Improvements in or relating to the Treatment of Porous Materials.
Year: 1897

page_text: PROVISIONAL SPECIFICATION.
Improvements in or relating to the Treatment of Porous Materials.
I, HUBERT HIGGINS, of 4, Trinity Street, Cambridge, in the County of Cam-
bridge, Demonstrator of Anatomy to Cambridge University, do hereby declare
the nature of this invention to be as follows:
66
This invention has a very wide application and relates to the treatment of
porous materials, such for example as stone, wood, bricks or burnt clay, though
I do not limit the application of the invention to these materials only. By
the use of this invention I am able to alter the qualities of the material treated
or even to convert them into, physically speaking, substantially different
materials. The invention will be understood from the following description.
I will describe it first as applied to wood. I take the wood preferably in
the green or a wet condition, and subject it in any suitable apparatus to the
action of steam, preferably superheated, and at or about atmospheric pressure.
The effect of this appears to be to expel the contents of the interstices and
replace them by the superheated steam. I now apply in any convenient manner
a solution of the material with which I desire to impregnate the wood, and this
causing condensation of the steam in the pores of the wood forms a partial
vacuum, and causes the fluid to be introduced into the pores. After this the
solution is removed and the steam may be again applied, with the effect of driv-
ing off the moisture or vehicle, which has carried in solution the materials to
be deposited in situ. The material deposited may if necessary be converted into
an insoluble material by subsequent treatment, or more of the original material
can be introduced in a similar manner.
If desired pressure in excess of the atmospheric pressure may be employed at
any portion of the process, whether the pressure be obtained by steam pressure
pneumatic, or otherwise.
The same or similar treatment may be applied in the case for example of
stone, the material to be precipitated being selected according to the require-
ments of the case. For example if it be desired to render wood capable of
resisting the action of fire, a suitable silicate, may be used, for instance it is
obvious that a soluble silicate such as the silicates of potassium or sodium can
be first introduced, and converted into an insoluble silicate in situ by the subse-
quent introduction of other soluble salts such as calcium chloride or magnesium
chloride, but I do not bind myself to the use of any particular ingredients.
From this it will be appreciated that a particular feature of the invention
comprises the substitution for moisture or the other materials already in the
wood or other material to be treated of other materials. The material to be
introduced may be in either a liquid, vaporous or gaseous form, and may be
introduced at or subjected to pressures above atmospheric pressure, and any
number of applications may be made.
Although I prefer to employ, as above stated, superheated steam at atmo-
spheric pressure as the heating agent, I wish it to be understood that I do not

page_text: bind myself to the use only of steam, the important feature being to suitably
apply the heat throughout the material to be treated, and that the material
should be contained in an atmosphere of saturated steam or superheated steam.
It will be obvious that provided the application of heat is of sufficient in-
tensity, and the application sufficiently prolonged, that even the interior of a
block of considerable thickness can be heated to the desired extent, but it may
be desirable or necessary to treat the surface only of a given block of material.
Dated this 3rd day of December 1897.
BOULT & WADE,
Agents for the Applicant.
Improvements in or relating to the Treatment of Porous Materials.
I, HUBERT HIGGINS, of 4, Trinity Street, Cambridge, in the County of Cam-
bridge, Demonstrator of Anatomy to the Cambridge University, 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; -
This invention deals essentially with adaptation and modifications for the
purpose of treating porous materials, of the processes described in the Specifica-
tions of the Patents granted to me Nos. 28886 of 1896 and 7664, 7665, 7667
and 7668, all of 1897. The processes as employed in these forms of apparatus
enable me to subject porous substances to the action of superheated steam. I
can by this means partially or completely desiccate such porous substances as
yarus, textile, fabrics wood, stone and the like. I can also by pouring liquid
on such substances facilitate their impregnation by the condensation of the
superheated steam in their interstices and the creation of a partial vacuum.
I attain great economy by using in this process alternate superheaters regula-
table or not regulatable and chambers, as set forth in Patent No.. 7664/97
already referred to, and finally heating air for desiccating purposes, to such an
extent as to cause condensation of the steam, which may in the first instance
be exhaust steam when such is available.
The device of employing alternate superheaters (regulatable or not) and cham-
bers can also be adapted to the apparatus set forth in Patents Nos. 7665, 7667
and 7668 before referred to.
In carrying out the invention the material to be treated is surrounded by or
exposed to a current of superheated steam in any convenient chamber or recep-
tacle. This has the effect of desiccating the porous body to any desired ex-
tent; the superheated steam surrounding it may then be replaced by the sub-
stance in liquid form with which it is desired to treat the said body, sufficient
of the former being introduced to completely cover it. This produces a partial
vacuum by condensing the superheated steam contained in the interstices of
the material thus considerably aiding in its impregnation.
-
I find it advisable to cause the steam to rise evenly from the lower part of
the chamber. I carry this out by introducing the steam at the bottom of the
chamber, preferably through perforated pipes arranged on the floor beneath a
perforated metallic partition, which thus forms a false floor to the chamber.
The period of time that I cause the material to be subjected to the action of
the steam and the temperature at which I employ it, are modified by the qualities
of the different materials I treat.
In the process of partial or complete desiccation of wood, by using such
temperatures as are suitable to the dimensions, degree of desiccation and charac-

page_text: ter of the wood I treat, I find that by subjecting wood to the action of super-
heated steam preferably at atmospheric pressure for a certain period, I produce
coagulation of the coagulable ingredients of the wood, which prevents the short
shavings and diminished properties of resistance to strain characteristic in wood
rapidly dried in air (i.e. in 7-14 days).
It is necessary, when it is desired to preserve harden or colour wood by the
formation of those combustion products having antiseptic and preservative
properties, to first dry the wood thoroughly at a temperature, of about 150-170° C
and afterwards to continue the action of the steam till the combustion products
are formed and the wood is suitably coloured.
To prevent cracking of the wood I find it necessary to cool the wood slowly
and if practicable under pressure.
When I desire to impregnate wood I provide pipes leading into the chamber
through which I can introduce the fluid with which I desire to impregnate the
wood, which may be placed in convenient receptacles in the chamber, while it
is under the action of superheated steam.
I find that as would be expected only crystalloids are easily introduced into
wood, colloids tend to block up the peripheral openings of the interstices. Most
useful salts for treating wood are the soluble silicates of sodium and potassium,
which are either not introduced at all, or with great difficulty, on account of
certain acid substances in the wood combining with the sodium or potassium
to liberate silicic acid which blocks up the pores and forms a half-permeable
membrane. I obviate this undesirable occurrence by mixing with the silicate
an alkali such as the hydrates of sodium or potassium, or sodium or potassium
carbonate, or I may first saturate the wood with an alkali. In this way I find
that it is much more easy to introduce a second salt such as calcium, aluminium,
or magnesium chloride, to produce the precipitation of an insoluble silicate
throughout the whole structure of the wood.
Having now particularly described and ascertained the nature of this
invention and in what manner the same is to be performed, I declare that what
I claim is:
-
1. The process above described for treating porous materials.
2. Producing coagulation of the coagulable ingredients of wood by the action
of superheated steam applied and operating substantially as described.
3. In the above described process combining an alkali with sodium or potas-
sium silicate to prevent the precipitation of silicic acid.
4. In apparatus for the treatment of porous bodies with superheated steam
admitting the steam to the chamber through a perforated false bottom substan-
tially as described.
Dated this 3rd day of September 1898.
BOULT & WADE,
Agents for the Applicant.