The Preparation of Plantation Rubber Part 21

The removal of "stops" at the lower end enables the foremost frame to be removed, and the succeeding frames slide into a new position. Thus the freshly prepared sheets, entering at the higher end, gradually and automatically move towards the furnace as the frames of dry rubber are removed from the lower end.

[Ill.u.s.tration: THE NEW "BARKER" TYPE OF SMOKE-HOUSE: A SMALL UNIT.

The racks slide automatically from top to bottom on withdrawal of the lower frames through door at front. The furnace is contained in the brick compartment at the lower (front) end.]

Thus far only small units have been seen. It is claimed that, properly prepared, sheet rubber can be smoke-cured in about five or six days, and it is stated that installations have been in successful working for sufficiently long periods to prove their efficacy. The device is better known in Java and Sumatra than in Malaya. The capacity of a unit building is stated to be 7,000 lbs. per month, calculating on a six days' cycle of working. In a more recent design provision is made at the lower end for a water tank, into which all rubber can be discharged in case of fire.

CHAPTER XVI

_OTHER BUILDINGS (continued) AND SITUATION OF BUILDINGS_

SORTING-ROOM AND PACKING-ROOM.--It is in these departments that most factory installations are lacking. More often than one cares to acknowledge, sorting and packing are done under conditions which place a premium upon poor work. As a consequence, consignments of rubber are often marred by the inclusion of defective specimens. The result is that s.h.i.+pments may be rejected when tendered against contracts, or that allowances in price have to be made. In many instances it would not be fair to lay the blame upon the manager or an a.s.sistant, as it is obviously impossible for an individual to inspect every piece of rubber. Neither would it be strictly fair in some cases to ascribe the fault to pure carelessness on the part of the coolies.

Often the only provision made for this important work is the lower room of a drying-shed, which may also contain hanging rubber. Under these circ.u.mstances, s.p.a.ce is cramped, and the light often poor. Small defects may pa.s.s unnoticed, and the general surroundings do not conduce to keen work.

Where, for economic reasons, the sorting and packing operations are conducted in the drying-shed, there should be ample s.p.a.ce free from hanging rubber, and it should not be possible for wet rubber placed in the upper room to drip upon the dry rubber below or upon packed cases. There should be plenty of light, and for this reason windows should be ample. Usually the window-frames are fitted with wooden shutters, which are preferably hung on horizontal hinges from the top of the frame. By this device it is not necessary to close all windows during a shower of rain, and rubber may be stacked near a window with reasonable chance that direct sunlight will not be allowed to fall upon it.

In dealing with smoked sheet, it is advised that the rubber to be examined should be placed upon tables facing the windows, so that each piece may be scrutinised in a strong light.

Crepe rubber also is best examined in a strong light, but preferably with one's back towards the source of light or at an angle to it. For this work coolies usually are most efficient when sitting on the floor.

It will be clear from the foregoing remarks that the best conditions would be secured in a separate building especially constructed. A single room would be all that is required; at one end sorting could be undertaken, while packing could be done at the other end. No hanging rubber should be allowed in the room.

The floor should be of hard timber, and raised from the ground, to the height approximately of a bullock-cart or motor-lorry, as the case may be.

The boxes of rubber could thus be transported by small hand-trucks on a level with the transport vehicle, reducing labour to the minimum.

The ventilation of the building should be good, especially if cases of rubber are to be stored therein; and the entire structure should be weather-proof.

STORE-ROOMS FOR RUBBER AND STORAGE.--The question of storage of rubber in factory buildings has always possessed importance, but has demanded increased consideration recently.

From experience in this country, it is clear that cement floors for store-rooms or packing-sheds are the least suitable. They are often visibly damp, especially in the early morning. To allow rubber, packed or unpacked, to remain upon a cement floor in the tropics, is to court trouble from moulds, external or internal. If the employment of a cement floor is unavoidable, the rubber and boxes should be raised on wooden supports, giving a clearance of at least 3 or 4 inches, and there should be clear ventilation s.p.a.ce between tiers of boxes.

Experience indicates that the best type of floor is that already advised for sorting and packing rooms--_i.e._, a good hard timber floor raised at least 3 feet above ground-level. Apart from the advantage in labour specified in the previous paragraphs, this provision of ample ventilation s.p.a.ce below the floor is a great consideration in the preservation of the timber. Raised store-rooms become essential in low-lying districts which are at all subject to flooding, yet the writer has seen many boxes of rubber damaged by flood-water entering a packing-room situated on the level.

The question has often been raised recently as to the length of the period during which rubber may be safely stored in this country. The answer can be only supplied by experience, of which up to the present we have none possible of being cla.s.sed as reliable. Whatever storage may have been done in the past has been influenced greatly by the unsuitability of the storage accommodation, and the fact that often the rubber was not prepared with a view to prolonged storage.

While the market demand was strong, rubber was being s.h.i.+pped and pa.s.sed into circulation, at a rate which did not demand investigation of the subject of local storage. In the year 1918 conditions were such as to bring the matter into prominence, and we were able to tender advice on the lines given in this chapter. The necessity pa.s.sed, but has again arisen.

Our experience goes to prove that if rubber is properly prepared and thoroughly dried before packing, it will remain in good condition for a period of a year or more in this country. How much beyond a year it may be kept remains to be determined. The a.s.sumption of "proper preparation"

leaves great room for reservations.

In the case of crepe rubbers, there is no great difficulty, provided that the recognised methods and formulae are employed, and that the rubber is packed only when perfectly dry. Under those conditions, the higher grades of crepe remain apparently unaffected on storing. Any appreciable deterioration may be attributed to defective preparation or external causes, such as accidental damage by water.

The prolonged storage of lower grade rubbers is attended by more risk, especially in the case of the lowest grade (earth-sc.r.a.p) from estates which neglect the practice of regular and frequent collection of the raw product.

The same reservation applies to crepes made from tree-sc.r.a.p which is not collected daily. In these types of crepe rubber "tackiness" may be initially present only in small degree, but the final damage may be immensely greater by close contact of the folded rubber during prolonged storage.

When we come to discuss the possibility of storage of smoked sheets, the difficulties become immensely greater. We have yet no reliable experience as to the keeping properties of this grade when properly prepared, fully cured, correctly packed, and stored under the best of local conditions. It is understood, of course, that in the qualification by the term "local"

conditions, we a.s.sume it to be more difficult to store rubber generally in Malaya than in a temperate climate. The average temperature and humidity of the atmosphere are here much more favourable to the development of mould growths than would be the case, say, in Great Britain.

In discussing this question, as far as it refers to the preservation by storing of smoked sheet rubber, it is not fair to draw conclusions as to the likely behaviour of packed rubber from data based upon observation of loose specimens. We have samples of smoked sheets prepared in 1910, and these, superficially, appear to have remained unchanged. No mould is present and, as far as intermittent observation enables us to judge, moulds have never been incident. Whether such rubber would have been preserved in this condition had it formed part of a packed case, is a point upon which we have no experience; neither can we give any opinion. It seems true, however, that loose specimens "keep" better than bulk samples of the same preparation.

It cannot be argued that the present good condition of these old specimens may be due to correct preparation. In those days methods and formulae were rather haphazard, especially in view of the fact that the daily variability of dry rubber content of latices was not then recognised.

One would rather submit the factor of adequate smoke-curing as the chief influence in the superficial preservation of smoked sheets. Ten or eleven years ago it was considered advisable to allow the rubber to remain in the smoke-house for a period extending well beyond that necessary for ordinary drying. As a result, very dark rubber was produced, which was thoroughly impregnated with the products of wood combustion. There would seem to be little doubt that this procedure was responsible for the prolonged freedom from mould growths.

Market standards have varied to some degree since, with a tendency to prefer a paler product than that in vogue, say, six or seven years ago.

Moreover, standardised methods of preparation have been introduced, with the result that sheets of a desirably high standard can be produced in from ten to fourteen days, when smoke-curing is conducted only during night hours. Some estates are equipped with smoke-houses which, by continuity of working day and night, provide smoke-dried rubber in from five to six days; but the actual hours of smoke-curing are approximately equal to those of the ordinary type of house.

This tendency towards the production of sheets paler in colour than the old standard is probably largely responsible in the present for the commonly observed incidence of surface moulds on stored smoked sheets, and also for some complaints of "under-curing," where the term specifically refers to a failure to dry and cure the rubber thoroughly. Boxes of smoked sheets, which had been stored for varying periods up to five months, were recently inspected, and, in the majority of instances, surface moulds were found to be plentiful. In all cases it was observed that the trouble was intensified where boxes of rubber were stored in contact with cement floors.

This "under-curing" is not a question solely of the duration of smoke-drying, although probably the modern practice of curtailing the period has exerted a great influence. To make this clear, it may be stated that, given two batches of uniformly prepared wet sheets, it would be possible to smoke-cure them for equal periods in different houses, so as to produce one batch very much paler in colour than the other, although the total hours of actual smoke-curing would be identical. In order to produce such effects, all that is necessary is to employ different timbers for fuel or different types of furnaces. In the one case there would be produced heat and very little smoke, while in the other the necessary heat would be obtained plus plenty of smoke. The best results naturally are obtained by the employment of the happy medium, and if smoked sheets have to be stored, the ordinary period of smoke-curing should be prolonged to an interval consistent with the capacity of the smoke-house.

All precautions taken in preparation and curing can be nullified, as already indicated, by unsuitable storage conditions.

TOOL-SHEDS AND STORE-ROOMS.--In some factories it is the rule to see lime, cement, spare rolls, sieves, and a general heterogeneous a.s.sortment occupying part of the rubber-drying rooms. The inconvenience is often great; and it certainly seems that these stores and tools are of sufficient value to be accommodated in suitable buildings.

SITUATION OF FACTORY BUILDINGS.--There can be no doubt that a great deal of the "spot" disease trouble, and the general slowness of drying, can be attributed in many factories to the unsuitability of the site chosen.

Probably the idea which actuated those responsible for the choice of site generally was proximity to a water supply. This would account for the fact that a number of factories are situated in valleys or near swamps. More often than not, also, the actual clear s.p.a.ce is very limited, and rubber trees grow close up to the walls of the buildings. Under such circ.u.mstances, it is difficult to see how these buildings can be anything but dark and damp, and it is not difficult to understand the slow rate of drying. In a few cases the sites chosen proved to be so unsuitable that the estates were confronted with a very serious problem, the solution to which was, either the erection of another complete set of buildings in a more suitable spot or the installation of artificial driers.

It must be laid down as an axiom that the first essential in a suitable site is that water may be brought to it easily, but, as already indicated, this does not mean that the buildings need be placed in actual proximity to the water-supply. The mistakes made by pioneers in this work are not likely to be repeated, and it is common now to note well-designed and comprehensive schemes in which the water is pumped to a reservoir placed at a suitable elevation, whence the supply is gravitated to bungalows, coolie lines, and the factory. The importance of securing a plentiful supply of good water for factory purposes cannot be exaggerated, and it is a point which is only thoroughly appreciated on estates where smoke-sheet rubber has to be prepared.

The second essential, but of equal importance, is that there shall be an ample open s.p.a.ce on which the sun may s.h.i.+ne all day. There must be no trees too near the buildings, and there should be no adjacent swamps. Preferably, the site should be on a raised position, so that it will be impossible for surrounding trees to cut off suns.h.i.+ne, even when they are fully grown. From such an arrangement it will follow that the factory will be light and airy, and the drying-houses will receive the maximum of benefit to drying from direct suns.h.i.+ne on the roof and walls. There can be little doubt that these considerations play a most important part in determining the rate of drying of the rubber, and where comparisons are made between the rates of drying in various drying-houses all these factors enter into the question and contribute to the total result. Presuming that the thin crepes made in two factories are equal in thickness, it is not uncommon to find that in a drying-house, situated in a wide open s.p.a.ce, the period of drying may be as low as six or seven days; while in another drying-house, situated near a swamp and surrounded by trees, the period may be as high as eighteen days to twenty-one days. The figures quoted are not fict.i.tious, but are facts actually noted in the course of the writers' experience.

A great deal also depends upon the exact position of buildings. Thus, to obtain the maximum of light in a factory, it will be obviously beneficial to erect it with the long sides running east and west, so that the windows face the north and south, and the large end doors face the east and west respectively. At first sight it would appear that the best position for the machines would be on the north side of the building where no sun can enter; but a moment's consideration shows that the south side would give the best results. By the time the sun has come round to the south, it is usually high in the heavens, and the direct suns.h.i.+ne does not fall very far into the room. Even should it play upon the machines for an hour or two during the day, no harm could result to the rubber which was being worked, as no piece would remain there a sufficiently long time to be injured in the slightest degree. Placed in this position, the maximum benefit of light would be obtained, whereas if the length of the building ran east and west, the machines would have only either the morning or afternoon light.

[Ill.u.s.tration: SUGGESTED ARRANGEMENT OF BUILDING.]

While it is advisable to erect a factory running east and west, the drying-houses should run north and south. In this position the maximum wall area will be exposed to the sun during the day, and it will be possible to manipulate the windows of the drying-rooms so that those along one side are open, and it will never be necessary to close all the windows at any time of the day. Thus the windows facing east will be closed, and those facing west will be open until after midday; then _vice versa_. With such an arrangement a more uniform temperature may be obtained than by any other arrangement of the buildings. If the building ran east and west, the windows on the north side could remain open all day, while those facing south would have to remain closed practically all day. The south side of the house would be heated by the sun, while the north side would remain cool, and the rates of drying would be correspondingly unequal. The total wall area heated by the sun at any time of the day would be less in this position than if the house ran north and south.

Similarly, to obtain the best drying effect during the daytime in a smoke-house the building should run north and south. By this means the temperature will be maintained to the maximum possible by sun heat, and the rate of drying will correspond.

_References to Sketch Plan._

Drying-house No. 2 should be of two storeys, and unless a separate sorting and packing room is to be built, No. 1 should also have two floors (see previous notes on packing-rooms).

In the factory--

_V_ shows the position of the verandah, which may be quite open and only divided from the inner room by

_S_, a wall composed of very strong expanded metal, which allows light and air to enter the factory.

_T,T_ are the glazed tile tanks for the reception of latex, sc.r.a.p rubbers, and bark-shavings.

_M_ shows the position of the machines on the south side of the factory, with the direction of extensions, and