The Preparation of Plantation Rubber Part 22

_E,E_ the compartments in which the engines are bedded. In these positions it is possible to obtain direct drive to the machines.

_D,D_ are large double swing or sliding doors (the latter for preference always). These, while suiting transport of rubber, provide also for a free draught of air.

If possible the sc.r.a.p-was.h.i.+ng machine should be placed outside the wall of the factory, and tanks for the reception of sc.r.a.p rubbers may then be situated in convenient proximity.

Economy of labour is obtained by grouping all factory buildings as closely as possible, but it should be borne in mind that smoke-houses should be regarded as a possible source of danger from fire. This point has a practical bearing upon rates of insurance, and it is essential that the smoke-house should be situated at a minimum of 50 feet from any other building or group of buildings. In this connection, also, it may be noted, as being of further practical interest, that, in the insurance of smoke-houses, preferential rates are given to those having a good type of slow-combustion furnace.

CHOOSING A FACTORY SITE.--Sufficient has been written to make it clear that the choice of a site for factory buildings is a matter demanding weighty consideration. Much, of course, depends upon the planted area, and the rate at which it comes into bearing. Under certain circ.u.mstances which will be obvious, it is permissible to instal first a group of buildings of a temporary nature only, the future site and permanent buildings to be chosen later when the main portion of the estate comes into bearing. Often, however, one finds that, from lack of forethought, the estate has been committed to considerable expense in the establishment of equipment, which later is proved to be unfavourably situated with regard to the majority of the area in ultimate bearing. In such case, transport of latex is fraught with difficulties and may be expensive.

In the instance of an estate which will gradually come into bearing, it is not easy to decide whether a temporary installation shall first be provided, or whether, in antic.i.p.ation of future demands, a complete equipment shall be erected. So much depends upon the financial aspect of the question, and upon the rate at which areas will come into bearing. As far as is possible, the best policy would be that of a compromise under which the site would suit later requirements, and the factory would be so planned as to be capable of future easy extensions both of buildings and machinery.

It is not possible to lay down any definite data as regards requirements based on acreage, or to make comparisons between any two estates of similar acreage. The important factors determining such requirements are:

(_a_) Area.

(_b_) Shape of the estate.

(_c_) Topography of the estate.

(_d_) Available supplies of water.

Naturally the ideal site for factory buildings would lie in a central position, given other favourable conditions.

CENTRALISATION OR DECENTRALISATION.--It is the experience of a number of estates that, all other conditions being favourable, there is a limit beyond which the centralisation of factory work leads to an unwieldy position. We are not here concerned with the few extremely large estates running into tens of thousands of acres. In those cases the total area would be divided into economic sections. The argument there would resolve itself into a discussion on the size of an economic section. This, in turn, would be dependent upon the type of main product, involving the question of transport of latex or coagulum, and the possible provision of batteries of heavy machinery.

The differentiation between the transport of latex and coagulum, respectively, is a most important one, and has a powerful influence in determination of the maximum of centralisation possible. Whereas properly prepared coagulum may be safely transported by bullock-cart, light-railway, or motor vehicle for many miles, latex, on the other hand, demands very careful treatment. Anti-coagulants may be employed to preserve fluidity, but only within certain limits. Even under these conditions, other factors (chiefly climatic) exert an influence which renders the transport of latex for any distance a matter of anxiety.

It will be plain, therefore, that the limits of centralisation of factory work are much narrower for the preparation of sheet rubber than is the case when crepe rubber is to be made. In actual experience the preparation of a high standard and a high percentage of smoked sheet is attended with considerable difficulty in those cases where the factory processes have been ultra-centralised. Apart from the difficulties inherent to the transport of latex in a state of good preservation, there is the added difficulty of dealing quickly with large volumes of latex brought from various quarters. None of these should be allowed to remain standing if the best results are to be secured; but obviously there must at times be some congestion. Even on a small scale it is often found that the latest batches of latex are unfit for the preparation of good sheet rubber, and the trouble may be easily exaggerated when working on a large scale.

The centralisation of work on crepe preparation, therefore, is limited only to a comparatively slight degree by distance of transport, and in the main only by the size of the necessary equipment of machinery and drying accommodation.

The successful preparation of sheet rubber is, on the contrary, governed chiefly by the factor of transport. With this consideration in view, several large estates, preparing sheet rubber as the chief grade, have found it necessary to decentralise the factory work, with very satisfactory results. Outlying sections are given uniform and complete equipments of necessary buildings on a small scale, and hand-driven light machines.

Uniform coagulating tanks are installed, and the methods and quant.i.ties of chemicals employed are carefully standardised. Experience has shown that often the best sheet rubber coming to the market has been prepared on small estates; and the same applies to the product of these decentralised stations on large estates. There is no _a priori_ reason why the product from one station should differ in the smallest particular from that of another, apart from minor fluctuations which are due to variable weather conditions affecting the latex. If the contrary is found to be the case, it indicates failure on the part of the person responsible to follow the regular rules and methods.

In the natural scheme of development of a large estate, it would be necessary, of course, to have a comparatively small centrally situated factory, equipped with power and heavy machinery for working sc.r.a.p rubbers in the preparation of crepe grades below No. 1 in quality. As the yield per acre increases, or the area in bearing expands, it would be advisable later to increase the size of the central factory and buildings so as to permit of the preparation of a proportion of the crop in the form of No. 1 crepe rubber, in order to be able to comply with prevailing market demands under which preferential rates fluctuate between pale crepe and smoked sheet.

PART IV

THE FINISHED RUBBER

CHAPTER XVII

_DEFECTS IN CREPE RUBBERS_

GENERAL STYLE OF FINISH.--Broadly, there is no single and definite style of finish, but on the whole it may be stated that the greater proportion of crepe rubbers are prepared in a thin form and with a close-knit texture or finish.

Very little thick or blanket crepe is now made on estates in Malaya, so that beyond the mention of that type little need be written. A fair amount of blanket crepe is sold in the Singapore market, but it should generally be regarded as re-made rubber--_i.e._, it may have been prepared from thin crepes, or from native pale sheets, in local rubber-was.h.i.+ng factories. In appearance these crepes have a rough finish, and vary in colour according to the crude material employed.

The general preference of the market at present is for a thin, smooth-finished crepe, with a close-knitted surface--_i.e._, free from what is described as "laciness." What effect this looseness of finish can possibly have upon the quality of the rubber is not understood, but the standard type set up by the market must be comparatively free from small holes.

Under existing conditions governing the sale and purchase of rubber, various "standards" are set up. These really have no bearing upon the intrinsic qualities of the rubber, and are concerned almost entirely with superficial attributes. They are necessary in the absence of any proper scheme of evaluation for the establishment of certain standards of comparison, which imply that the rubber is apparently clean, free from certain recognised defects, and has been carefully prepared--as far as can be determined by a superficial examination. Thus the question of "finish"

has attained disproportionate importance, but must be respected when preparing rubber for sale.

Under ordinary conditions, thin crepe rubber, as it leaves the finis.h.i.+ng machines, has what may be termed "deckled" edges. On many estates, in order to comply with market conditions, the edges of the wet crepe are trimmed, and the tr.i.m.m.i.n.gs re-made into lengths of crepe. This is done under the impression that the market price is influenced by the evenness of the edges of crepe rubbers.

Again, it sometimes happens that, owing to "wear" of the rolls, the finished dry crepe may show a faint but distinct pattern of mark--a diamond or a horizontal bar. Since these are not accepted under the "standard"

comparisons, rubber exhibiting these characteristics does not obtain the top market price. In other words, these innocent and innocuous marks are regarded as defects and penalised accordingly.

Enough has been written to show how very important becomes the question of finish. It will be acknowledged that the superficial qualities demanded in the "standard" market type can be reproduced by any estate having adequate machinery and ample facilities for drying and handling the rubber.

Methods of preparation and formulae for the employment of chemicals are so well laid down that, up to the stage of machining, no difficulty need be encountered. But the standard type of finish in the dry crepes cannot be obtained unless the estate factory is fully equipped with the three types of rolls necessary--_i.e._, macerators, intermediate crepers, and smooth finis.h.i.+ng-rolls. This subject has received full discussion in Chapter XIII., and is here only mentioned with the view of emphasising the point that no estate can be blamed for a lack of "finish" in crepe rubbers if the equipment of machinery is inadequate or in poor condition.

If, on the other hand, the factory has ample machinery for requirements, and a good finish cannot be obtained on the thin crepe, then it is time the rolls were attended to and changed, or that the ratios of the driving pinions were altered.

DIRTY EDGES.--It seems to be almost impossible to keep old machines clean, and it is equally difficult to keep the edges of crepe free from oil and dirt. Usually these dark edges are to be found on crepe which is rather wide, and it will be noticed that where wide crepe is made, unless special precautions are taken, the edges of the rubber often pa.s.s under the edges of the hopper and so pick up dirt and oil. On most machines it is a great mistake to attempt the preparation of wide crepe; nothing but narrow crepe must be made. To obtain this it is necessary to decrease the width of the hopper placed above the rolls. This can easily be effected by blocks of heavy hard wood, cut to shape and fastened in position.

Sometimes the dark edges of crepe are due to another cause. Rolls may be gradually worn in the middle, so that to obtain a good finish it becomes increasingly necessary to tighten up the screws which regulate the distance between the rolls. It thus happens that just at, and beyond, the edges of the rubber the rolls grind upon each other, and fine particles of iron and graphite are transferred to the rubber. In such a case it is evident that either the rolls must be "turned" or that a new pair of rolls must be subst.i.tuted.

IRON-STAINS.--One of the causes of iron-stain on rubber has been mentioned in the preceding paragraph. This particular kind of iron-stain must not be confounded with rust-stain, and gives a dark dirty colour. It results from the grinding together of the rolls, and is usually noticed in the finis.h.i.+ng of fine pale crepe. For this operation it is necessary to screw up the rolls tightly, and it will be plain that, whenever the rolls are vacant of rubber, there is a tendency for them to grind upon each other, thus setting free fine particles of iron and graphite. In order to avoid this, one must be careful to see that between the working of each length of fine crepe the rolls should be occupied with another piece of rubber, which may be kept for the purpose. In some factories this trouble apparently does not exist, while in others the amount of wear on the rolls is surprisingly great, and the damage done to the rubber is excessive. The only way in which this difference can be accounted for is that there must be a great difference in the quality of the roll material. Some rolls seem to be excessively soft, and from these contamination by iron-stain is great. For this reason rolls are sometimes rejected, and there would appear to be an objection to any but chilled steel rolls for the final stage of finis.h.i.+ng crepe rubbers.

RUST-STAINS.--Rust-stains, on the other hand, throw the responsibility entirely upon the labour and supervision of the factory. Rust is formed upon the rolls when they are at rest, and any one pa.s.sing pale rubber between the rolls before they have been thoroughly cleaned is guilty of culpable negligence. Even when apparently clean, a piece of lower grade rubber should be pa.s.sed through the rolls several times so as to remove any slight trace of rust remaining.

Rust-stains have also been caused in a few cases by the large knives which are used to cut up lumps of coagulum, or by allowing freshly coagulated rubber to come into contact with iron vessels in the factory.

A similar appearance has been traced in a few instances to contamination of the coagulum in transit by the dust of the reddish rock (laterite) employed in localities for road-making.

OIL-MARKS.--The origin of oil-marks in crepe has already been described in Chapter XIII. The whole question resolves itself into one of cleanliness, moderation in lubrication, and supervision. The machines should be inspected every day, and once a week rolls may be swabbed down with a 10 per cent. solution of caustic soda applied by means of a piece of cloth fastened round the end of a stick. Immediately after this operation water should be turned on and the rolls set in motion, so that all traces of caustic soda are thoroughly removed. If possible, lubrication by oil should be subst.i.tuted by grease lubrication through screw caps.

Particular attention should be paid to the back of the machines. None but the individual in charge of engines should be allowed to lubricate the machines, and he should be held responsible for any excess of lubricant.

As a rule oil-marks are restricted to the edges or the proximity of the edges of crepe, but sometimes the streak is to be found in the middle of the length. In such a case it is almost certain that the oil or grease has been picked up by the rubber in the tray. It sometimes happens, if the "liners" of the bearings are eccentrically worn, that a few drops of dirty oil or a particle of grease are squirted out to some distance. These usually find a resting-place in the tray, and the contamination may then appear in any part of the rubber.

It will be clear, therefore, that all trays beneath machines should be examined as the probable source of danger from contamination by oil and dirt. If the trays are as wide as or wider than the effective portion of the rolls, they should be discarded. In their place (except sometimes in the case of the macerating machine) all that is necessary is a movable piece of board, in width not less than from 4 to 6 inches shorter than the width of the rolls. Any oil or grease ejected from the bearings will thus be allowed to fall clear of the board; and defects due to oil streaks, etc., will be very much diminished, if not entirely obviated.

This point in connection with the damage possible by the existence of wide trays is commended to the notice of manufacturers of machines for plantations, as it is common to find that trays are made which contravene the rule prescribed by experience. In fact, trays on some machines have been so designed as to act as "traps" for all dirty matter exuding from the bearings. Not only so; they are sometimes made of such a shape and height that oil or grease lodging upon the edges act as a "wipe" to the rolls, thus increasing the possibility of contamination. Until this defect was investigated, it was common to note continued contamination of pale crepes in spite of all precautions taken in cleaning the rolls at frequent intervals. The trouble due to this cause is intensified when the same machines are employed for the preparation of sc.r.a.p-rubber crepes and No. 1 crepe. Small pieces of sc.r.a.p find their way towards the bearings and lodge on the edges of the trays. Unless a thorough inspection is made before proceeding with the working of the No. 1 (pale) grade, contamination may be continuous.

DIRT.--Streaks due to the presence of dirt (as apart from oil or grease contamination, or that due to pieces of oxidised sc.r.a.p) are unusual, and when they do appear their origin seems to be somewhat of a mystery. It could scarcely be advanced that the dirt was picked up on the machines, as it is difficult to imagine where such dirt could come from. In one or two instances there has been fairly clear evidence that the dirt was contained in the coagulum, and the only explanation fitting the case is that it fell into the latex after straining and during the course of coagulation. On cutting open lumps of coagulum brought in from the field division, it has sometimes been noticed that dirt is included, and the foregoing explanation is the only reasonable one. How it was possible for dirt to get into the latex must be left for explanation to those better acquainted with the conditions under which the latex was coagulated.

HOLES.--On some estates it would seem impossible, with the existing machines, to make really good crepe. The complaint is that, if thin crepe is attempted, it is invariably found to be "full of holes"; and as, apparently, the presence or absence of small holes in crepe rubber is a factor which influences buyers, this defect must be avoided at all costs.

Why this matter of small holes in thin crepe should weigh so heavily with buyers is a matter which the writers are not in a position to explain. As a matter of fact, the presence of small holes is most generally an indication that the rubber has received the minimum amount of working on the rolls consistent with good was.h.i.+ng. Further working would only be undertaken with the idea of so consolidating the rubber as to get rid of holes in order to meet the market scheme of valuation.