Improvements in the Manufacture of Enameled Metallic Ware.
Year: 1896

page_text: Date of Application, 29th Sept., 1896-Accepted, 7th Nov., 1896
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Enameled Metallic Ware.
I, ALEXANDER NIEDRINGHAUS, of No. 304, North Eighth Street, in the City of
St. Louis, State of Missouri, United States of America, Gentleman, 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 relates to a new and useful improvement in the manufacture
of enameled ware, and consists essentially in the method of treating the base, or
that part which is to be enameled.
Heretofore, in the manufacture of enameled ware, iron has generally been used
as a base. Steel has been used to a greater or less extent for some wares, but with
the result, generally, that pin holes, flecks, and chips, occur to such an extent as to
constitute a serious objection to its use, destroying the beauty and impairing the-
usefulness of the enameled ware. Pin holes, as they are called, appear irregularly.
over the enameled surface, and are the result of the development of a gas or gases
beneath the enamel coating, during the fusion of the glaze, forming bubbles, which,
bursting, expose the black metal beneath. Flecks, as they are called, also appear
irregularly over the enameled surface, but are apparently produced by different or
modified causes from that ascribed to pin holes. These flecks, or scale-like chips,.
differ in depth and size. Some of them extend down to, and expose the surface of
the base, while others are more shallow, and show the dark color of the glaze near the
base. In many instances, the enamel is not entirely flecked off, but is loosely
attached, appearing white where the rupture of the fleck extends beneath the
surface of the enamel. Moreover, it is known that these fleckings occur after the
ware has been removed from the muffle, and it may be some time before they
appear. Chips, or chippings, as they are called, are generally found at corners of
the ware and expose the surface of the base to a considerable extent. This is
supposed to be the result of insufficient attachment of the enamel to the base,
aggravated by the strain of gases in some cases, causing it to flake or chip off in large
pieces and expose the base.
I am aware that colored enamel, consisting of two or more coats, has been applied.
to steel. This is accomplished by burning the first coat, which is usually colored
with cobalt or manganese, into the steel under excessive heat. If any of the defects-
to which I have heretofore referred, are present in this first coat they are cured
or covered by the second coat of soft and easy fusing glaze which is generally
opaque so as to hide the first coat.
I will now describe my invention, and, in the beginning, desire to be understood.
as not limiting myself to the exact ingredients herein named, the proportion of such
ingredients, as I have found by experiment, desirable to use, nor the particular
manner herein described of using the ingredients, as it is obvious that there are many
equivalents which could be employed with more or less success.
To begin with, in the manufacture of mottled enameled ware having steel for its.
base, the same general steps are employed to convert the raw material into a finished
article, with such exceptions as I will note, as are employed in making mottled
enameled ware with iron for its base.
The base, either steel or iron, having been rolled into sheets, is stamped or seamed
into form, and enameled.
This invention is based upon the discovery that salt petre introduced into the
annealing pot, will vaporize at a low temperature, and generate gases, which..

page_text: attacking the surface of the metal, will cleanse it, at the same time slightly etching
said surface, rendering the metal sensitive to a superior glaze of enamel."
Salt petre may be used alone in the annealing pot in about the proportions
hereinafter stated, or it may be used in conjunction with chloride of calcium, or
some other cloride or salt, with satisfactory results. Instead of chloride of calcium,
other chlorides, a salt of ammonia, or analogous salt, may be used with the salt petre,
and good results produced. Hence, this invention, which, broadly considered,
consists in placing salt petre in the annealing pot, by itself, or with other ingredients
named, so that a gas or gases will be generated in the annealing pot in the presence
of which the metal base will be annealed, will not be avoided by so changing the
ingredients or the proportions thereof, that their equivalents will accomplish the
same result.
In practicing this present invention, the salt petre is placed in the annealing pot
with the metal to be annealed, preferably in about the proportion of two pounds of salt
petre to one hundred pounds of steel, and the pot then exposed to the ordinary
annealing heat for about three to six hours. I prefer to so treat the steel in what
is known as the first annealing, that is, before the metal is shaped into vessels
by stamping or otherwise, but instead of practicing my invention in this first
annealing, it may be used with equal success after the metal has been shaped, after
which the metal ware thus treated can be enameled with beneficial results, wherein
the pin holes will not be present and the flecking or chipping will be reduced. It
will be further found that the enamel will have a close adhesion to the metal base,
which thereby makes a superior article of enameled ware.
If chloride of calcium, or any of the other ingredients named, are used in
conjunction with the salt petre in the annealing pot, I have found that about three-
quarters of a pound of such ingredients in addition to the two pounds of salt petre to
one hundred pounds of metal, will produce satisfactory results.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
.claim is:
1. The herein described process of preparing steel for enameling, which consists in
placing the steel and salt petre in the annealing pot and subjecting the same to the
ordinary annealing heat; substantially as described.
2. The herein described process of preparing steel for enameling, which consists in
placing the steel, a chloride, and salt petre in the annealing pot and subjecting the
same to the ordinary annealing heat; substantially as described.
3. The herein described process of making enameled ware, which consists in
placing the metal base in an annealing pot, placing salt petre in said pot with the
base, applying the annealing heat, and then applying the enamel to the base and
fusing the same thereon; substantially as described.
4. The herein described process of making enameled ware, which consists in
placing the metal base in an annealing pot, placing a chloride and salt petre in said po
with the base in about the proportions set forth, applying the annealing heat, and
then enameling the base; substantially as described.
Dated the 29th day of September 1896.
PHILIP M. JUSTICE,
London, Chartered Patent Agent,
For the Applicant.