The Preparation of Plantation RubberMorgan, Sidney
Science
The Preparation of Plantation Rubber
Morgan, Sidney
Rubber
Bucket-washings should yield a good type of pale rubber if they are
obtained properly. To obtain the maximum quantity of good rubber the
buckets should first be rinsed. A gang should be taken, a small quantity
(say a quart) of water poured into the first bucket, and this dilute latex
used progressively in all the buckets of that gang of tappers. The result
is a fair latex which can be added to the bulk of No. 1 latex, provided it
is free from dirt. Where sheet rubber is being prepared, carefully strained
cup-washings or bucket-washings may be utilised in the dilution of the
latex to the required standard, thus increasing slightly the percentage of
first-grade rubber.
TREE-SCRAP.--As tree-scrap is a naturally coagulated rubber, it should be
expected to show up well in quality. This is usually the case; but from
what has been said of the effect of sun-heat it will be understood that if
trees are not regularly "scrapped," there is a danger that the crepes may
be found to contain tacky streaks due to the inclusion of old scrap which
has been sun-baked. In hot dry weather, on widely planted areas tapped on
alternate days, it has been noticed that scrap remaining for two days often
exhibits a resinous appearance, and feels sticky to the touch.
If tree-scrap is to be made as a separate grade, as used to be the general
custom, care should be taken to see that it is free from bark and dirt. On
some estates where scrap-rubber is paid for per pound collected, it is
usually the rule to insist that scrap shall be washed free from dirt and
picked free of bark. This course is to be commended, but might probably
prove impracticable to the majority of estates. Theoretically, of course,
the operation of machining should rid the scrap of all traces of bark; but
in practice it does not do so.
Some proportion of the tree-scrap is usually found to be heavily oxidised,
and naturally if a crepe of uniform colour is to be obtained these dark
scraps must be rejected, otherwise dark streaks will be formed. Coolies
should be instructed to sort out the dark pieces before arriving at the
store.
BARK-SHAVINGS.--It has been intimated in a previous section that the method
of obtaining and collecting bark-shavings varies with the type of labour
employed.
Where the scrap is removed from the edge of the bark on each occasion
before tapping, the amount of rubber to be extracted from the dry shavings
is very small--so small, in fact, that when the price of rubber is low, it
is doubtful whether it pays to collect and work the material.
On the other hand, where trees are not "scrapped" before tapping, the
bark-shavings and tree-scrap are collected together, and the amount of
rubber derived from the mixture may be 30 to 40 per cent. upon the gross
weight--depending chiefly upon the quality of the tapping (_i.e._, in this
case, the thickness of the paring). Another factor influencing this figure
would be the effect of using an anti-coagulant on the cuts.
Public-domain text, read in full here on John Shaqi.
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