Improvements relating to the Bearings of Machinery and other Surfaces liable to be Overheated, and in Paints to be Applied to such Surfaces.
Year: 1886

page_text: Date of Application, 22nd Apr., 1886.
Complete Left, 22nd Jan., 1887.
Complete Accepted, 19th Apr., 1887.
Improvements relating to the Bearings of Machinery and other
Surfaces liable to be Overheated, and in Paints to be Applied
to such Surfaces.
I, HENRY CROOKES of No. 4 Westminster Chambers Victoria Street. London
Electrical Engineer do hereby declare the nature of this invention to be as follows:-
The object of the invention is more especially to provide a means for shewing
clearly when the bearings or other parts of machinery are becoming heated. To
effect this I coat the exterior of the bearing or other part with a paint, which changes
from one color or tint to another as the surface becomes hot and which returns to its
original color as the surface cools. Preferably I employ in the composition of the
paint the double iodide of mercury and copper.
This preparation is of a bright red color at the ordinary temperature but when
heated to about 160° Fahrenheit it changes to a dark brown or black-on cooling it
resumes its original red color. As it will slowly decompose on continued heating
when exposed to air it is desirable to cover it with a hard varnish-the varnish will
also serve to protect it from rubbing and wear.
CARPMAEL & Co.,
Agents for the Applicant.

page_text: Improvements relating to the Bearings of Machinery and other
Surfaces liable to be Overheated, and in Paints to be Applied
to such Surfaces.
I, HENRY CROOKES of No. 4 Westminster Chambers, Victoria Street, London,
Electrical Engineer, 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 :-
The object of the invention is to provide a means for showing clearly when the
bearings or other parts of machinery or other surfaces are becoming heated. To effect
this I coat the exterior of the bearing or other surface with a paint which changes
from one color or tint to another as the surfaces becomes hot, and which, returns to its
original color as the surface cools. Preferably I employ in the composition of the
paint the double iodide of mercury and copper, preferably also for the sake of cheap-
ness I use this substance mixed with red lead, white lead or other pigment so.as to make
the paint of any desired tint.
The double iodide may advantageously be used with red lead in the proportion of
1lb of the double iodide to 1lb of red lead.
The double iodide may be made in the ordinary manner as described in text books'
on chemistry and which is as follows:-
Iodide of potassium is dissolved in water, a solution of mercuric bi-chloride (H, Cl₂)
is. then added so long as the precipitate at first formed, is redissolved; this solution is
then boiled and while boiling a boiling solution of sulphate of copper is added; dense
vapour of iodide immediately comes off and the solution must be kept boiling until
these fumes have entirely disappeared, the whole is then filtered, and after washing
thoroughly, the precipitate, which is the double iodide required, is dried and ground
to a fine powder, and is then ready for mixing with oil and terebene, as paint.
At any ordinary temperature (below 105° F) the paint is of a bright red color, but
when gently heated it becomes darker until at about 140° F. the colour is a dark
brown, the first change being noticeable at about 110° F. on cooling, the paint resumes
its original red color; and will therefore serve to indicate a rise of temperature any
number of times.
This property of changing color when heated, enables me to apply the paint in many
ways as a heat indicator.
For example if the bearings of any machine are painted with it, the man in charge
can tell at a glance whether the bearings are running hot or cold, for if the paint
remains red, it is a sure sign that the bearings are below 120° F. (tingling heat). If
applied to hot water pipes it is equally useful in showing when they get overheated.
For painting the handles of flat irons, saucepans, kettles, tea urns, and such like it
will be found a great convenience.
The best method of applying this paint is to first coat the bearing or other surface
with ordinary red paint of exactly the same tint as the heat indicating paint and

page_text: afterwards when this coat of paint is dry to put a few stripes or other marks of tho
heat indicating paint over it, and then varnish over all, by adopting this plan, there
will always be an unchanging standard of comparison so that the very first change of
color will be easily noticed.
Another important application is that of painting coils of wire through which an
electric current is to pass. By this means a very simple ampère meter can be made,
for if in an installation of electric lighting a certain maximum current is to pass
through any given wire say 50 ampères I place in that circuit a.coil of. wire of such
diameter that it will bear 50 ampères passing continually through it without
reaching 140° F., but sufficiently small that a slight increase of say two or three
ampères will almost immediately cause the paint to become brown, thus indicating
that the maxiinum safe current has been exceeded. Coils of dynamos can bo
protected in a similar manner.
By varying the proportion of sulphate of copper used in the manufacture, the
temperature at which the change of color begins to take place can be varied between
certain limits, viz: from about 110° F. to about 165° F.
Ordinarily I employ about 8 oz. of sulphate of copper to 17 oz. of the iodide of
mercury. This gives a yield of about 10 oz. of the double. iodide which commences
to change color at about 110° Fahrenheit. If instead of using 8 oz. of sulphate of
copper 4 oz. are used a yield of about 7 oz. of the double iodide will be obtained which
commences to change color at about 165° Fahr. If a still smaller quantity of sulphato
of copper be used a double iodide which will commence to change color at a lower
temperature will again be obtained but the yield will be small.
The paint must not be applied direct to iron, brass, copper, zinc and some other
metals but a coat of ordinary paint or varnish must be first laid on, otherwise the
paint is partially decomposed and loses its property of changing color.
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. For indicating the heating of the bearings of machinery or other surfaces which
are liable to become overheated, the coating of such surfaces with a paint. which as it
becomes heated changes from one color or tint to another and which returns to its
original color as it cools.
2. For indicating the heating of the bearings of machinery or other surfaces which
are liable to become overheated, the first coating such surfaces with the heat indicating
paint and afterwards with varnish substantially as described.
3. For indicating the heating of the bearings of machinery or other surfaces which
are liable to becoine overheated, the first coating such surfaces with ordinary red paint
then in stripes or other marks with the heat indicating paint of the same color and
afterwards with varnish substantially as described.
4. A paint for use as a temperature indicator, the coloring matter in which paint is
partly or wholly composed of the double iodide of mercury and copper.
Dated this 22nd day of January 1887
CARPMAEL & Co.,
Agents for the Applicant.