JAPANNING OR ENAMELLING METALS.
In japanning metals, all good work of which should be stoved, they
have to be first thoroughly cleaned, and then the japan ground applied
with a badger or camel-hair brush or other means, very carefully and
evenly. Metals usually require from three to five coats, and between
each application must be dried in an oven heated from 250° to 300°
F.--about 270° being the average. It has already been seen that the
best grounds for japanning are formed of shellac varnish, the
necessary pigments for colouring being added thereto, being mixed with
the shellac varnish after they have been ground into a high degree of
smoothness and fineness in spirits of turpentine. In japanning it is
best to have the oven at rather a lower temperature, increasing the
heat after the work has been placed in the oven. When a sufficient
number of coats have been laid on--which will usually be two only--the
work must be polished by means of a piece of cloth or felt dipped in
tripoli or finely powdered pumice-stone. For white grounds fine putty
powder or whiting must be employed, a final coat being afterwards
given, and the work stoved again. The last coat of all is one of
varnish. And here, as a preliminary remark, it is advisable that all
enamels and japans should be purchased ready-made, as any attempt to
make such is almost sure to end in disaster, while, owing to the fact
that such are only required for small jobs; it would involve too much
trouble and would not pay. It is for this reason that few japan
recipes are given, as, although many are available, they do not always
turn out as suitable for the purpose as could be desired, in addition
to which the ready-made articles can be purchased at a very reasonable
price and are much better prepared. The operator should procure his
enamels a shade or two lighter than he desires to see in the finished
article, allowing the chemical action due to the stoving to tone the
colours down. Another necessity is to keep the enamel thoroughly well
mixed by well stirring it every time it is used, as if this is not
done the actual colouring matter is apt to sink to the bottom, the
ultimate result being that streaky work is produced in consequence of
this indifferent mixing of the enamelling materials.
It is hardly necessary to state that all japanning or enamelling work
must be done in a room or shop absolutely free from dust or dirt, and
as far away as possible from any window or other opening leading to
the open air, for two reasons--one being that the draught therefrom
may cool the oven or stove, and the other that the air may convey
particles of dust into the enamelling shop. In fact, it cannot be too
much impressed upon the workmen that one of the primary secrets of
successful enamelling is absolute cleanliness; consequently all
precautions must be taken to ensure that the enamel is perfectly free
from grit and dust, and it must be so kept by frequent straining
through fine muslin, flannel, or similar material. The work having
been thoroughly cleaned and freed from all grease and other foreign
matter, it must be suspended or held immediately over the pan
elsewhere referred to, and the enamel poured on with an ordinary iron
ladle, or covered by means of the brush. When it has been permitted to
drain thoroughly, the work should be hung on the hooks on the rods in
the oven as seen in the explanatory sketch, care being observed that
no portion of the work is in such a position that any superfluous
enamel cannot easily drain off--in other words, the work must lie or
hang that it is always, as it were, on the slant. Always bear in mind
when shutting the oven door to do so gently, as if a slam is indulged
in all the gas jets will be blown out, and an explosion would probably
result.
Should the job in hand be a large one, it will be found as well to get
a cheaper enamel for the first coat, but if the work is only a small
job, it will not be necessary to have more than one enamel, of which a
couple of coats at least will be required. When the first coat has
thoroughly dried and hardened, the surface will have to be thoroughly
rubbed till it is perfectly smooth with tripoli powder and fine
pumice-stone, and afterwards hand-polished with rotten-stone and putty
powder. And here it may be remarked that the finer the surface is got
up with emery powder and other polishing agents the better will be the
enamelling and ultimate finish. The rubbing down being finished,
another coat of enamel must be applied and the work baked as before,
care being always taken to keep the enamel in a sufficiently fluid
condition as to enable it to flow and run off the work freely. It can
easily be thinned with a little paraffin. A third coat will frequently
be advisable, as it improves the finish.
In enamelling cycles, it is well to hang the front forks crown
uppermost when they are undergoing the final baking, and it is
advisable to bear in mind that wheels require an enamel that will
stove at a lower temperature than is called for for other parts of the
machine. Some japanners advocate the fluid being put on with camel-or
badger-hair brushes, and for the best descriptions of work, final
coats, and such like, I agree with them; but this is a detail which
can be left to the operator's own fancy, the class of work, etc.; but
I would remind him that applying enamel with a brush requires much
care and a certain amount of "knack". It is something like successful
lacquering in brasswork--it looks very simple, but is not. Each
succeeding coat of japan gives a more uniform and glossy surface, and
for this reason it may, in some cases, be necessary to repeat the
operation no fewer than half a dozen times, the final coat being
generally a layer of clear varnish only, to add to the lustre.
Care must be taken for light-coloured japans or enamels not to have
the temperature sufficiently high to scorch, or the surface will be
discoloured, as they require a lower temperature for fixing than the
dark japans, which, provided the article is not likely to be injured
by the heat, are usually dried at a somewhat high temperature. The
preceding instructions apply only to the best descriptions of work.
When pouring enamel by means of the ladle over pieces of work, do not
agitate the liquid too much--at the same time taking care to keep it
well mixed--so as to form air bubbles, as this will cause trouble, and
in pouring over the work do it with an easy and gentle and not too
hurried a motion. In japanning curved pieces, such as mud-guards,
etc., in hanging up the work in the oven see that the liquid does not
run to extremities and there form ugly blots or blotches of enamel.
When white or other light tones are used for japanning they are mixed
with japanners' varnish, and these require more careful heating in the
oven or stove than darker tints or brown or black.
[Illustration: FIG. 1.--Trough for Dipping Bedstead Frames and other
Large Work.]
ENAMELLING BEDSTEAD FRAMES AND SIMILAR LARGE PIECES.
At Fig. 1 is shown a trough in which large pieces, such as bedsteads,
bicycle frames, etc., are dipped or immersed. For the first-mentioned
class of work such high finish is not required as for bicycles, and
consequently the enamel need not be applied with a brush, nor will it
be necessary to rub down the work between each coat, but instead the
pieces can be literally dipped in the tank of liquid, then allowed to
drain on to the dripping-board--the superfluous enamel thus finding
its way back into the trough or tank, the dripped articles being
afterwards placed in the oven to harden. The trough must be of
sufficient dimensions to allow the pieces of work to be completely
immersed, and the dripping-board should be set at an angle of about
45°.
Bedstead frames will never require more than two coats and the
commoner class of goods only one. I would not advise the tradesman in
a small way of business to go to the expense of a trough, etc., as it
calls for much more room than is ordinarily available, but if he has
the necessary plant for bicycle work he can, of course, do an
occasional job of the other kind.
JAPANNING TIN, SUCH AS TEA-TRAYS AND SIMILAR GOODS.
For japanning sheet-iron articles, which are really tin goods, such as
tea-trays and similar things, first scour them well with a piece of
sandstone, which will effectually remove all the scales and make the
surface quite smooth. Then give the metal a coating of vegetable
black, which must be mixed with super black japan varnish, thinned
with turps, and well strained. Only a small quantity of this varnish
is necessary, as it will dry dead. The article must then be placed in
the stove to harden at a temperature of 212° F., there to remain for
from ten to twelve hours. When taken out of the stove, the articles
must be allowed to get cold, after which they must be given a coat of
super black japan, which, if necessary, must be thinned with turps, a
stiff, short bristle brush being employed, and the varnish put on
sparingly, so that it will not "run" when it gets warm. Two coats of
this varnish on top of the vegetable black coating are usually
sufficient, when done properly, but a third coating much improves the
work, and from ten to twelve hours' hardening will be necessary
between each coating. The small lumps which will be more or less
certain to arise will require to be rubbed down between each
application by a small and smooth piece of pumice-stone.
If it is desired to add gold or bronze bands or any kind of floral or
other kind of fancy decorations, these are painted on, after the
ground japanning has been done, in japanners' gold size, and then the
gold leaf is applied, or the bronze or other metal powder is dusted
on, after which the objects so treated are again placed in the stove,
where they will not require to be kept near so long as for ordinary
japanning. After they have been removed, the gilt or bronzed portions
must be treated with a protecting coat of white spirit varnish.
Transfers can be applied in the same way.
Tinned iron goods are the most largely japanned, and for these brown
and black colours are principally employed. Both are obtained by the
use of brown japan, the metal having a preliminary coating of black
paint when black is required. Only one coating of brown japan is given
to cheap goods, but for better articles two or more are applied. For
these it is possible that a final dressing with pumice-stone, then
with rotten-stone, and rubbed with a piece of felt or cloth, or even
the palm of the hand, may be necessary, but as a rule not.
Large numbers of articles of the above description, such as tea-trays,
tea-canisters, cash-boxes, coal-boxes, and similar goods, are japanned
at Birmingham, and it is to such that the preceding instructions
apply.
ENAMELLING OLD WORK.
In all cases of re-enamelling old work, it is absolutely necessary to
remove all traces of the first enamelling, and if this has been well
done in the first instance, it will prove no mean job. The best way to
clean the work is to soak it in a strong "lye" of hot potash, when the
softened enamel can be wiped or brushed off--this latter method being
pursued in the more intricate and ungetatable portions of the work.
New work, which has not been enamelled, can be treated in the same way
for the removal of all grease, stains, finger-marks, etc., and too
much attention cannot be paid to the initial preparation of the
surface of the metal, to have it thoroughly even and smooth, as it
adds so much to the ultimate finish and appearance of the work. Plenty
of labour must be bestowed before the final coat, as any blemish will
show through this finishing, and so mar what would otherwise be a
highly satisfactory bit of work. In all kinds of bicycle work, whether
new or old, the most satisfactory results are obtained by the
application of at least two, and sometimes four or five, successive
coats of good but thin enamel, as this will impart the necessary
perfect coat, combined with durability, a high finish, and a good
colour. A good enamel should be sufficiently hard, so as not to be
scratched on the merest touch or rubbing. It will, of course, be
understood that no solder-work must be put into the stove, or the
pieces will separate. Should any of this work be discovered, the
pieces must be taken apart, and then brazed together before being
enamelled, and put in the stove.