The Preparation of Plantation RubberMorgan, Sidney
Science
The Preparation of Plantation Rubber
Morgan, Sidney
Rubber
It may be found sometimes that only some of the sheets are affected.
This indicates that, whereas uniform quantities of a solution of
sodium sulphite have been served out in all fields, the proportion may
have been excessive in the case of fields giving a latex of
comparatively low rubber content. What suits the latex from old trees
may be excessive probably for the latex of younger trees. This is not
an infallible rule, as in the case of older fields in which immature
bark is being tapped, it is to be noted that the dry rubber content of
latex may be less than that of latex obtained from younger trees.
This type of moist glaze is not easy to remove. Ordinary surface
washing had but a temporary effect, and the trouble recurs. The only
way of dealing with the difficulty is to soak the sheets for days in
running water (or in successive changes of water) and to re-smoke
until dry.
(_b_) The second type of moist glaze is not so difficult to deal with,
and may be removed as a rule by washing the sheets when the rubber is
otherwise apparently dry.
It appears to be mainly a matter of unsuitable fuel for smoking and of
failure to provide adequate ventilation. A large number of estates
have been "thinning-out" or are doing so systematically. The logs thus
obtained are often used as fuel in the very green stage. The smoke
thus generated must be moist, and if the building is entirely closed,
this moisture must be deposited eventually upon the rubber and racks.
Some estates have surmounted the difficulty by opening up the
roof-ridge slightly so as to allow the moisture to escape with some of
the smoke; but if the logs from rubber-trees are to be used, they
should be stacked in the sun for some time. Even then, preferably,
they should not be used alone. A judicious admixture of dead and
rotting jungle-timber appears to give very satisfactory results.
VIRGIN SPOTS AND PATCHES.--If the description really indicates the defect
it simply means that portions of the sheets are not dry. When cut they
exhibit the typical whitish, opaque appearance described as "virgin." It is
doubtful whether any rubber put upon the market as No. 1 product nowadays
can have this complaint levelled at it. In the extreme case it points to
gross negligence on the part of the packer.
Sometimes what are taken to be small spots of "virgin" are really patches
of tiny air or gas bubbles. The point can be easily determined by cutting
through the patch and examining the cut edges.
SURFACE MOULDS OR MILDEW.--During the last two years, complaints regarding
the incidence of "mouldy rubber" (_i.e._, relating chiefly to the presence
of mildews on the surface) have become increasingly common.
Public-domain text, read in full here on John Shaqi.
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