372 



The Supplement to the Tropical Agriculturist 



SMOKING OF RUBBER. 



DUTCH EXPERT'S OPINIONS ON THE 

 METHODS ADOPTED. 



The smoking of rubber quite recently came 

 up for discussion at a congress of rubber plan- 

 ters held at Bandoeng (Java). During the de- 

 bate it was clear that nobody had much experi- 

 ence about the matter, and it might, therefore, 

 be of interest to hear what Dr. K Goeter writes. 

 The following is taken from the Sumatra Post : 



As is well-known, says the doctor, Para 

 rubber ie obtained in a different way to planta- 

 tion rubber. Th6n follows a description of the 

 method adopted in Brazil for the preparation of 

 rubber. The writer proceeds : It is, however, 

 most noticeable, and according to the experi- 

 ences of Trillat and other investigators, that 

 wood smoke contains another substance (besides 

 creosote) having strong conserving properties, 

 namely, formaldehyde which dissolved in water 

 is the formaline or formol of commerce. It was, 

 therefore, thought probable that this stuff would 

 be found in small quantities in smoked rubber. 

 This was indeed found to be so. With the help 

 of various sensitive reactions, I could undoubt- 

 edly show the presence of formaldehyde in 

 smoked rubber sheets, so that by reason of this 

 result it may be taken that the conserving work 

 of smoke on rubber must at least be partly 

 attributed to the presence of formaldehyde in 

 the smoke. In the development of smoke it 

 would be well to bear this in mind, by endeav- 

 ouring to get a smoke that is as rich as possible 

 in formaldehyde. 



Quality or the Smoke. 



Now it has been found that organic sub- 

 stances, for instance, sugar, will through in- 

 complete combustion, produce more formal- 

 dehyde, when they are placed in contact with a 

 metal, such as iron, will give a smoke with a 

 higher percentage of formaldehyde than when 

 that contact with a metal does not exist. This 

 seems to me important enough to revert to the 

 subject again by and by. First I shall parti- 

 cularly direct attention to the fact that smoke 

 is caused by incomplete combustion, in other 

 words by a limited supply of air. On this point 

 it has appeared to me that, in practice, the air 

 is not sufficiently impeded. The wood must 

 smoulder, therefore it must burn without flame 

 and this is only attained by limiting the admis- 

 sion of air. If there is too much air, less smoke 

 is obtained and more fuel is used up ; so that 

 it is less economical from two points of view. 

 It was tried to remedy this by making the fuel 

 wet, but this was a wrong procedure because 

 it brought more vapour (aqueous) into the 

 smoking room. As a result of that the rubber 

 took necessarily a longer time to dry. Besides 

 under these circumstances, more tarry pro- 

 ducts were developed through which one ran 

 the risk of getting a foul tarry deposit form- 

 ing on the rubber that would spoil the 

 outward appearance and so the quality of tho 

 rubber. Finally, it might be well also for plan- 

 ters to bear in mind that in smoke, a poisonous 

 gas, the well-known carbonic oxide is formed, 

 of which the relative quantity increases under 

 the last-rjamed conditions. From a hygienic 



point of view the health of the coolies working 

 continually in an atmosphere of smoke should 

 be considered. Yet for a uniform smoking it 

 cannot be avoided that the hanging sheets of 

 rubber have to be regularly turned about. In 

 any case proper ventilation should be seen to 

 by having the windows wide open. 



Mk. Ridley's House. 



Whether smoking has a direct influence on 

 the physical properties, for instance, on the 

 elasticity of the product, I should not dare at 

 present to decide. As a fact, it can only be 

 said now that smoked rubber keeps better 

 and is not so liable to mould as unsmoked 

 rubber. As a rule a higher price is paid for 

 smoked rubber on this account. As to how 

 smoking should be done, opinions differ. Mr 

 Ridley, Director of the Botanical Gardens in 

 Singapore, gives his experiences on this point 

 in the Agricultural Bulletin of tho Straits 

 from which I take the following (here follows 

 a description of Mr Ridley's process, noting 

 in particular that he used a wooden house with 

 an attap roof.) Then the doctor continues : — 



The vapour and the tarry substances of the 

 smoke are practically fully absorbed by the 

 woodwook and the attap, so that the rubber 

 is not covered with a foul damp substance. 

 Compared with this, the experiences of others 

 using a stone house with a galvanized iron 

 roof and into which the smoke is led from with- 

 out, were less favourable. In this case there 

 was a deposit of tarry substances on the floor 

 and eVery part of the building and even on the 

 rubber. This trouble does not occur in a 

 wooden house; although the woodwork becomes 

 dark-brown and even black by the precipita- 

 tions from the smoke, the rubber remains dry 

 under these circumstances and of good colour. 

 No other ventilation than through the crevices 

 is necessary. Only when men have to go into 

 the smoking room care should be taken to 

 throw the windows open. Generally the door 

 is left open but as this is at the lowest end of 

 the building, the draught drives the smoke 

 through the rubber to the higher end of the 

 building. Coconut husks may be used as fuel 

 instead of wood, but coconut husk and also saw- 

 dust produce sparks which fly up and deposit 

 themselves on the rubber as bits of wood 

 charcoal. Experiment for improving the smo- 

 king process by the addition of creosote had not 

 the desired favourable result. The writer con- 

 cludes his article with a word of praise for Mr. 

 Ridley's wooden house. 



SISAL CULTIVATION IN FIJI. 



Captain D Calder's sisal plantation at Vesari 

 is at present looking remarkably well, a good 

 proportion of tho plants having arrived at the 

 mature stage at which the leaves are milled. The 

 necessary machinery has been imported, and it 

 will not be long until the mill is in running order. 

 Apparently it will not be long ere a shipment of 

 fibre will be made, thus establishing a new in- 

 dustry in Fiji. The Government is offering a 

 bonus of £5C0 for the first ten tons grown and 

 exported, and it looks as though Captain Calder 

 will enjoy the distinction of drawing the bonus. 

 — Times, Aug. 31, 



