The Preparation of Plantation RubberMorgan, Sidney
Science
The Preparation of Plantation Rubber
Morgan, Sidney
Rubber
MICHIE-GOLLEDGE SYSTEM.--The Michie-Golledge system comprises a process of
preparation and drying. The latex is diluted with two, three, or four
volumes of water and coagulated with acid in a vessel which is rotated with
a churning motion. In this cylinder there are curved and fixed blades. The
revolving cylinder and its ribs force the latex against the curved blades
so as to cause an eddy in the middle of the machine. Here the rubber
coagulates and accumulates, the remaining liquor whirling round outside the
blades. It can be imagined that with such dilute latex, the coagulum is
very soft and spongy. This soft mass is passed through a machine which cuts
it into "worms" about 3/16 inch in section. These are placed upon wire
trays and dried by means of hot air. The "worms" when dry are re-macerated
and built up into medium and thick crepes. The colour of the rubber
prepared by this process is usually very good. When treated in a Colombo
drier the "worms" usually require about two hours to dry, so that crepe
rubber may be packed at latest on the fourth or fifth day, as in the case
of vacuum-dried rubber.
RATE OF AIR-DRYING OF CREPE RUBBER.--In spite of the facts that some
estates have been making thin pale crepes for years, and that so much has
been written concerning the preparation of this grade of rubber, one
occasionally meets with a case in which an estate seems to be unable to
prepare thin pale crepe, or if it does the period of drying is much longer
than obtains on most estates.
Again, when cases of infection by spot disease in fairly thin crepes are
submitted, it is usually found that the particular crepes are of that type
which, though fairly thin, show whitish spots of moisture when the bulk of
the rubber is nearly dry. This type of crepe is to be noted for the
excessive period of drying in comparison with other crepes of equal
thinness. It has been advanced elsewhere[12] that a factor of the most
considerable importance in the rate of drying of crepe rubber is the type
of drying-house and its situation. This accounts very largely for observed
differences in the rate of drying of thin crepes on different estates. Yet
even where two drying-houses may be of the same type, and the situations
may be comparable, one still observes that one thin crepe dries more
quickly than another. It has been remarked also that a thin crepe in one
old drying-house dries in a shorter period than a similar crepe in another
more modern house, although the methods of coagulation and preparation
exhibit no apparent diversity. In all these conflicting cases allowance is
made for the weather conditions, and the observed differences seem to be
inexplicable. It has always been the opinion of the writers that the actual
rolling of the rubber plays an important part in determining the rate of
drying of crepe, apart from the question of thinness; and it seemed
possible that this factor would account for the discrepancies noted above,
either partially or wholly.
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