REQUIREMENTS OF DIFFERENT TRADES.
The following are a few of the special requirements of different
trades as to paint dipping. The details might be lengthened almost
indefinitely.
BEDSTEADS.
The methods adopted for the class of work will, of course, depend upon
the quality of the finish required. Cheap bedsteads may be done by
dipping in one coat of black japan and stoving at 350° F. In better
class work several coats may be applied either by dipping or spraying,
and each may be rubbed down after stoving. If a good enamel is used
this is unnecessary.
When the work is white several coats--say, at least three--are
necessary, for white japans cannot be made which will cover
sufficiently in one coat. White lead should not be used in this class
of work for the reason that a good deal of handling of parts is
necessary, while the rubbing down is sometimes done with glass paper
and cause dust, both of which may give rise to lead poisoning. All of
the best white japans or enamels are made on a base of zinc oxide or
lithopone (zinc sulphide), or a mixture of them.
COLLAPSIBLE GATES.
This work is usually done by dipping in paint which dries "flat,"
i.e., without gloss. The colour is, as a rule, black. In fitting and
adjusting the work in order that the parts will collapse readily it
is necessary to apply a lubricating oil where the rods meet. This
lubricating oil is difficult to remove after the adjustment has been
completed, and therefore the last coat of paint is usually put on by
hand. It is suggested, however, that raw linseed oil might be used
instead of lubricating oil, and that this could be wiped off as soon
as possible after the adjustment. In such a case the paint could be
applied by dipping, as if even a little of the raw linseed oil were
not removed it would not interfere with the drying of the paint to any
material extent.
DIPPING SEWING MACHINE PARTS.
The process employed by a very large firm of American manufacturers is
as follows:--
When the castings come from the machine shop they are boiled for 20
minutes in ammonia water to kill the grease (1 of strong ammonia to 20
of water), and are then rinsed in hot water. Any holes or inequalities
in the castings are then stopped with a filler made from dry white
lead, mixed into a stiff paste with some varnish, brown japan dryers
and dry lampblack made quite stiff. When the stopping is hard the
castings are dipped into a black metallic coating thinned with 62%
benzine to a specific gravity 850. They are then dipped with two coats
of finishing japan (sp. gr. 830) flatted with powdered pumice after
each coat and leathered off. The parts which are not plated or flatted
are given 5 hours stoving at 325° F., and are then rubbed with pumice
and carpet pad until flat. Cut out gold transfers are then fixed with
transfer varnish and the work is stoved at 185° F. The parts are then
sponged and dusted, and are given a good coat of polishing varnish (sp.
gr. 950) Finally the work is rubbed down fine with glass paper and
pumice powder and then polished with machine oil and rottenstone powder
for the iron, or rottenstone and benzine for the tables. The latter, as
well as the covers for these, are not usually dipped but brush finished.
IRON RODS.
[Illustration: Fig. 20.--IMMERSING MANGLE FRAMES.]
In most cases, iron and steel rods are best painted by immersion, as
the small surface presented would cause too much waste if spraying
were attempted. As in most cases of dipping, success depends largely
upon the means adopted for handling and dipping a number of rods at
one time. Frequently, stoving is required to harden the japan, because
a rod is often subjected to considerable wear. Perhaps the best plan
to adopt, where the number of rods to be treated warrants the outlay,
is to provide mechanism by which the rods are dipped and are at
once automatically carried into a stove, and by means of slowly
travelling chains, carried out at the other end.
An excellent contrivance for the purpose is in use at the Ford Motor
Works, at Manchester. This consists of a vertical oven, heated by gas,
and having slowly-moving endless chains running from bottom to top and
down again to a point where the rods are discharged on to inclined
runners. These rods are passed through a bath of japan, are then taken
up by the chain, and, during their progress, are baked. A gear is
provided by which the time between the entry of a rod to its discharge
may be varied from twenty to ninety minutes, or any period between,
according to the purpose for which the rod is to be used and the degree
of hardness of the japan required.
IRON WINDOW FRAMES OR CASEMENTS.
A long narrow tank, say, from 1 foot 6 inches to 2 feet wide and 15
feet long, is suitable for this class of work, which is usually done in
one coat only, and this is quite sufficient to protect the iron until
the casement is fixed in position, when it will, of course, receive
additional coats by means of a brush in the ordinary way.
It is important that the iron be dipped just as soon as it leaves the
finishing shop, and it is necessary that the surface be thoroughly
cleaned before the paint is applied, and particularly after all scale
is removed. Sometimes the application of the sand blast is necessary
for this work, but, as a rule, a vigorous application of suitable wire
brushes will suffice.
Another very important provision is a system of overhanging rails on
which the sashes or other articles can be run direct from the finishing
shop to the paint tank, and thence to any part of the building, from
which they may be taken as required for shipment.
The paint used for casements is usually grey, being as a rule made of
zinc oxide and lampblack. These pigments, when mixed with a suitable
vehicle, are very durable, while, the colour being neutral, it is
suitable as an undercoat for green, as well as nearly any other colour
which it may be desired to use as a finish. The weight of the paint
should be 13 lbs. to the gallon, and it should dry with a semi-gloss.
The elevating apparatus need only be of a simple character, and several
casements can be suspended and dipped at one time. For this purpose
a "hanger" is used, having perforations through which one end of the
hooks pass. One form is shown in Fig. 21. By the side of the tank
should be a large metal lined floor, say, 20 feet by 15 feet, or even
larger, inclined toward the tank. The frames having been plunged into
the paint, are at once withdrawn and hung in rows to dry over this
floor. The superfluous paint drips on to it and runs back through a
screen or sieve into the tank. The latter should be provided with a
cover, to be closed in when the work is not being proceeded with.
[Illustration: Fig. 21.--IRON HANGER FOR SUSPENDING SEVERAL ARTICLES TO
BE DIPPED TOGETHER.]
In this class of work it is unnecessary to employ a stirring apparatus
provided that the paint is of the right consistency, and an occasional
stirring up with a pole after the work has been suspended, say, for
example, from Saturday to Monday, will usually be all that is required.
As a matter of fact, the lowering and raising of the casements into the
paint effectually stirs it up.
METAL FURNITURE.
[Illustration: Fig. 22.--THE AUTOMATIC FINISHING OF PIANOS. CARRIER
FILLED WITH SIX COMPLETE PIANOS.]
Under this head it is intended to include such articles as deed boxes,
lockers, files and other metal goods which are required to be painted
both inside and out. An enamel stoving or baking paint is usually
employed for the purpose, while the tank must be of sufficient size to
accommodate the various articles that are to go into it. Taking a deed
box by way of example, a large iron hook, such as is shown in Fig. 32
is placed inside the box so that it is suspended at an angle; the box
or boxes are then lowered into the tank and immediately withdrawn after
all the superfluous paint runs away, care being taken that the box
hangs at a proper angle to permit of this being done. Great care must
be taken in this room to exclude all dust, which would considerably
mar the work. For this purpose wire netting of the finest mesh should
be placed over the windows so as to screen off any dust which might
otherwise enter. A system of overhead rails are made, consisting
of an L-iron on the top side of which run two rollers to which are
attached hanging gears, and is sufficient for the purpose. At
least ten minutes should be allowed for these articles to drip over
the inclined floor adjacent to the tank, and for safety's sake it is
as well to employ a workman with a brush in his hand to go over each
piece and remove any tears or runs which may possibly occur. Metal
work of the description named is then placed in a stove and baked for
three hours at a temperature of 400° F. The paint is frequently green,
which is found to be a good serviceable colour and which is attractive
in appearance. After the baking the paint is quite hard, and will
withstand more or less rough usage. If any ornamental work is required,
this is done afterwards, as explained under the head of "Stencilling."
The paint employed weighs 13 lbs. to the gallon, and a fine mesh
paint strainer must be provided, through which the superfluous paint
passes as it drips from the articles on their way to the tank. In
this case, as in others, no special stirring apparatus is required,
as the comparatively heavy vehicle and the relatively light specific
gravity of the pigment employed gives little or no opportunity for any
"settling out."
MOTOR PARTS (METAL).
The various parts which go to make up a complete motor car are
differently treated according to their shape and size. In most cases,
stoving is resorted to, because the enamel or japan is thereby
much increased in durability by the hardening which takes place in
consequence of the high temperature.
The steel rims of wheels are dipped by hand into a black japan made
especially for the purpose. They are hung on hooks and allowed to drain
for some minutes, and are then transferred to the stove, where they
are subjected to a heat of 320° F. Such parts as ribs, front and rear
wings, running boards, shields, etc., are dealt with in the same way.
Previous to dipping, these parts undergo the process known as
"pickling," by which scale, grease, etc., is removed so that a
perfectly clean surface is presented to receive the japan.
Troughs to catch the drips must be provided, and it is essential that
these be kept quite clean, so that the superfluous japan may run
through gauze and be pumped back again into the tank to be used again.
AUTOMATIC FINISHING OF PIANOS.
THE STANDARD HYDRAULIC IMMERSION SYSTEM.
Any doubt as to the perfection of finish which may be produced by a
carefully thought out system of immersion or dipping must be removed by
the fact that such a system has been in successful use for some years
for the finish of pianos. It need hardly be pointed out that such a
finish must necessarily be so well done as to approach perfection.
One firm has made a special study of this subject, viz., the Standard
Varnish Co., of London and New York, and their efforts have been most
successful.
By this method an absolutely even distribution of varnish is always
secured; no part of the piano case is neglected and an enormous
reduction in the cost of varnishing is effected. The factory output can
be readily increased as desired, as the varnish working force of the
factory can do as much or as little work as trade conditions may demand.
The mechanical details have been so perfected that every kind of
instrument can be handled satisfactorily.
The excellence of the finishing done in accordance with this system
is attributable to a large extent to its mechanical construction.
The apparatus used in connection with the Standard method of piano
finishing consists, in the first place, of a steel tank for the varnish
with an adjustable cover which can be locked when the apparatus is
not in operation, a hydraulic lift for raising the work slowly out
of the varnish, a small horse-power pump which is operated either by
steam pressure or compressed air, and in extreme emergencies where the
pressure is not adequate for heavy work, a small motor for operating
the pump.
There is also installed an apparatus similar to the automatic sprinkler
system. A fusible link or another mechanical device makes it possible
to draw off the varnish into a tank outside the main buildings at will,
and for protection in case a fire should take place in any other part
of the building.
The principal investment for the piano manufacturer is the carriers or
racks for holding the separate pieces. The cases are held firmly in the
carriers by means of springs which are adjusted for the introductory
carrier, or secured by screws in the permanent carrier which is
designed for keeping the cases in the carrier until they are ready for
rubbing. This latter method saves the labour of handling.
[Illustration: Fig. 23.--AUTOMATIC FINISHING OF PIANOS. INTRODUCTORY
CARRIER READY FOR PARTS TO BE VARNISHED.]
Carriers filled with work to be varnished are raised from the floor,
swung directly over the tank, and lowered into the varnish by means of
an hydraulic lift. The speed with which the work is raised from the
varnish is controlled by a lever conveniently located for the operator.
Once the speed has been determined and the lever set the apparatus
requires merely the supervision of an operator, who may devote
considerable time to helping his assistants reload another carrier
while the one in the tank is emerging. Generally only a limited number
of carriers are required.
When the work is to be removed between coats a large percentage can be
handled without tack in a short time after it is taken from the varnish.
In the introductory carrier, parts like piano tops, which are finished
on all sides, require a little additional care because of the
difficulty of handling. This contingency is provided for by the use of
special head pieces.
In emergencies, for rushing out an extra quantity of work, carriers
holding falls, frames and small parts may be immersed in one-half the
interval usually required.
For example, these carriers can be withdrawn in from fifteen to twenty
minutes, whereas for carriers including sides from twenty-five to
thirty minutes are required. The carriers are equipped with head pieces
adjustable to meet all peculiar local factory requirements. In fact,
these carriers can be constructed by the manufacturer to meet all his
demands.
The number of carriers necessary depends entirely upon the volume of
work to be handled. But it is desirable, when possible, to have a
sufficient number of carriers to hold all the work until the varnish is
sufficiently dry for rubbing. In this way a tremendous amount of labour
and time is saved.
Permanent carriers, in which the work has been secured by ordinary
screws, have been constructed by some manufacturers at an unusually low
cost by their own machinists in their own factories.
The work in the carriers can be easily dusted by means of air-bellows
or a compressed air-blower. Work finished in this manner is so clean
that the usual sanding is not necessary and a considerable amount of
labour thereby saved.
That the Standard hydraulic immersion system of automatic finishing
of pianos has distinct advantages over the ordinary hand process is
obvious even to the casual observer. Among the numerous advantages
which have been effected the following seem to be worthy of special
consideration:
It constitutes practically the factory's entire varnishing force.
Its use insures an even coat, free from imperfections.
Coating both sides of the work preserves the cases considerably from
shrinking and warping. A great deal of labour is saved by varnishing
both sides at once.
It requires very little more varnish than the old, slow, hand method
as there is no waste from brushes and pots and absolutely no dripping
outside the tank.
The elasticity of the Standard system of piano varnishing eliminates
the necessity of additions and reductions to the working force.
The cleanness and evenness of the finish virtually makes every coat a
flowing coat. The amount of time and effort saved in the rubbing and
polishing is tremendous, and the finish obtained is much finer, due to
the absence of uneven coating and the blemishes of pinholing and dust.
Carriers containing six complete pianos each, at an average interval of
one half-hour, will enable the factory to turn out 108 pianos with one
coating during a nine-hour working day.
Carriers containing eight complete pianos would handle 144 pianos a
day. A lift sufficiently strong to accomplish any demand placed upon
it can be installed to immerse as many carriers at once as will be
necessary.
A smaller carrier containing four pianos can be installed for the
manufacturer with a small output of pianos, which by the very nature of
its construction is handled more readily than the larger carrier.
In coating both sides of the work a decided protection against
shrinking and warping has been provided. In fact many manufacturers
are taking this precaution by brushing both sides of the work. By the
Standard method the work is automatically coated on both sides at the
same time.
Very little more varnish (not more than 5%) is required by the Standard
system than by the hand method. The inventors' own experiments, as
well as the daily use of the system by manufacturers, shows that more
varnish is wasted about the varnishing room than is required by the
immersion system to coat the unfinished side of the work. With this
method, all of the small amount of varnish that drips off falls back
into the tank.
[Illustration: Fig. 24.--LOWERING PIANO CASES INTO THE VARNISH TANK.]
[Illustration: Fig. 25.--PIANO CASES NEARLY IMMERSED.]
[Illustration: Fig. 26.--PIANO CASES WHOLLY IMMERSED.]
One of the most difficult tasks of the finishing room foreman is to
be certain that the proper reduction is made for the first and other
undercoats. This is entirely eliminated with the use of the Standard
system of piano finishing. This process alone makes it possible to
apply a minimum quantity of varnish sufficient to withstand the strain
of rubbing and polishing. This lessens the possibility of shrinking and
cracking which excessive varnish coats applied by brush involves. The
slower the speed of the lift, the less varnish is applied to the work,
consequently there is a gradual regulation of the amount of varnish for
the separate coats.
[Illustration: Fig. 27.--PIANO CASES ABOUT TO BE DIPPED.]
The foregoing description, together with the accompanying
illustrations, will enable the reader to understand the general method
adopted. It should be added that it is applicable to many other
articles besides piano cases.
The system described was invented and is controlled by the Standard
Varnish Company of London and New York.
WHEELS.
An extremely ingenious but effective machine for coating hickory wheels
with paint or japan is in use at the works of the Ford Motor Company,
Trafford Park, Manchester. It consists of a stationary cylindrical
vessel of exactly the right size to receive a wheel, which, being
placed in position, is at once lowered into a tank containing the
japan. Here it is made to revolve very rapidly, by which means the
japan is thoroughly distributed over every part. Hickory, being a hard
and comparatively non-absorbent wood, the japan might give too thick
a coating if dipped and left to dry in the ordinary way. To prevent
this, the wheel, while still revolving very rapidly, is mechanically
lifted out of the japan, and is held just above it, where it continues
to spin. This has the effect of throwing off the superfluous japan by
centrifugal force. The cylindrical sides of the apparatus catch the
japan, and it runs down into the tank below. The wheels are then taken
out by a man, who wears gloves, are stacked on edge in rows to dry,
and, after an hour or so, they receive a second coat. After twenty-four
hours, or less, they are ready for use.
The advantage of rapidly revolving the wheels is that anything in the
nature of a drip is entirely eliminated. This machine can deal with 300
wheels an hour, so rapid is the process. At the present time the Ford
Works are using 2,000 wheels a week.
SOME TYPICAL PLANTS.
In gathering information of up-to-date character to include in this
book the author has visited various parts of the country, and through
the courtesy of the firms mentioned below has examined the plants used
successfully for the treatment of many different goods. The following
is a brief description of some of the plants inspected, although it by
no means exhausts the list:--
CARRIAGE DEPARTMENT, WOOLWICH ARSENAL.
[Illustration: Fig. 28.--DIPPING A COACH BODY AT WOOLWICH ARSENAL.]
[Illustration: Fig. 29.--GENERAL VIEW OF PAINT DIPPING ROOM AT WOOLWICH
ARSENAL.]
The plant for painting wagons, etc., has been in use for about 12 years
and has been eminently successful, it being found by experience that
a paint applied by dipping proves equally durable to that formerly
applied by means of brushes. Indeed, the durability is increased for
the reason, which has been pointed out elsewhere, that the paint finds
it way into open joints and crevices which could not be reached by
a brush. In some cases a wagon is dipped bodily, while in others it is
dismantled and the different parts are dipped separately; again, the
smaller portions are placed in an open wire basket which is plunged
into the paint. The building in which this painting is done is of
considerable extent and a large paint tank is located at each end. A
wagon on being completed, or in the case of an old wagon, after having
been prepared, is brought to the first tank and is raised from the
ground and lowered into the paint, where it remains for about half a
minute. It is then immediately raised, allowed to drain over a tank for
a few minutes, and then over an inclined floor for a further period.
At the end of about half an hour a workman inspects the wagon or
other article and removes any tears or runs which may have occurred.
The paint being specially prepared this is not usually an arduous
undertaking.
The illustrations show very clearly a coach body in process of dipping.
Overhead rails run throughout the length of the building and upon these
are suspended the painted wagons, which are gradually moved along
with a very little exertion, such rails being slightly inclined to
facilitate this. By the time the series of wagons reach the further end
of the building they are ready to receive a second coat of paint, by
being dipped in the second tank. This being done they are then moved
back, being at once suspended on the rails until quite dry, when they
are hoisted to the upper part of the building, where they are left
suspended until they are required for use. The paint is, of course,
a special one which is supplied in paste form having the necessary
binding ingredients. The colour used is khaki, which is very durable,
being composed of earth colours. The thinning is done on the premises
and white spirit is employed for the purpose, not turpentine, which
would be far too expensive. Formerly benzine was employed, but this
necessitated the use of a fan to take away the fumes which came from
the spirit. Such a fan is not now found to be necessary.
The tanks are fitted with iron covers bearing upon thick felt and are
operated by means of levers placed at a distance, so that should a fire
occur they can be closed at a moment's notice. The hoist is worked
from the ground by electricity. Formerly the operator of the hoist was
located in a cab near the roof, but it was felt that this would be a
dangerous position in case of fire, and he now, as stated, does the
work from the ground. The work done at Woolwich gives an excellent
example of the actual saving which may be effected by using the paint
dipping process. Before the painting plant was put in no fewer than 200
painters were constantly employed; now about 40 are fully able to turn
out the same or even a larger number of wagons in a given time.
JAMES GIBBONS.
Most of the metal sheets as well as finished metal work of various
kinds made at these extensive works at Wolverhampton are finished by
dipping into special enamels or japans made by Messrs. Mander Bros. The
dipping is done by hand and the pieces are placed at the side of the
tank to drain. In some cases it is found necessary to go over the work
slightly with a brush to remove tears, but such work takes only a few
minutes and is used mostly as a precautionary measure.
One coat is usually found sufficient, and at the proper time the iron
sheet or metal article is stoved at 250° F. to 300° F. for two hours.
Many other articles are also dipped successfully.
HARRISON, MCGREGOR & CO.
In the extensive factories of this firm at Leigh, Lancashire, dipping
by immersion has been successfully carried on for some years past.
Various agricultural implements are dipped bodily in a tank of paint
which is fitted with a worm agitator, and is of simple construction.
The iron parts are dipped separately, being supported on suitable
hangers, while the very small parts are placed in wire baskets for
immersion.
PHILLIPS AND SON.
The paint dipping plant at these works, which are situated at
Sherbourne Street, Birmingham, has been in successful operation for
some years past and is applied principally to bedsteads.
The tank holding black japan measures about 5 feet by 18 inches and is
some 9 feet deep. The bedstead head and foot are separately dipped by
hand into the tank which contains black japan, and are immediately hung
on a hook attached to a slowly travelling chain. This chain runs around
a rectangular space, and beneath is a metal lined dripping floor. The
stove is located diagonally from the tank, so that by the time the
bedstead parts reach it the dripping has ceased and they are ready to
be baked. The stoving is done at 320° F., and is continued all night.
One coat is found to be ample.
A very ingenious arrangement is in use for the application of coloured
enamels. Three shallow tanks are mounted on rollers running in angle
irons one above the other in such a manner that any one tank may be
pulled out when required for use free from the others.
As a rule three coats are given for white work and two for green, blue
and most other colours. No white lead is used, but only non-poisonous
colours. The stoving is done mostly overnight at a temperature of 250°
F. A little rubbing down between coats is done with very fine glass or
emery paper. The japans are made by Messrs. Thornley & Knight.
In these works safes are painted, but the work is all done by hand.
THE FORD MOTOR COMPANY.
The extensive works of this company, at Trafford Park, Manchester,
contain as complete a plant for painting, japanning, enamelling and
varnishing, as it has been the pleasure of the author to inspect.
With characteristic thoroughness every detail which will ensure a
first class finish with a minimum of time and labour has been thought
out and applied. The result is that not only is every part dealt with
most expeditiously but one coat of paint is applied to the whole outer
surface of a motor body in the almost incredibly short time of two
minutes. Further details will be found in this book under the heads of
"Flowing-on," "Motor Parts," and "Iron Rods."
MARSHALL, SONS & CO., LTD.
This well-known firm of agricultural implement manufacturers have a
large dipping plant at their Gainsborough works, which they employ
for painting various agricultural machines made principally of red
wood. Some idea of the extent to which this process is applied may be
obtained when it is said that on an average nearly 5,000 pieces pass
through the dipping plant every month. The process is particularly
well adapted for threshing machines and for appliances of the kind
which consist of thousands of holes bored in the wood. If the painting
were done by hand it would take many hours to paint such a machine,
while by dipping it is done even more effectually in a few minutes.
The priming coat only is dipped after knots, etc., have been treated
with shellac. The tank measures 21ft. long by 7ft. deep and 2ft. 3in.
in width. An agitating apparatus is used and the lifting is done by
pneumatic appliances.
HAYWARD BROTHERS AND ECKSTEIN, LIMITED.
The paint dipping plant in use at the works of this firm, at Union
Street, Borough, S.E., is of a comparatively simple type, and consists
of a shallow tank in which various cast iron and steel goods are dipped
in horizontal position. As a rule, one coat of paint is given, but in
certain cases two are required. The bottom of the tank is slanted,
and the contents are stirred up from time to time, but no agitating
apparatus is used. The principal goods painted by dipping are the
frames of Hayward's lights, which are of cast iron and are dipped on
one side only, the other side, after the glass is fitted, being done
by hand. Metal casements are also dipped in considerable numbers, as
well as treads and rises of circular staircases, straight staircases,
balconies, etc. These, being made of ornamental open ironwork, contain
a large number of small shaped holes, and the dipping process is found
to be by far the most effective.
Another speciality of this firm are Hayward's patent steel collapsible
gates. The first coat of paint is applied by dipping; this paint, being
black, dries flat, i.e., without gloss.
THE CRITTALL MANUFACTURING CO., LTD.
These works are at Braintree, Essex, where a large amount of structural
steelwork is produced, the chief manufactures being metal windows
of all kinds, from the well-known steel casement and sash to metal
windows for use in industrial dwellings and specially designed windows
for various climates, steel fireproof doors, skylights, steel office
and works partitions, shop fronts; frictionless ball race runners for
sliding doors, etc.
[Illustration: Fig. 30.--WAGON STORE ROOM, WOOLWICH ARSENAL.]
[Illustration: Fig. 31.--DIPPING CASEMENTS AT THE CRITTALL
MANUFACTURING CO.'S FACTORY, BRAINTREE.]
Perhaps the most noticeable feature of these works as far as our
subject is concerned, is the very complete system of overhead rails,
by means of which the various metal goods produced in the different
finishing shops are conveyed to one or other of the paint tanks and
then, having been left to dry, are taken to store rooms ready for
instant shipment. These rails facilitate handling of the various
goods, and reduce the actual expenditure under this particular item to
a minimum. The rails are L-shaped, the hanger used for each article
or series of articles being of a simple character, consisting of two
wheels bearing on the top of the upright flange, while rods secured by
bolts pass through the horizontal flange and hold it in position.
We will first describe the tank used for dipping metal windows. This is
15ft. long by 12ft. deep and only 1ft. 6in. wide. Attached to the tank
is a large dripping floor measuring some 15ft. by 21ft. covered with
sheet iron and inclined toward the tank, so that the paint which drips
on to it finds its way back into the tank through a grating provided
for the purpose to take off any dried particles. The paint used in
this work is made by Messrs. Docker Brothers, and weighs 13 lbs. to
the gallon; one coat is found sufficient for the purpose. The sashes
or casements being brought in from the finishing room on the overhead
rail, they are lowered into the tank by means of a special lowering
apparatus designed on the premises. Some idea of this may be had from
Fig. 31. In order to keep the load steady during the time it is being
dipped, a slight depression or dip in the rail is made immediately over
the tank. The sashes are only left in the paint for a few seconds, and
are then raised, allowed to drip over the tank for perhaps a minute
or two, and then allowed to drip over the adjacent floor for perhaps
a quarter of an hour or less. They are then taken farther along and
the paint dries in about three hours. Sometimes two, four, six, or
even eight casements may be dipped at the same time. Attached to the
elevating and lowering apparatus are hooks which pass through one
corner of the casements. This causes the parts to hang at an angle
which facilitates running off of the paint.
We come now to the department in which the baking or stoving enamel is
used as applied to metal furniture in general, as mentioned. In this
case the articles are dipped in a manner very similar to that already
described, excepting that a large hook, similar in shape to that shown
in Fig. 32, is used to support the article to be dipped; the wide
opening goes inside the box or file and holds it at an angle so that
when it is lowered into the paint all parts are covered inside and
out. A few minutes are allowed for dripping, and after two or three
hours the articles are ready to be stoved. In this case, Messrs. Docker
Brothers' standard colour, a very pleasing dark green, is used. The
stoving takes three hours at a temperature of 240° F., or higher in
some cases. The tank mentioned is, of course, considerably wider than
that used for casements. The dripping floor is in this case inclined
toward the centre, which in turn is inclined toward the grating just
outside the tank itself. If necessary, special thinners are added
to bring up the gloss, but, as a rule, this is unnecessary. It is
desirable after the article is dipped to go over it once with a small
brush to remove any drips or runs which may possibly appear.
[Illustration: Fig. 32.--HOOK USED FOR SUSPENDING METAL BOXES WHILE
DIPPING.]
Another very important point to be attended to is to exclude all dust,
and for this purpose the Crittall Manufacturing Co. have erected in
this department screens of wire of the finest mesh over windows, so
that no air can pass into the room without the dust being screened off.
EXCLUDING DUST.
A matter of very great importance, yet one which is frequently
overlooked in painting iron and other goods which are to have a glossy
finish, either air dried or stoved, is to exclude dust from the
apartment in which the work is done. In many engineering shops the
nature of the business gives rise to a considerable amount of dust,
and if this is allowed to enter the paint shop it will be fatal to the
appearance of the painted work, as many specks will inevitably settle
on the work and mar its appearance.
[Illustration: Fig. 33--DIPPING CASEMENTS AT BRAINTREE. NOTE THE NARROW
TANK USED FOR THIS CLASS OF WORK.]
A paint shop is best provided with a concrete floor, and this should be
frequently cleaned. The workmen should wear clean overalls, frequently
renewed, and even so small a matter as keeping the hair, beard, etc.,
clean and free from dandruff should be attended to. The doors are
best if double, and thick felt may be used with advantage in the joints
so as to practically seal the opening when the doors are closed. Air
which is admitted, either through ventilators or windows, should be
strained before entering the building, and for this purpose silk gauze
of the finest mesh is usually employed. In some cases, cotton wool in
addition is placed in such a position that the air must pass through
it before entering the room. If these precautions are taken it will be
found that the quality of the work is greatly enhanced.
It may be observed in this connection that it is important also to
provide means of adequate ventilation of the apartment. Moisture
charged air has a bad effect upon paint work. Extreme heat is
unnecessary, but it is very important that the temperature be
maintained at a uniform rate, say 60° F. If the room in which the
painting is done is very hot, the paint will be affected and be likely
to become too thin for its purpose; while, on the other hand, if the
room or articles to be painted are very cold, the paint or enamel will
have a tendency to congeal. Both of these defects can be remedied, as
already stated, by a good system of ventilation and maintaining the
heat, night and day, at a uniform temperature.
A MODEL DRYING ROOM.
The immense importance of providing a uniform temperature and ensuring
an adequate system of ventilation in the room in which goods are placed
for air drying can hardly be exaggerated. Unless such a system is in
use the actual drying may be greatly retarded and the work stand a
chance of being spoiled.
In connection with some of the plant inspected by the author it must
be admitted that the provision made in this respect falls far short of
what is needed. In one case the work of rubbing down was proceeding in
the same shop, although in a different part, in which various goods
which had been dipped were hanging up to dry. It need hardly be said
that under such conditions it was impossible to keep the work free from
specks.
In other cases the drying rooms were inadequate because of the
inefficiency of doors and windows. These, it may be remarked, should
always be double so as to maintain the heat uniformly.
Every varnish user knows that a draught of cold air which is allowed
to reach a coat of varnish while drying is fatal alike to its
appearance and durability. The result is almost certain to be a case
of "blooming," which to the uninitiated may be described as a film not
unlike the bloom of a freshly coloured plum which comes on the surface
of varnish exposed under such conditions. Those unacquainted with
varnish vagaries are apt to regard this trouble as being the result
of inferior materials used in its manufacture. As a matter of fact it
indicates nothing of the kind because, speaking generally, the higher
grades of varnishes are the most susceptible.
Without doubt the best and by far the most economical plan to adopt
is to have a drying room specially built for the purpose of receiving
the articles to be dried. If constructed on scientific principles this
will not only give a uniform temperature entirely free from draughts
and dust but will considerably expedite the work, thereby allowing of
a quicker delivery of goods and effecting a great saving of valuable
floor space.
The author inspected such a drying room at the works of Messrs.
Pinchin, Johnson, and Co., Ltd., at Silvertown, and a description of
it will doubtless prove of interest. It is built of 5-ply wood and is
about 16 feet square, sufficiently large to hold two full-sized motor
bodies or several dozen perambulators, hand wagons, etc. The actual
size may, of course, be varied according to the size of and number of
articles to be dried. Air is admitted through two ducts situated close
to the floor through fine wire gauze, which is provided with a lifting
cover by which the amount of air admitted may be regulated.
Immediately over the two air ducts mentioned is a coil of steam
pipes which heats the air to, say, 110° F. This, of course, causes
it to rise toward the ceiling, but the angle between the ceiling and
wall is rounded off by a cove, so that the current of heated air is
directed along the ceiling toward the centre of the room where there
is another cove and beneath it a coil of cold air pipes which lowers
the temperature somewhat. Thus is created a constant motion of the air
which may be regarded as the essence of the system.
But there is another very important provision in the shape of an
automatic control. This cuts off the steam when any desired heat is
attained so that when the drying room is filled up at night before the
works close it can safely be left until the morning when the drop in
temperature will not be more than 2 degrees. The steam may be admitted
at, say, 10 lbs. pressure, but as soon as the room is heated from 2 to
2½ lbs. will be found to be sufficient. The actual time for heating
the room to 120° F. is from 15 to 20 minutes.
The speed with which work is turned out by this well-considered adjunct
may be gauged from the fact that a panel may receive one coat of enamel
and two coats of flatting varnish in one day, or four coats of japan in
the same period.
In addition to the advantages mentioned is the most important one
that the drying room renders the manufacturer who is fortunate enough
to possess one quite independent of the weather. In the words of the
inventors and patentees, "one enabled by its use to create one's own
climate."
[Illustration: Fig. 34.--DESIGN FOR SHOW CARD DONE BY SPRAYING.]