The Preparation of Plantation Rubber Part 4

Note uneven surface and callosities.]

[Ill.u.s.tration: ANOTHER EXAMPLE SHOWING THE EFFECTS OF PREVIOUS TAPPING.]

WATER IN CUPS.--Much discussion used to take place regarding the necessity or otherwise for placing a small quant.i.ty of water in the cups when tapping. It was recognised that the permission to use water (with the idea of preventing coagulation) led to much abuse, apart from the question as to the utility of the method. Dirty water was often used, although clean water may have been placed in the buckets when coolies left the muster-ground.

The small quant.i.ty of water often exceeded the actual yield of pure latex by hundreds per cent., with the result that on arrival at the factory the diluted latex was below the standard desirable for the preparation of a good sheet-rubber.

PREMATURE COAGULATION.--Other opinion to the contrary it is now generally acknowledged that the possibility of premature coagulation in the cup or bucket is at least not diminished by the addition of even clean water. The use of water often obtained from estate drains clearly led to increased trouble. The extent to which such premature coagulation takes place varies greatly under the influence of many factors--_e.g._:

(_a_) Cleanliness of cups and spouts (the latter an important item often overlooked, and involving the presence of certain organisms which effect coagulation).

(_b_) Climatic conditions.

(_c_) Rate and volume of flow of latex.

(_d_) Size of tappers' tasks (involving the length of interval between tapping, and the collection of latex).

(_e_) Distance to be traversed between the site of the task and the store.

(_f_) Care in collecting, to exclude extraneous matter.

(_g_) Nature of transport; agitation of the latex to be reduced to a minimum.

(_h_) Nature of the soil, and situation of the estate.

The last mentioned factor is of great importance. As a general rule it is noted that premature coagulation is less marked on estates situated on comparatively hilly land. The greatest effect is remarked on estates situated on the flat lands of the coastal area where peaty soils are a feature. On many such estates, in spite of the observance of all ordinary precautions, it is not possible to receive the latex at the factory without a large percentage of prematurely coagulated rubber being found in the transport vessels.

ANTI-COAGULANTS.--For this reason on these (and other) estates, the use of small quant.i.ties of anti-coagulants is common. The effect of these is to keep the latex liquid and thus render possible the preparation of a higher percentage of first-grade rubber than would be otherwise obtained.

Among the better known agents which have such an effect upon latex, formalin and sodium sulphite (not bisulphite) are the chief. The latter is the more popular as it is slightly cheaper and much more stable. As now used, it is in the form of an easily soluble powder (anhydrous sodium sulphite). The ordinary crystalline form of sodium sulphite as used in photography is not recommended, on account of its comparative lack of power and its poor keeping qualities.

It will be obvious that, given two equal quant.i.ties of different latices, different amounts of an anti-coagulant may be required to produce the same effect. Hence it should be remembered that a formula which suits the needs of one field or one estate will not necessarily prove suitable in the case of another field or estate. Unless this point is appreciated trouble may ensue. On some estates it has been the custom to give equal quant.i.ties of sodium sulphite solution to all coolies irrespective of the ages of the trees in the fields to be tapped. Thus it happened that the latex from one field was found to have insufficient anti-coagulant present, while that from another field could only be coagulated by the addition of an excess of acid. In this matter the experience of the preliminary trials should have caused some discrimination to be exercised as to the quant.i.ties of solution to be issued in each field or division. It has been found sometimes that a moist glossiness in the smoked sheet could be attributed to the use of an excess of sodium sulphite. Traces of the salt remained in the rubber, and as the substance is hygroscopic, moisture was being absorbed from the air, to cause a surface deposit which often returned even after the sheets were surface-washed and re-dried.

If sodium sulphite is to be used in the field, the following formula, which is in wide use, may serve as a basis for trials.

_Formula for Use of Sodium Sulphite in the Field._

(_a_) Dissolve anhydrous sodium sulphite in water at the rate of 1 pound to 3 gallons.

(_b_) Of this solution each coolie is given about 3/4 pint. This is usually sufficient for a task of 350 trees. The solution is used by shaking a few drops into the cup or, diluted with an equal volume of water, it is run down the main channel when the latex flows.

[Ill.u.s.tration: 1. SHOWING EFFECT OF "WINTERING."]

On some estates it is found either unnecessary or impracticable to use the solution in this manner. Instead the anti-coagulant is placed in the bottom of the bucket prior to the commencement of collection. The solution is made as in (_a_) above, and roughly half an ordinary latex-cupful is placed in each bucket.

[Ill.u.s.tration: 2. NEW GROWTH OF YOUNG LEAF ON SAME TREE.]

COLLECTING PAILS.--All vessels intended for the transport of latex should have a smooth and curved interior, so that cleansing may be easy.

Preferably the interior and exterior surfaces should be glazed, but it is often found that the enamel chips easily, and that the handles are too frail in construction. The shoulder-pieces, to which the handles are joined, are often too lightly attached to the bucket. Something stouter in the shape of enamelled ware is required, without an appreciable increase in weight. Until such a utensil is available, the heavily galvanised and bra.s.s-bound milk-pails used on some estates are as good as anything at present in vogue, providing they are kept scrupulously clean.

[Ill.u.s.tration: EFFECTS OF DISEASE--"MOULDY ROT."

(_a_) Note on right hand the panel next in order for tapping; a hopeless position.]

[Ill.u.s.tration: EFFECTS OF DISEASE--"MOULDY ROT."

(_b_) The present cut badly infected; above there is no renewal of bark.]

The collecting pails should be kept under cover, when not in use, either at the muster grounds or at the factory. On some estates coolies are allowed to take them to their quarters, where they are used for various purposes.

Curious effects of this practice have sometimes been noticed. As an example might be quoted an instance in which premature coagulation was found to take place to a surprising degree. It was discovered eventually that the coolies (Javanese in this case) were in the habit of utilising the buckets for the preparation of their food. A liquid extract of a popular fruit was often made. This extract was very markedly acid in character, and as the buckets were not afterwards thoroughly cleansed, the latex of the following day suffered.

[Ill.u.s.tration: EFFECTS OF DISEASE--"MOULDY ROT."

(_c_) As in (_b_); another tree.]

Preferably all buckets should have a lid of slightly funnel shape. This is inverted during collection, and thus prevents much dirt falling into the latex.

[Ill.u.s.tration: EFFECTS OF DISEASE--"MOULDY ROT."

(_d_) At close quarters. Note wounds due, apparently, to bad tapping, but really caused by the disease.]

PAYMENT BY RESULT.--The arguments for and against the inst.i.tution of this practice are many. In actual result there can be no question that a higher yield is obtained by the adoption of a scheme under which the coolie is either given a bonus based on result or is paid at a definite rate per pound. It is fully recognised, both by advocates and opponents of payment by result, that the personal equation of the tapper is a very important factor. A good skilled tapper will always obtain a higher yield than an ordinary individual from the same task of trees, and without any more injury to the trees. It is argued, therefore, that such an operative should be given the benefit of his skill. Apart from this, it is claimed that even the average tapper does not do his best work if he knows that he will get his daily wage, no matter what his yield may be, as long as he does not injure the trees by wounding. It is claimed that this sense of security leads to shallow tapping which, while it has an agreeable appearance, does not produce the available amount of rubber.

On the other hand, it is advanced in opposition that under a scheme of payment by result the tappers' only consideration is the matter of obtaining rubber, and that considerable damage in the form of wounds is done by over-deep tapping. That there is a great deal of truth in these statements is not to be doubted. Much, of course, depends upon the amount and quality of the supervision possible, and upon the standard demanded. It is a notable fact, however, that on estates which first introduced the system some years ago the quality of the tapping compares favourably with that of average estates, and in a few instances within the experience of the writer the tapping is of a high standard. Possibly these are exceptional instances, and there can be no doubt that the opposition of many managers of considerable experience is founded upon the deterioration in the standard of tapping which often follows the inst.i.tution of payment of tappers by result.

It will be recognised by planters that apart from the personal factor in tapping, the worker might be so unfortunate as to be placed in an area from which the yield is naturally low, either by reason of its youth or from other natural causes. Obviously such individuals are ent.i.tled to special consideration in respect of the rate per pound paid for the rubber obtained. Again, on very hilly land it may be not humanly possible for a worker to tap the usual number of trees. Hence to place him on a parity with other tappers, as far as wage-earning capacity is concerned, a higher rate than ordinary must be given. It will be plain, therefore, that on any one estate it is generally impossible to set a standard rate per pound for payment by result; the rate may vary, for example, from, say, 3 cents per pound in old and high-yielding tasks to 12 cents or more per pound on young areas of the same estate.

Naturally the actual rates paid will primarily depend upon the average yield per tree or yield per acre, and the lower the average yield the higher the rates to be paid per pound. Thus, on low-yielding properties where the natural conditions render a high yield impossible the rate per pound may reach a figure of 22 cents (approximately 6d.).

The methods of arriving at the yield of rubber brought in by individual tappers vary, but broadly they fall into two cla.s.ses:

(_a_) That in which the volume of latex is ascertained (either by measuring or by weighing), a sample is drawn, and the final calculation made from the weight of the more or less dry sample.

(_b_) That in which, after noting the volume, the calculation is based upon a reading of the dry rubber content of the latex, obtained by means of an instrument such as the "Metrolac," or any other instrument working on the same principle.

Quite a number of estates which have not adopted the full system of payment by result yet employed some such method of checking the yields of individual coolies, as the observed results act as a great deterrent against various malpractices, such as neglecting to tap trees, adulteration of the latex, etc.

TREE-Sc.r.a.p.--The thin film of latex which coagulates naturally upon the surface of the tapping cut after the latex has ceased to flow is known as "tree-sc.r.a.p." Normally it is collected on all estates, but the method of collection varies according to the cla.s.s of labour employed. On most estates, where the labour is Tamil or Javanese, it is supposed to be removed as fully as possible before the tapping cut is reopened. The narrow strips are then placed in a bag or basket carried by the tapper. Chinese tappers usually decline to follow this practice of first peeling off the sc.r.a.p, and remove it by the operation of tapping, with the result that the sc.r.a.p when brought into the store has adhering to it various shavings of bark. Unless these can be thoroughly cleaned off the sc.r.a.p cannot truly be cla.s.sed as "tree-sc.r.a.p."

OXIDATION OF TREE-Sc.r.a.p.--It is often noted that some sc.r.a.p is dark in colour, and in this condition it is generally spoken of as "oxidised"

sc.r.a.p. The oxidation is probably due to an enzyme, and also to the presence of chemical substances of a phenolic nature. In the course of laboratory experiments with normal latex, it was found possible to reproduce this darkening due to oxidation by the addition of very small quant.i.ties of various phenols used in general chemical processes, and the rapidity with which the darkening was effected depended upon the quant.i.ty of the phenol added. If this rapidly oxidising latex be mixed with normal latex, it would seem that the whole bulk of the latex is affected by this tendency to rapid oxidation. It is observed that this condition under which any tree may yield rapidly oxidising latex is not a permanent one.

CARE OF TREE-Sc.r.a.p.--As these sc.r.a.ps eventually give a grade of rubber which compares well with other and better-looking grades care should be exercised in collection and treatment so that its quality is not impaired in any way.

TO PREVENT OXIDATION.--As a rule the sc.r.a.ps are picked over, and heavily oxidised pieces are sorted out; otherwise the crepe rubber prepared exhibits black streaks. The sc.r.a.ps should not be allowed to remain in the sun (which induces "tackiness"), and if they have to be kept over night they may be placed in a weak solution (1 per cent.) of sodium bisulphite to arrest oxidation. It should be recognised that such a solution will not "bleach" already darkened sc.r.a.p-rubber, and the nature of its action is only anti-oxidant.

BARK SHAVINGS.--In the matter of collecting bark-shavings much depends upon the organisation and nature of the labour force. Probably, on the majority of estates bark-shavings are collected systematically, but on quite a number considerable laxity in this respect has been noted. This may arise from lack of adequate supervision or from the peculiar systems of working which seem to pertain to Chinese labour. Granted that the trees are well "sc.r.a.pped," and that the percentage of rubber obtained from shavings under such circ.u.mstances would be extremely small (say 2 per cent. by weight on the total output), it does not need much calculation to see that annually the loss of rubber to the estate must be considerable. It would also seem to follow that, if the adult labour declines to pick up bark-shavings carefully, it might pay to employ children for the purpose. Or, as is done in some places, the adult labour might find it advantageous to collect bark-shavings at low rates per pound.

It is a well-known fact that if bark-shavings be allowed to acc.u.mulate in a heap for any but a short period, a fermentative and heating action is set up. The heat developed in these piles of shavings is so considerable that it is impossible to keep the hand in a heap for more than a second or two.