Improvements in Enamelled Leather and in Enamel for Producing the same.
Year: 1899

page_text: Date of Application, 27th June, 1899-Accepted, 5th Aug.,
1899
COMPLETE SPECIFICATION.
Improvements in Enamelled Leather and in Enamel for Producing
the same.
I, GEORGE SIGFRIED WOLFF, of 927, North Front Street, in the City of Phila-
lelphia, State of Pennsylvania, United States of America, Leather Manufacturer,
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:
My invention consists in the manufacture of enamelled leather having the
coating of enamel applied directly to the grain surface of the leather and it also
comprises an enamelling compound prepared for application in this way.
The figure in the accompanying drawing represents an exaggerated section of a
piece of leather having an enamel coating applied directly to the grain surface
thereof in accordance with my invention.
6
patent" leather has been to
The usual method of preparing enamelled or
apply the enamel to what is termed a "buffed grain," that is to say, the natural
grain surface has been removed by means of an instrument called a "buffing
knife" or "slicker" in order to secure a roughened foundation upon which to
apply the enamel and insure the adherence of the same to the leather, the natural
grain of the leather presenting a smooth surface, to which enamel coatings,
prepared in the ordinary manner, will not properly adhere.
66
Ordinary enamel or patent" leather coatings consist of linseed, or other
drying, oils, boiled to a pasty, or gummy, consistency so that it can be spread
in thin layers which will not be absorbed by the leather, and which, when dried,
form a foundation upon which to apply as many coats of thin varnish as is
requisite in order to obtain the desired finish.
Besides failing to adhere properly to the smooth grain surface of the leather,
an oil, boiled to the usual pasty consistency, would be more, or less, opaque and
hence would hide the grain of the leather if applied directly thereto, while,
if of less than a pasty consistency, it would, to a greater, or lesser, extent, be
absorbed by the leather.
In carrying out my invention, therefore, I discard the usual foundation applied
to a "buffed" surface of the leather and apply directly to the smooth grain
surface a varnish which has been rendered elastic, adherent, and non-absorbable
by the grain surface, this result being attained by the addition to the oil used as
a foundation for the varnish, of a medium which will impart the desired qualities
to the said oil without thickening it to such an extent that it will hide the grain
surface of the leather.
The medium which I prefer to use is gum chicle, and I combine with this
india rubber and camphor, or their equivalents.
The varnish, or enamel, at some period during the treatment, possesses such
fluidity as will insure its taking hold of the grain surface of the leather and
adhering firmly thereto, and the said varnish is preferably so fluid in the first
instance that it can be applied by means of a brush, or sponge, although it may,

page_text: without departing from my invention, be of such a consistency that it may have
to be applied by means of a dabber, spatula, or like implement, and heating or
other treatment be subsequently resorted to to give it the desired fluidity.
I take the leather of whatever kind selected, after it has been prepared up to the
point where it would, in the ordinary course of, treatment, be finished as either
glazed, ironed, or dull surface leather. This leather is then dampened, stretched,
dried, "soft-boarded" and again dried and stretched as is common in the ordinary
practice of making "patent" leather, or enamelled" leather, and I then apply
directly to the grain surface of the stretched skin a coating of the varnish herein-
after referred to as "
Varnish No. 1," the coated skin being then dried, or baked,
in a suitable oven at a temperature of about 180° Fahrenheit, and then exposed
to the air, until the coating of varnish has become thoroughly dry and hard.
I then apply a second coating of the varnish hereinafter referred to as "Varnish
No. 2" and dry, or bake, this second coating in the same manner as the first,
after which the leather is again exposed to the air for the purpose of removing
the slight stickiness inherent to a freshly varnished surface, whereupon the
leather is removed from the stretching frame, and is ready for the market.
In preparing the oil for Varnish No. 1, I first heat the oil to a temperature of
about 400° Fahrenheit, using, by preference, ordinary linseed oil, into which,
when heated to the temperature named, I introduce from one half to one per cent.
of Prussian blue, or other oxidizing agent, the temperature being then raised to
about 520° Fahrenheit and kept at that point for from two and a half hours, to
three and a half hours, or more, depending upon the character of the oil employed,
after which the oil is allowed to cool until it reaches a temperature of 125°
Fahrenheit whereupon I introduce into it fifty per cent. of benzine, this addition
being for the purpose of rendering the boiled oil sufficiently fluid to permit of its
effective application by means of a brush, or sponge, the benzine evaporating
immediately after such application, so as to leave the oil upon the surface in the
same condition as though it had been applied alone, if such application had been
possible.
In preparing the oil for Varnish No. 2 I also prefer to use ordinary linseed oil,
which I heat to a temperature of about 400° Fahrenheit, and then introduce into
it eight per cent, of an oxidizing agent, such as Prussian blue if the varnish be
intended for black leather, or ten per cent. of an oxidizing agent such as borate of
manganese, if intended for colours other than black. The temperature is then
raised to about 520° Fabrenheit and continued at that point for about one-and-a-
half hours after which the oil is allowed to cool until it reaches a temperature of
about 125° Fahrenheit whereupon I introduce into it fifty per cent. of benzine
for the same purpose as that hereinbefore set forth, the effect of the greater
amount of oxidizing agent employed in this compound as compared with Varnish
No. 1, being to cause it to dry more quickly and to present a surface which, when
dry, will not be, or become, sticky.
I also prepare solutions of chicle, rubber and camphor in the following
manner:-
A given weight of chicle is masticated in an equal volume of turpentine until
the whole has been reduced to a syrupy mass which is then strained through a
cloth so as to produce a clear liquid.
India rubber is also masticated in turpentine, using, however, four volumes of
turpentine to one volume of rubber employed, the mixture being kept at a
temperature of about 180° Fahrenheit for three days by any suitable means, such
for example as a water bath, and the product is then strained through a cloth.
Gum camphor is dissolved in twice its own weight of turpentine and. also
strained through a cloth.
In preparing Varnish No. 1, I take of the linseed oil prepared for that purpose
in the manner before stated, one-hundred and fifteen parts, and of the camphor
solution forty-five parts, and mix the two by stirring them, together,, whereby
they immediately combine. I next stir into the compound twenty parts of the

page_text: chicle solution, and, when this has been effected, I add twenty parts of the india
rubber solution, and I then run the whole compound through a paint mill, or other
mixing apparatus, previously introducing a pigment of any desired character, as
such is needed, which will, by the action of the mill, be intimately mixed with,
and ground into, the varnish.
After being subjected to the action of the paint mill the varnish is strained
through cloths and is then ready for use.
For Varnish No. 2 I take of the oil prepared for the purpose in the manner
hereinbefore set forth, seventy parts, and of the camphor solution thirty parts,
and, after mixing the two, I strain the mixture through a cloth, and then thin it
with sufficient benzine to cause it to flow freely.
The main purpose of the chicle and camphor in the compound is to render
the varnish non-absorbable by the leather but as the chicle gum if used alone
would render the coating brittle and the camphor alone would render the coating
less lustrous, I use both, and add the rubber for the purpose of giving the varnish
the desired toughness and elasticity.
My invention is not limited to the use of the three gums in the manner
described, the essential feature of this part of my invention being that the
medium, or media, employed in addition to the base, or menstruum, shall be such
as to impart to the varnish those properties which render it elastic, adherent and
non-absorbable, whereby it can be applied directly to the grain surface of the
leather.
The enamel coating produced in accordance with my invention does not
hide the grain surface of the leather.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim is:-
1. As a new article of manufacture, flexible enamelled leather having directly
upon its unbuffed grain surface an adherent enamel coating.
2. An enamel coating for leather consisting of a base, or menstruum, such as
boiled oil, combined with a medium whereby it is rendered elastic, adherent,
and non-absorbable.
Dated this 27th day of June 1900.
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C.
Agents.