The Preparation of Plantation RubberMorgan, Sidney
Science
The Preparation of Plantation Rubber
Morgan, Sidney
Rubber
1. No coagulum should be left without working for longer than the
ordinary period. Otherwise, the prevailing conditions are very
favourable for the development of the disease.
2. Thin crepe only should be made. The quicker the rate of drying the
less possibility is there of the coloured spots appearing.
3. Crepe should never be allowed to remain folded overnight, and
batches of folded wet crepe should be placed on edge to drain off
surface moisture. The rubber should be hung to dry as soon as
possible.
4. Several species of fungi causing coloured spots have been
recognised, and it has been proved conclusively that it is possible to
infect latex and also fresh coagulum.
5. As far as our present knowledge goes, it appears that infection
takes place chiefly, if not entirely, by means of the latex in the
field-vessels. It may take place during transport also, or even during
coagulation.
6. While it is certain that infection can be caused by contact, it has
not yet been shown that infection of the finished wet rubber takes
place in the drying-houses by means of air-borne spores--at least,
under ordinary drying conditions.
7. There is reason to believe that no further infection takes place
once the rubber is well into the drying stage, and that dry rubber is
not infected even by contact. From this one might infer that, as long
as rubber remains dry, infection cannot take place during the voyage
to the port of consignment.
8. Coloured spots do not appear until the rubber is about half dry,
because that period is necessary for the development of the fungus to
that stage in its life-history when it excretes colouring matter. The
fungus in its earlier and colourless stage may have been present from
the time the latex entered the cup.
9. The natural habitat of the fungi would appear to be decaying
vegetable matter in the field.
10. Finally, if it is found impossible to be rid of fungoid-spot
disease after having exercised all care and observed all known
precautions, nothing remains but to supersede the ordinary drying
process by some system of quick drying, such as the vacuum-drying
process or a hot-air draught system, in which the rubber dries so
quickly that any possibility of appearance of "spots" is entirely
removed.
SURFACE MOULDS OR MILDEWS ON CREPE RUBBER.--Defects of this nature are most
uncommon in the higher grades of crepe rubber, but cases of affection in
the lower grades are not rare.
It will be evident from all previous discussions that the incidence of
these moulds must be due to an extremely slow rate of drying. The necessary
conditions would be supplied by one or more of the following causes:
(_a_) Making the crepe too thick.
(_b_) Hanging the crepe in a badly ventilated or badly situated
building.
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