(c) The diluted latex passes through two sieves, one above the other. The top sieve is of stout perforated zinc sheet, with 10 circular holes to the inch. This removes all large particles. The lower is of “30 mesh” brass gauze, and practically no rubbing is required. The latex is now in glazed-tile tanks, in which it is further diluted to the required standard by means of a recording instrument.
(d) The latex flows by means of a chute into the coagulating tanks, passing through a large “60 mesh” sieve.
It is not guaranteed that this method will furnish a complete absence of very fine particles of dirt in sheet rubber, as the human element enters so largely into the question; but it can be stated that no complaints have been received on the point of “specks of dirt” since this system was inaugurated.
On the same estate fine sieving in the preparation of pale crepe has been abandoned as an unnecessary refinement. The two coarse sieves mentioned above are employed only, and it is to be acknowledged that the results justify the procedure.
Bulking of Latex.—Not long ago advanced estates used to combine all latex before coagulation, in order to obtain uniformity of product. Previously it had been the custom to deal only with comparatively small separate volumes of latex, with obviously great disadvantage.
Since the introduction of instruments such as the “Metrolac,” by means of which any volume and all volumes of latex may be reduced to a common standard of dry rubber content, the necessity for “bulking” has passed. It is not now necessary to keep latex standing, perhaps for two hours, awaiting the arrival of other latex from distant fields.
Standardisation of Latex.—In modern practice, as already pointed out, it is possible now to handle any volume of latex with a view to its reduction to any required standard of dilution for the purpose of obtaining a uniform product. For the reception and subsequent handling of the latex various schemes have been devised, and they are usually planned in connection with coagulating tanks used in the preparation chiefly of sheet rubber.
End-Section Sketch of Verandah, etc., showing a Good
Method for receiving Latex and filling Tank.