The Preparation of Plantation Rubber Part 5

Should this be allowed to persist, as would happen in the case of a breakdown of engine or machines, it usually results in the final crepe rubber becoming tacky when approaching dryness.

To avoid this heating effect it is necessary to have spare jars or proper tanks in which the shavings may be soaked in water. In this condition bark-shavings may be kept for many days.

For the same reason (_i.e._, the heating effect and consequent tackiness) the custom followed on some estates of allowing coolies to keep bark-shavings in their "lines" until they have acc.u.mulated a fair quant.i.ty cannot be commended, quite apart from the possibility of actual loss by theft, which is thus rendered easy.

It will be clear that where the trees are sc.r.a.pped efficiently before tapping, the amount of rubber to be obtained from the treatment of pure dry shavings would be almost nil, and would scarcely repay the cost of collection and working. In actual practice, however, it is not possible to guarantee that the shavings are free from some sc.r.a.p-rubber. Shavings brought in by Tamils and Javanese carry only a small amount of rubber, whereas where Chinese tappers are employed the yield of rubber may be as high as 35 to 40 per cent. upon the total weight of the material treated.

Few estates now are not equipped with "sc.r.a.p-washers"--machines specially designed for removing the bark from the rubber--and if they function efficiently the resulting crepe should be free from bark-particles.

COLLECTION OF EARTH-Sc.r.a.p.--This, the lowest grade of rubber, is found at the base of the tree. Theoretically, if proper precautions are observed, the amount should be comparatively small, but in actual practice it may be very appreciable. The usual contributory causes are:

(_a_) Failure to replace cups beneath the spouts of trees which continue to drip latex after collection.

(_b_) Collection of latex at too early a stage.

(_c_) Failure on the part of the tapper to ensure the flow of latex, by means of the spout, into the cup.

(_d_) Flowing of latex over the edge of the cut before it reaches the vertical channel.

(_e_) "Wash-cuts" on wet days, when the volume of rainwater down the tree is sufficient to wash the latex out of the cup.

The amount of earth-sc.r.a.p collected on any estate will depend, all other things being equal, upon the labour expended in its collection. Certainly on well-organised estates, having ample labour, the amounts collected are huge in comparison with other estates. The ground at the base of the tree below the latex-spout is systematically turned over with pointed sticks and large clots of rubber are often picked up. Here, again, it is advised that the collected earth-sc.r.a.p should not be allowed to remain in heaps upon the floor of the factory. It should be placed in suitable tanks containing water, and quite a considerable portion of the cleansing work is thus taken from the machines.

CHAPTER VI

_TRANSPORT OF LATEX AND COAGULUM_

PERCENTAGE OF FIRST LATEX AND OTHER GRADES.--One of the problems confronting any manager is the question of the percentage of first-grade rubber calculated upon the whole output. Inquiries are constantly being received for advice as to what the various percentages of each grade of rubber should be. This is a question to which no definite list of figures can apply. There are so many little factors influencing the result. Some estates are not particularly careful in collecting tree-sc.r.a.p. Hence quite a quant.i.ty of tree-sc.r.a.p finds its way into the crepe made from bark-shavings. On the other hand, bark-shavings are not collected systematically on some estates, and the total output is thereby diminished.

In consequence the first-grade rubber shows a higher percentage than it would otherwise. Again, if the earth-rubber is not regularly collected the percentages of the best grades are higher than they should be. In comparing the percentages of each grade of rubber from any two estates, therefore, one should have all the information possible as to the various working details of the estates. Without wis.h.i.+ng to lay down any definite proportions which can be applied to all estates it might be said that, taking averages over a large number of estates, the percentages to be aimed at are:

First-grade latex 75 per cent. to 80 per cent.

Other grades 20 " " 25 "

For these figures one promises that all lower grades are collected and accounted for carefully and regularly. The distribution of the lower grades will depend upon the field practices of the particular estate, but the following list might be given for an estate keeping all lower grades distinctly separate:

First-grade latex 75 per cent.

Cup-was.h.i.+ngs } Coagulated lump, etc. } 10 "

Tree-sc.r.a.p 9 "

Bark-shavings 4 "

Earth rubber 2 "

--- 100 "

Emphasis is again laid on the statement that these figures must not be accepted as a standard. Nevertheless, they may prove of some service to managers in giving an idea of what the general line of percentages may be.

There are special circ.u.mstances, such as distance of transport and the nature of the land, which at present would render the attainment of more than 75 per cent. first-grade rubber impossible on some estates. Still the fact remains that if the percentage is low through distance of transport, etc., some method will have to be discovered by means of which the difficulty maybe overcome. On a few estates the percentage of first-grade rubber obtained sometimes reaches 85, but these results are rather out of the ordinary. An estate which collects all lower grades properly is doing well if the percentage of first-grade rubber is 75 or over.

EARLY COLLECTION.--As already noted in the preceding chapter, one of the factors influencing premature coagulation is that of the interval elapsing between the commencement of tapping and the collection of latex. It will be seen that this ordinarily would depend, in turn, upon such considerations as the size of the tappers' tasks, the s.p.a.cing of the trees, and the natural conformation of the land over which the tappers have to perform their tasks. In general it need only be remarked that every possible consideration should be given to this question, and that any delay should be avoided.

TRANSPORT.--Wherever possible it is endeavoured to convey latex from field to factory by man-power. Tamil coolies, as a rule, place the bucket on the head; Chinese and Javanese coolies like to use a balanced carrying-pole.

Where distance renders these methods too costly in time and labour, it is usual to have field centres where the latex is collected and dispatched to the factory generally (_a_) by means of vessels conveyed on light railways; (_b_) in large cans placed on motor-lorries; (_c_) in cylindrical galvanised drums supported on two wheels and drawn by bullocks. There may be variants, but these are the chief means of transport in bulk over a distance.

Where possible, the best system is that employing a trolley-line, as great agitation of the latex is avoided, and the time in transit is much reduced.

The usual method of transport by bullock power is slow, and as estate roads (and even Government roads) are often below the standard expected in this country, the jolting undergone by the latex is, to say the least, not calculated to afford a high yield of first-grade rubber. The late Mr. F. W.

F. Day advocated the use of a circular perforated wooden grid, to be floated on the latex, in order to moderate the wave effect produced by jolting.

Whatever the means of bulk-transport employed, it should be the care of those in charge to see that vessels are not allowed to remain in the sun longer than is necessary. Even during the journey they should be shaded in the best possible manner.

These large transport vessels usually receive what is really only perfunctory attention in the matter of cleaning. They should receive the same care as would be exercised in dealing with milk cans in other countries. Ordinary sluicing with water is not sufficient, and if they cannot be sterilised by means of boiling water, they should be treated, after ordinary was.h.i.+ng, with a 5 per cent. solution of sodium bisulphite every day.

ANTI-COAGULANT FOR TRANSPORT.--When anti-coagulants are not used in the cups or buckets, it is advisable to use them in the bulk-transport vessels.

Either formalin or sodium sulphite is of service, but the great objection advanced against the former is its loss due to evaporation while the carts are going to the fields or waiting at the centres. For this reason sodium sulphite is now generally employed.

_Formula for Use of Sodium Sulphite in Transport._

(_a_) Dissolve 1 pound of powder in 3 gallons of water.

(_b_) Of this solution, place half a gallon in the vessel for every 30 to 40 gallons of latex.

TRANSPORT BY COOLIE.--As already pointed out, the extent to which man-power can be used in transport of latex is generally limited. On small estates it is an easy matter for coolies to carry the latex to the factory, but on larger estates many difficulties may arise, which may also militate against the successful use of other means of transport. It is not uncommon to find, therefore, that a policy of decentralisation has been adopted.

COAGULATION CENTRES.--Divisions of the estate have their own small stations at which latex is received and coagulated. In this way it is possible to receive latex without much delay, and with benefit to the resultant rubber, especially if prepared in sheet form. Much controversy has arisen regarding these decentralised establishments, but the fact remains that on large estates, which are efficiently controlled, the scheme has been highly successful from all points of view. On the other hand, it is alleged that this method of working increases costs, and often gives an unsatisfactory quality of rubber. Concerning the latter point it seems to be reasonable to expect that the European in charge of any division should be conversant with the method of preparation required, and should be capable of seeing that no mistakes are made. Given uniform equipment in all stations, and uniform rules for treatment of the latex, there does not appear to be any valid reason why the product of one station should be inferior to that of the others. Neither is it so in the case of several estates which might be quoted.

In the matter of costs of working the writer has had to investigate several cases regarding which there was dissatisfaction. In some instances it was found that the stations had not been placed advantageously with respect to a water-supply; and instead of one or two coolies pumping for an hour or two, a larger number had to be employed for hours in the carriage of water from the nearest available source. This meant that, as the coolies were on daily wage, the force appeared to be much bigger than that usually required. In other cases there were too many store coolies, when often the place of some could have been taken for the necessary period by tappers arriving early from the nearer fields. Sometimes costs were increased by reason of the use of an excess of chemicals, owing to the lack of uniform rules throughout the several stations. In spite of all that has been written, and the verbal instructions that have been given, it was not uncommon to find unstable chemicals such as sodium bisulphite exposed to the moist air. In this way not only was there waste of material, but also the probability of inferior rubber being made.

TRANSPORT OF COAGULUM.--On the whole if it is a question between the transport of latex and the transport of coagulum, the writer would always favour the latter, for reasons which have possibly been made clear in the preceding paragraphs. In effect, it should be recognised that the less handling and transport the latex receives the better the general result.

If proper precautions are taken, the transport of coagulum intended for the preparation of crepe should present no difficulty, and should have no injurious effect upon the quality of the resultant rubber. It is only too common, nevertheless, to note defects, in the finished crepes, which can only be attributed to a failure to observe reasonable care in the transport of the coagulum. For example, it has been observed that a ma.s.s of coagulum from a coagulation station has been conveyed on the floor of a bullock-cart, or motor-lorry, previously used in the carriage of other materials. Unless the boards have been most scrupulously cleansed, the coagulum is found to be contaminated, often to a marked degree. Again, although the cart may be clean, it may have to travel some distance on roads carrying a fair amount of motor traffic. Even should the cart have a canopy, road-dust is often whirled through the open sides of the cart; and in the districts where red laterite roads are common, the stain of such dust often persists in the finished crepe. It scarcely need be remarked that coagulum should be transported in closed wooden boxes or in galvanised iron drums fitted with lids; and that preferably sufficient water should be present in these receptacles to allow the coagulum to float. All such containers should receive the same scrupulous attention as the vessels employed in the transport of latex.

The successful transport of coagulum for sheet-making is fraught with much greater disabilities, and it is usual to note on most estates that the resulting sheets from out-stations are always inferior, in final result, to those coagulated and prepared at the central factory. If the flat pieces of coagulum are placed in piles of any height it is common to find, on arrival at the factory, that much adhesion has been caused. There is great difficulty in separating the pieces, and often the successful operation is impossible. It is usual to hand-roll the coagulum before transport, but it is often found that by the time the rubber reaches the factory it has become too hard for subsequent good results.

One of the strong arguments in favour of the establishment of divisional stations is to be found in the preceding paragraph. Sheet-making, as it necessitates the employment of only light machines suitable for hand-power, is a feasible proposition in a field station. There is no reason for sheets made thus to be in any way inferior to those made at a central factory; in fact, they are often better, as the latex has the chance of being treated when comparatively fresh.

If it is found necessary to transport sheet-coagulum, every possible precaution should be taken against piling the pieces.

After hand-rolling some estates bring the rubber from the field-stations to the central factory in drums of water, others in shallow boxes containing not more than half a dozen sheets in a pile. A method proposed long ago, but not in practice, was to have a number of shallow trays subdivided so that each compartment held one sheet only. If these trays were properly made and carefully fitted there appeared to be no reason why they should not form sliding parts of a large box, in which squeezing and adhesion of the pieces of coagulum would be avoided. Naturally any such device would increase appreciably the weight to be transported, and on this ground would not find popular favour except where motor-power is used for road transport.

PART II

FACTORY OPERATIONS