above given the presence of the ammonia salts preserves the phosphate
of zinc if formed in solution, it is therefore applicable to my process of impregna-
tion; nor has zine hydrate been used before in combination with ammonia salts
for the purpose of rendering wood non-inflammable or of preserving it.
In certain cases where I wish to guard against undue absorption of moisture
I may replace the zinc with copper or with a combination of zinc and copper with
sufficient ammonia to dissolve it so as to form a hydroxide of cupra-ammonia or of
cupra-zinc ammonia.
In the above case when it is undesirable that decomposition should take place
I impregnate the wood with the sulphate or phosphate of ammonia and with the
hydroxide of cupra-ammonia or of cupra-zinc ammonia separately. If the cupra-
ammonia or cupra-zinc ammonia be applied separately and after the sulphate or
phosphate the effect is to gelatinise the external coating of cellulose which will
form when dry an external impervious coating. If the cupra-ammonia be applied
before the sulphate or phosphate it will tend to soften the pores and to form a
closer combination with the cellulose and the other ingredients.
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 preparing wood for impregnation with, and of impregnating
it with, fireproofing, waterproofing, preserving or colouring materials which con-
sists in submitting the wood to the action of steam, then to a vacuum, then to the
action of liquor ammonia or other volatile solvent under steam or other pressure,
then producing a vacuum or allowing a vacuum to form, and then after allowing
time for the ammonia to act, running in the impregnating solution, all these
operations being effected in the same receiver as a continuous series, substantially
as and for the purpose set forth.
2. The use in the impregnation of wood of a non-hygroscopic and anti-corrosive

page_text: solution consisting of sulphate and phosphate of ammonia and a salt of zinc with
or without ammonia and with or without lime, substantially as set forth.
3. The use in the impregnation of wood of a non-hygroscopic and anti-corrosive
solution consisting of sulphate and phosphate of ammonia, hydrate of zinc and
ammonia with or without lime, substantially as set forth.
4. The impregnation of wood with a solution of sulphate or phosphate of
ammonia or both and then with a solution of cupra-ammonia or cupra-zinc
ammonia, or first with a solution of cupra-ammonia or cupra-zine ammonia and
then with a solution of sulphate or phosphate of ammonia or both, substantially
as and for the purpose set forth.
Dated this 22nd day of November 1898.
J. C. MEWBURN & ELLIS,
55 and 56, Chancery Lane, London, Chartered Patent Agents.