Modern Installation.—As an example of a modern installation of coagulating tanks, we can do no better than offer reproductions of the system now in use on Pataling Estate.
A warning must be given against employing all tanks of stone-ware or cement unless well glazed. Almost without exception, irrespective of the material used in the construction of coagulating tanks, wooden partitions are employed. In the few exceptional cases the partitions are either of glass or of aluminium. The former would appear to be the ideal substance, were it not for initial cost and loss by breakage. These disabilities may possibly be overcome in course of time.
Care of Tanks.—The use of aluminium would have been wider had it not been for lack of supplies and the question of cost during the War. A novel method of employing aluminium partitions was introduced in the factory of Tremelbye Estate. There were no slots in the sides of the glazed-tile tanks, but the necessary slots were very ingeniously created by means of aluminium “distance-pieces,” the two long edges of which were turned at right angles to the face of each piece to a depth of about 1⁄4 inch. The ends of the thin aluminium partition moved in the slot thus formed between two adjacent “distance-pieces.” The friction between the surfaces was sufficient to allow all the partitions, when in position, to be raised well above the floor of the tank, so that a uniform level of latex was obtained. Slight hand-pressure only was then required to push the partitions down.
Naturally the cleansing of glass or aluminium partitions presents no difficulty, but in the case of wood failure to ensure thorough cleanliness leads to possible defects in the finished dry rubber. Provided the wood could be made waterproof, no trouble would ensue, and hence various measures have been tried with that object in view. When new the boards have been surface-waxed or varnished, and the treatment has been repeated on occasions. But in course of time the surface film of waterproof material has disappeared, partially or wholly, and the trouble recurs. When partitions become sodden with serum, the surfaces are liable to be coated with a slime, consisting largely of organic growths which have an effect upon the latex, causing “pitting” on the surface of the coagulum and enclosed bubbles within.
Another Battery of Tanks, without Dilution Tanks or Means
of Gravitating Latex.
It is recommended, therefore, that wooden tanks, after ordinary cleansing daily, should be swabbed out with a 5 per cent. solution of sodium bisulphite. Wooden partitions should receive the same treatment, and once a week at least (or every day if possible) they should be placed in the sun for an hour or two, care being taken that both sides of a partition are exposed in turn. Before being placed in the latex, all wooden partitions should be made wet on the surfaces.
Some years ago the writers had made a partition of vulcanite, which apparently would have proved of great service but for the initial cost. The advent of the War put the matter out of the question, but it is possible now that such a material would be worthy of extended trial. Except in the matter of cost, it would appear to have advantages over any substance yet tried; and if it were possible for estates to supply their own lower grade rubbers direct, the cost might be reduced considerably.