IMPROVEMENTS IN THE MATERIALS POR PREVENTING THE ESCAPE OF HEAT FROM THE SURFACES OF CYLINDERS, BOLLERS, AND OTHER VESSELS OR APPARATUS CONTAINING HEAT
Year: 1869

page_text: LETTERS PATENT to James Howden, of Glasgow, in the County of
Lanark, North Britain, Engineer, for the Invention of "IMPROVEMENTS
IN THE MATERIALS POR PREVENTING THE ESCAPE OF HEAT FROM THE SURFACES
OF CYLINDERS, BOLLERS, AND OTHER VESSELS OR APPARATUS CONTAINING
HEAT."
Sealed the 10th August 1869, and dated the 3rd April 1869.
COMPLETE SPECIFICATION filed by the said James Howden at the
Office of the Commissioners of Patents, with his Petition and
Declaration, on the 3rd April 1869, pursuant to the 9th Section of
the Patent Law Amendment Act, 1852.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JAMES
HOWDEN, of Glasgow, in the County of Lanark, North Britain, Engineer,
send greeting.
WHEREAS, I am in possession of an Invention for "IMPROVEMENTS IN
THE MATERIALS FOR PREVENTING THE ESCAPE OF HEAT FROM THE SURFACES OF
CYLINDERS, BOILERS, AND OTHER VESSELS OR APPARATUS CONTAINING HEAT," and

page_text: have petitioned Her Majesty to grant unto me, my executors, adminis-
trators, and assigns, Her Royal Letters Patent, for the same, and have
made solemn Declaration that I verily believe myself to be the first and
true Inventor thereof.
NOW KNOW YE, that I, the said James Howden, do hereby declare
that the following Complete Specification, under my hand and seal,
fully describes and ascertains the nature of my said Invention, and the
manner in which the same is to be performed :-
My Invention consists in the employment of the substance known
as plaster of Paris, having the property of being run or put into moulds
or spaces in a fluid or semi-fluid state, and of rapidly solidifying
thereafter without the application of heat for enveloping the surfaces
of cylinders, boilers, pipes, or other vessels containing heat, so as to
protect them from the cooling effect of a surrounding atmosphere of
lower temperature. The protection of vessels containing heat has
hitherto been usually effected in a more or less perfect degree by
covering the surfaces of the vessels with sheets of hair felt, which are
again covered with wood, sheet iron, lead, or canvas; or instead of hair
felt non-conducting compositions mixed with hair or fibrous material are
applied in a plastic state to the surfaces in successive layers which are
dried one by one by heat maintained during the process in the vessel to
be protected until the desired thickness is attained. Hair felt as is
well known is soon destroyed by the heat from the vessels to which
it is applied, while the use of the compositions herein-before referred
to is often unsatisfactory, their application tedious and expensive and
in some cases difficult on account of the high temperature which has
to be maintained in the vessels while being covered.
The material I employ according to this Invention can be applied
to the vessels to be protected whether they are cold or hot as it
solidifies in a few minutes, and the whole process of application may
be completed in a short space of time. Besides being one of the best
non-conductors of heat known it also has the properties of durability
and adhesiveness in a high degree, and of being impervious to water;
it can thus be exposed to the atmosphere in all states of the weather.
In applying the plaster of Paris according to my Invention I surround
the vessel or surface to be protected in some cases wholly or in part
by an envelope of sheet iron, lead, wood, or other suitable material,
placing the envelope at a distance apart from the surface equal to the

page_text: thickness required for the non-conducting material. The plaster of
Paris is then made up in its liquid state and run or poured into the
space between the envelope and surface of the vessel until the space
is filled. The plaster of Paris in a few minutes solidifies without the
application of heat, and the envelope may either remain permanently
or be removed after the space is filled. When it is removed and no
other covering used the surface of the plaster which can be made very
smooth may he painted, varnished, or otherwise similarly treated, to
give it a finished appearance. It is not always necessary that an
envelope be employed for the whole of the surface to be covered,
those parts only may have an envelope on which the plaster cannot be
poured or laid against while in a semi-fluid or plastic state. Horizontal
surfaces can be easily covered to the required thickness by the fluid
in the most fluid state by having temporary edgings to prevent the
plaster from running off before it solidifies.
In covering pipes it is preferred to have a sheet iron envelope in two
halves extending from flange to flange and equal in inside diameter
to the diameter of the flanges. The plaster is run in by one or more
small holes until the space is filled, when the envelope may be removed
and the process repeated on another length of piping. If space be
required to allow of the bolts or nuts at the pipe flanges to be taken
out the envelope can be made to stop the plaster covering at the required
distance, and this space may be filled up by pieces which can be taken
off and replaced when desired.
In covering large surfaces such as boilers the plaster of Paris can
be applied part by part of such extent as may be found most convenient
until the whole is covered, as this substance unites firmly together
though applied in parts at different intervals of time. This material
as applied according to my Invention has the property of adhering
firmly to the under sides of vessels, or in any position, or to any part
of the surface. Though not necessary, it may, if desired, be covered,
after being applied with sheet iron, lead, wood, canvas, or other like
material.
My Invention also consists in mixing the plaster of Paris with a certain
quantity of gelatinous or glutinous matter before application to the
surfaces to be protected; this mixture makes the plaster more tenacious
and elastic, also prevents it setting too quickly, and permits of its being
more easily applied while in a plastic state and levelled or smoothed

page_text: on its surface by trowels, straight edges, or other similar tools. This
matter should be added in suitable proportions to obtain such results.
A certain portion of lime which should not exceed one-half the
quantity of the whole material may be mixed with the plaster of Paris
without destroying its properties, and may be used in such a case as
when a sufficient supply of the plaster of Paris cannot be obtained
during the process of application to cover the whole surface under
treatment. As the non-conducting and other desirable properties of the
plaster of Paris are slightly deteriorated by such admixture it is pre-
ferable to use the plaster or the plaster with the gelatinous or glutinous
mixture only as herein-before described.
Having now particularly described the nature of my Invention, and
the manner of performing the same, I do not confine myself to the
precise details of operating herein laid down; but what I claim is,-
Firstly. The employment of plaster of Paris, substantially in the
manner and for the purposes herein-before described.
Secondly. The mixing plaster of Paris with gelatinous or glutinous
matter, as herein-before described.
In witness whereof, I, the said James Howden, have hereto set
my hand and seal, this Second day of April, in the year of our
Lord One thousand eight hundred and sixty-nine.
JAMES HOWDEN. (L.S.)