(f) The skimmings and very dilute latex, coagulated with excess of acid.
Working the Coagulum.—Description of the details of necessary machinery for crepe-making is relegated to [Section III.] of this book. Here we shall treat only of the matter in general.
In the preparation of crepe rubber heavy machinery is necessary, and ample engine-power must be available. The machines should comprise three types:
(a) With rolls cut in such fashion, and run at such different speeds, as to have a macerating effect upon the coagulum. Such machines or rolls will be referred to as “macerators.”
(b) Intermediate rolls, grooved in varying designs and geared differentially. These reduce the thick rough crepe obtained from the macerators into a form suitable for passing to the rolls described in (c). They are sometimes called “crepers,” but as this term may be applied equally to the macerating rolls, they will be termed the “intermediate” rolls.
(c) Smooth rolls usually run at approximately even speeds and, as their name denotes, devoid of any grooving. They are called “smooth” rolls or “finishers.”
Without such equipment it is not possible to prepare the grade which is known as “fine pale crepe.” In the common acceptation of this term crepe of No. 1 quality generally connotes fineness and paleness with a thin crepe which has a good, smooth, and fairly well-knit texture.
It is, of course, possible to make a thick pale crepe, using only the macerators and intermediates, but the “finish” will be that typical of the particular grooving of the intermediate rolls. For the preparation of crepe ordinarily, the possession of smooth rolls is a sine qua non.
For reasons which will be explained more fully in the [chapter] dealing with the defects of crepe rubber, the practice of preparing thick crepes direct from the coagulum is now very uncommon. Thick crepes are generally made by reworking dry rubber, either in the form of thin crepes or from air-dried sheets. The market for the latter in Malaya is confined almost entirely to Singapore, where factories buy native rubber and re-work it into thick crepe.
The bulk of the output of No. 1 crepe from estates is in the form of thin “fine pale crepe.” The artificial standard set up by buyers and brokers necessitates this thin crepe being of even texture and fairly free from small holes (“looseness”). What difference the small holes are to make in the vulcanising properties of the rubber is beyond our knowledge; but such being the standard, it must be attained if the full price is to be obtained.