_PRELIMINARY TREATMENT OF LATEX_
RECEPTION OF LATEX AT THE STORE.--Bearing in mind the remarks in Chapter
VI. on the conditions under which latex is transported, it follows that
nothing but the very best and most suitable vessels should be used in the
store. A point to which adequate attention is not given in many factories
might be mentioned here. Considering the importance attached to colour in
the dry rubber by brokers and consumers, and knowing how extremely trivial
are the causes which may mar the colour, it is rather surprising that
better provision is not made for the reception and handling of latex in
factories. Too often the receiving vessels are placed on the floor of the
store close to the entrance. Coolies bringing in latex cannot avoid
bringing with them quite a considerable amount of dirt. Presuming that a
hose-pipe has been installed, and that the floor is constantly being
sluiced down with water, no great harm will result. But would it not be
ever so much better if the dirt were kept out? In how many factories is
provision made for this? Such an arrangement is not difficult to make, and
is already in practice on a few estates. A verandah is built outside the
wall of the factory and all latex is received there. In another place open
chutes are provided which terminate in the straining sieves. The coolie
thus stands on the verandah where he removes coagulated lump and impurities
from the latex, which is then poured down the chute, passing through the
sieve into large coagulating jars or tanks.
Too often it would appear, from the writers' observation, there is a lack
of adequate supervision on the arrival of latex at the store. Much can be
learned from an inspection of the coolies' buckets, and the cause of small
defects in the finished rubber can often be thus traced. Leaves, stems,
bark-shavings, and dirt appear in the buckets, and it is a source of
constant surprise to imagine how even unintelligent coolies can allow such
things to happen. These objects are removed before or during straining, but
still they ought not to be there in the first place, and the fact that such
a state of things exists is evidence of neglect on the part of the coolies
or lack of supervision. Efforts are made in a large number of cases to cope
with these troubles, but on some estates things are allowed to proceed in
the same slipshod way, and too much responsibility is thrown on the
straining process.
[Illustration: RAISED VERANDAH FOR RECEPTION OF LATEX; LIKEWISE EQUIPPED
WITH FACILITIES FOR CALCULATING INDIVIDUAL DAILY "YIELD PER COOLIE" BY
SAMPLING OF LATEX.]
It is suggested that it should be the business of a European to supervise
the reception of latex every day. This is at present quite impossible on
some estates, but it does not alter the fact that this supervision should
be provided, and is extremely necessary.
It is surprising how the point is overlooked in many factories--not that
they are in a dirty state, but they fall short of being classed as clean
factories for want of the little that makes the difference. Possibly those
in charge do not believe that all this fuss need be made, but the writers
can assure them, from a practical knowledge of a very large number of
factories, that cleanliness does pay.
It might not be credited to Tamil coolies, but yet it is probably true,
that the moral effect of working under the cleanest and best conditions has
an influence upon the store coolies, and that their work is better in
consequence. Everything which will tend to simplify the cleansing of the
factory should therefore be installed. Hose-pipes, glazed tiles, clean
floors, plenty of light and air are not fads or fancies, but considerable
factors in determining the final quality of the rubber. There is
considerable truth in the suggestion that the coagulating room and machine
room should be as "spick and span" as a modern home dairy.
STRAINING OF LATEX.--This is a most necessary process, and one which
usually entails much trouble and time which one could wish avoided. It will
be admitted that the trouble could be reduced greatly if the regulation of
field processes could be made more stringent. In spite of knowledge that
impurities must not be allowed to enter the cups, coolies will ignore the
rule that the cup must not be placed in position until the bark shaving has
been cut. The result is that pieces of bark fall into the cups, and coolies
are generally too careless or too hurried to remove them.
Again, when cups are placed on the ground, it is easy to see that dirt may
adhere to them. In the collection of latex some of this dirt may fall into
the bucket. Since the introduction of cup-holders on many estates the
trouble from this source has decreased considerably, but, nevertheless, it
may be taken for granted that even under the best of conditions all latex
requires straining.
The best type of strainer has yet to be evolved. Usually it consists in
principle of a piece of fine brass mesh contained in some form of holder.
Theoretically such a strainer should work well, but in actual practice
nearly all strainers are a source of continual worry. Undiluted latex, as
received at the factory, is of a rich consistency, containing very fine
particles of dirt and often minute particles of prematurely coagulated
rubber. The latter soon clog a fine mesh strainer, while the former may
pass through. When the flow through the strainer becomes slow, the coolie
in charge generally rubs the top surface of the sieve with a piece of
coagulum, thus forcing material through the mesh. He then rubs the
under-surface, with the result that undesirable matter falls into the
strained latex. In theory it seems a simple matter to have a number of
sieves ready so that a clean one may be substituted for a clogged one,
which should be cleansed at once with water. In practice the factory coolie
will probably only carry out instructions when the eye of the
superintendent is alert. As a result of the rubbing and consequent strain,
the brass mesh usually breaks away from its support and the fracture may
not be detected for some time, during which irreparable damage may have
been done to the resultant rubber.
In view of the presence of the fine particles of dirt, to which allusion
has been made, fine sieving of the latex appears to be essential,
especially when sheet-rubber is to be prepared. The fine sieves are
generally of the type known as "60 mesh," and they do not usually give
thoroughly satisfactory results even when the gauze is supported and
strengthened by means of cross-wires placed underneath. The general fault
with these strainers is that a sufficiently wide "selvage" is not allowed
in the clamped edges of the gauze, or that the edges of the support are so
sharp and abrupt that the strands of the gauze are soon severed by the
strain imposed in vigorous cleaning.
Many estates use two strainers; the first a more robust one containing "30
mesh" gauze, and the second the fine "60 mesh." Even this device does not
bring about the desired immunity from trouble. Relief could be obtained if
the latex were always in a more freely fluid form. Estates employing
anti-coagulants in the field benefit in this respect. Other estates,
although finally using the finest of mesh, experience far less trouble than
most estates by reason of a difference in method of working. This can be
explained by an outline of the system adopted on a particular estate:
(_a_) On arrival of the rich latex at the store, all visible
coagulated lumps and other extraneous matter are removed by the
tapper.
(_b_) Each tapper's latex is diluted with a quantity of water.
(_c_) The diluted latex passes through two sieves, one above the
other. The top sieve is of stout perforated zinc sheet, with 10
circular holes to the inch. This removes all large particles. The
lower is of "30 mesh" brass gauze, and practically no rubbing is
required. The latex is now in glazed-tile tanks, in which it is
further diluted to the required standard by means of a recording
instrument.
(_d_) The latex flows by means of a chute into the coagulating tanks,
passing through a large "60 mesh" sieve.
It is not guaranteed that this method will furnish a complete absence of
very fine particles of dirt in sheet rubber, as the human element enters so
largely into the question; but it can be stated that no complaints have
been received on the point of "specks of dirt" since this system was
inaugurated.
On the same estate fine sieving in the preparation of pale crepe has been
abandoned as an unnecessary refinement. The two coarse sieves mentioned
above are employed only, and it is to be acknowledged that the results
justify the procedure.
BULKING OF LATEX.--Not long ago advanced estates used to combine all latex
before coagulation, in order to obtain uniformity of product. Previously it
had been the custom to deal only with comparatively small separate volumes
of latex, with obviously great disadvantage.
Since the introduction of instruments such as the "Metrolac," by means of
which any volume and all volumes of latex may be reduced to a common
standard of dry rubber content, the necessity for "bulking" has passed. It
is not now necessary to keep latex standing, perhaps for two hours,
awaiting the arrival of other latex from distant fields.
STANDARDISATION OF LATEX.--In modern practice, as already pointed out, it
is possible now to handle any volume of latex with a view to its reduction
to any required standard of dilution for the purpose of obtaining a
uniform product. For the reception and subsequent handling of the latex
various schemes have been devised, and they are usually planned in
connection with coagulating tanks used in the preparation chiefly of sheet
rubber.
[Illustration: END-SECTION SKETCH OF VERANDAH, ETC., SHOWING A GOOD METHOD
FOR RECEIVING LATEX AND FILLING TANK.
T, Sheet coagulation tank; C, cylinder for reception and dilution of latex;
GG, gutter; PP, raised platform on verandah; SS, steps leading to platform;
W, dwarf wall; EE, expanded metal partition; OO, open.]
In the successful working of a tank it is necessary, in order to obtain the
best results, to standardise all latex. This cannot be effected properly in
the tank itself, and hence it is the practice to dilute each lot of latex
to standard before it is run into the tank. In the ordinary way this would
entail a great deal of labour in handling the diluted latex. To obviate
this, the scheme outlined in the accompanying sketch has been suggested on
several occasions and in various quarters. Such a scheme or modification of
it has been put into successful practice on several estates. Although the
drawing was made some considerable time ago when estates were not then
prepared to go so far in this direction, subsequent modifications show only
minor differences which, while leaving the original principle intact,
testify to a fertility of resource in adapting the idea to existing
circumstances and buildings. The drawing is _in toto_ almost a replica of
the original installation now in successful use on the Kinrara Estate of
the Ledbury Rubber Company. On this company's Ledbury Estate likewise a
similar system is employed, except that the reception verandah is part of a
natural formation and needed no such direct raising. Several other estates
have now adopted the scheme, which has been proved to be of practical
value. The writers make no claim to originality in the idea, which might
have occurred to many independently on the introduction of coagulating
tanks.
[Illustration: RAISED VERANDAH FOR RECEPTION AND HANDLING OF LATEX.]
VERANDAH.--In reproducing the drawing it is believed that the sketch will
convey practically all the information required. It may be explained that
the coolies are allowed to enter only the outer part of the verandah. The
buckets are handed across the low wall into the care of factory coolies,
who strain the latex through gauze sieves into the latex cylinders.
LATEX RECEPTION VESSELS.--These cylinders may be similar to the tanks
commonly used for transport of latex from distant fields to the factory. An
80-gallon cylinder is easily mounted by its trunnions on a suitable iron
framework which is superimposed on a skeleton truck.
[Illustration: ANOTHER SET OF DILUTION TANKS ON RAISED VERANDAH.]
The latex is diluted down to standard in the cylinders, the truck is moved
opposite the compartment to be filled, and a light movable gutter is placed
beneath the vent of the outlet pipe. This pipe is fixed in the bottom of
the cylinder, and is provided with a large stop-cock which is operated by a
spanner key. The stop-cock should be of the simplest type, capable of being
taken apart and assembled in a minute or so. The orifices should be large
enough for a coolie to insert at least two or three fingers so as to
facilitate cleaning, and the pipe should have no right-angle bends.
On the inside of the cylinder a scale of gallons may be painted, so that
one may possess a knowledge of the quantities run into, or required for the
completion of, any compartment.
A SCREW PLUG UNSATISFACTORY.--It may be of benefit to managers who
contemplate such an installation to know that the adoption of a stop-cock
in the vent pipe of the cylinder is the outcome of experience. In one
instance the vent pipe as designed was fitted with a screw plug at the end.
Unfortunately with this arrangement the flow could not be regulated, and
owing to the "head" of the latex it dashed violently down the gutter,
struck the bottom of the coagulating tank, and thence was scattered over
the factory.
ANOTHER INSTALLATION.--In another type of installation, in place of the
vessels travelling upon a raised verandah platform, the standardised latex
is conveyed to the coagulating tanks by means of drums supported by hooks
to a chain-block and pulley which travels on an overhead gantry. This
method is practicable, but may be regarded as less satisfactory in general
working than the verandah method of treatment.
A MODERN INSTALLATION.--In the most recent scheme for dealing with the
reception of latex, its standardisation, and conveyance to the coagulating
tank, the main principle of the first system outlined is retained; but the
receptacles are not mobile. Glazed-tile tanks are employed, the capacity of
each being approximately equivalent to that of each unit coagulating tank.
The accompanying illustrations show the general arrangement and some
details of the system of reception tanks employed on the well-known
Pataling Estate.