IMPROVEMENTS IN PRESERVING WOOD
Year: 1873

page_text: '
LETTERS PATENT to John Clayton Mewburn, of 169, Fleet Street,
in the City of London, Patent Agent and Consulting Engineer,
for the Invention of "IMPROVEMENTS IN PRESERVING WOOD."-A com-
munication from abroad by Alexandre Hatzfeld, of Nancy,
France
PROVISIONAL SPECIFICATION left by the said John Clayton Mewburn
at the Office of the Commissioners of Patents, with his Petition,
on the 12th July 1873.
I, JOHN CLAYTON MEWBURN, of 169, Fleet Street, in the City of
London, Patent Agent and Consulting Engineer, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN PRESERVING WOOD," to
be as follows:-
There are two processes of preserving wood, which have hitherto been
generally employed for railway sleepers, telegraph posts, and other
purposes; firstly, injection of sulphate of copper made in the, open

page_text: atmosphere and by the action of the weight of a large charge of the
liquid; and, secondly, impregnation by creosote effected in closed
vessels, and under the pressure of several atmospheres or in a vacuum.
The injection of sulphate of copper gives imperfect results. This salt,
which is very soluble, becomes diluted with rain and the humidity of t
the soil, so that in time the sulphate disappears and the wood is no
longer preserved. The preservation by creosote on the other hand is
very expensive, the process is difficult and requires costly apparatus and
great care, besides, it is necessary to make frequent analyses to ascertain
that the liquid is in the proper condition to effect the preservation. 1
Every sleeper absorbs about 20 quarts of liquid, which raises the cos tof
the preparation to about 18/8d per sleeper, while the injection of sulphate
of copper costs only about 7%.
After the employment of sulphate of copper was given up the use of
metallic salts has not been persevered in, however, besides the antiseptic ]
properties which they possess in common with creosote they have the
great advantage of considerably hardening the wood, and of producing a
sort of petrefaction which prevents it becoming disorganized. But a
simple and economical mode of causing the wood to become impregnated
with an insoluble salt is requisite. Two soluble substances by their 1
combination form an insoluble salt, this, for example, is produced by
the succesive employment of gallo-tannic acid and sulphate of iron.
I treat the wood by boiling in open vessels or by other known modes.
The process consists simply in boiling the wood in an extract of gallo-
tannic acid or in injecting this acid into it, and afterwards boiling the
wood in a solution of sulphate of iron, heating the bath, and allowing it
to cool once or several times.
t
For oak, which contains a considerable quantity of gallo-tannic acid,
it is sufficient to employ the bath of sulphate of iron only. This process
which has the property of hardening the wood allows of the use of fir
and other more or less soft woods, for purposes for which they have
hitherto been considered unfit on account of their softness.
The two substances required for the preservation are easily obtained
and inexpensive, the cost of the two processes will not exceed that of
the injection of sulphate of copper.

page_text: Wood preserved by this process can be applied to other purposes
besides railway sleepers and telegraph posts, for example, in factories
and works where the deleterious action of the gases and fluids quickly
affects the hardest wood, and where wood is now generally replaced by
iron and bricks, even for floors. With this process it is unnecessary to
impregnate the wood to the heart, because being impregnated to a
certain depth the combination of the wood and salt forms a sort of metal
case, which quite preserves the heart.
The employment of gallo-tannic acid and sulphate of iron is only an
example, as other bodies will produce analogous results, the Invention
consisting in the impregnation of the wood with an insoluble salt, which
hardens it and renders it unalterable.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said John Clayton Mewburn in the Great Scal Patent
Office on the 31st December 1873.
•
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
CLAYTON MEWBURN, of 169, Fleet Street, in the City of London, Patent
Agent and Consulting Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twelfth day of July, in the year
of our Lord One thousand eight hundred and seventy-three, in the thirty-
seventh year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said John Clayton Mewburn, Her special
licence that I, the said John Clayton Mewburn, my executors, adminis-
trators, and assigns, or such others as I, the said John Clayton Mewburn,
my executors, administrators, and assigns, should at any time agree
with, and no others, from time to time and at all times thereafter,
during the term therein expressed, should and lawfully might make,
use, exercise, and vend, within the United Kingdom of Great Britain
and Ireland, the Channel Islands, and Isle of Man, an Invention for
"IMPROVEMENTS IN PRESERVING WOOD," (a communication to me from abroad
.by Alexandre Hatzfeld, of Nancy, France), upon the condition (amongst
others) that I, the said John Clayton Mewburn, my executors or adminis

page_text: >
trators, by an instrument in writing under or their, or one of their
hands and seals, should particularly describe and ascertain the nature of
the said Invention, and in what manner the same was to be performed,
and cause the same to be filed in the Great Seal Patent Office within
six calendar months next and immediately after the date of the said
Letters Patent.
NOW KNOW YE, that I, the said John Clayton Mewburn, 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 thereof, that is to say :-
There are two processes of preserving wood which have hitherto been
generally employed for railway sleepers, telegraph posts, and other
purposes; firstly, injection of sulphate of copper made in the open
atmosphere and by the action of the weight of a large charge of the
liquid; and, secondly, impregnation by creosote effected in closed vessels
and under the pressure of several atmospheres or in a vacuum.
The injection of sulphate of copper gives imperfect results. This salt,
which is very soluble, becomes diluted with rain and the humidity of
the soil, so that in time the sulphato disappears and the wood is no
longer preserved. The preservation by creosote on the other hand is
very expensive, the process is difficult and requires costly apparatus and
great care, besides it is necessary to make frequent analyses to ascertain
that the liquid is in the proper condition to effect the preservation.
Every sleeper absorbs about 20 quarts of liquid, which raises the cost of
the preparation to about 1s./8d. per sleeper, while the injection of sul-
phate of copper costs only about 7d.
After the employment of sulphate of copper was given up the use of
metallic salts has not been persevered in, however, besides the antiseptic
properties which they possess in common with creosote they have the
great advantage of considerably hardening the wood and of producing a
sort of petrefaction, which prevents it becoming disorganized. But a
simple and economical mode of causing the wood to become impregnated
with an insoluble salt is requisite. Two soluble substances by their
combination form an insoluble salt, this, for example, is produced by
the successive employment of gallo-tannic acid and sulphate of iron.
I treat the wood by boiling in open vessels or by other known modes.
The process consists simply in boiling the wood in an extract of gallo-

page_text: tannic acid or in injecting this acid into it, and afterwards boiling the
wood in a solution of sulphate of iron, heating the bath, and allowing it
to cool once or several times.
For oak, which contains a considerable quantity of gallo-tannic acid,
it is sufficient to employ the bath of sulphate of iron only. This process
which has the property of hardening the wood allows of the use of fir
and other more or less soft woods for purposes for which they have
hitherto been considered unfit on account of their softness.
The two substances required for the preservation are easily obtained
and inexpensive, the cost of the two processes will not exceed that of
the injection of sulphate of copper.
Wood preserved by this process can be applied to other purposes
besides railway sleepers and telegraph posts, for example, in factories
and works where the deleterious action of the gases and fluids quickly
affects the hardest wood, and where wood is now generally replaced, by
iron and bricks, even for floors. With this process it is unnecessary to
impregnate the wood to the heart, because being impregnated to a
certain depth the combination of the wood and salt forms a sort of metal
case, which quite preserves the heart.
The employment of gallo-tannic acid and sulphate of iron is only an
example, as other bodies will produce analogous results, the Invention
consisting in the impregnation of the wood, substantially as herein-
before described, with an insoluble salt, which hardens it and renders it
unalterable.
In witness whereof, I, the said John Clayton Mewburn, have here-
unto set my hand and seal, this Thirty-first day of December,
One thousand eight hundred and seventy-three.