[22] "The Cause of Rustiness in Sheet-Rubber," H. J. Hellendoorn, Archief voor de Rubbercultuur, October, 1919 (Communication from the Central Rubber Station, Buitenzorg, Java). Without going into a full discussion of the subject, the following points noted in the experimental work may be quoted: 1. Rustiness could apparently be produced at any time merely by keeping freshly rolled sheets for periods varying from twenty-four to forty-eight hours in a moist atmosphere. 2. Sheets placed immediately in a temperature of, say, 110° to 130° F. never showed "rust"; but if air-dried at ordinary room temperature, "rust" might appear. 3. "Rust" can be prevented by soaking freshly prepared sheets in dilute solutions of disinfectants--_e.g._, formalin, sodium bisulphite, or chinosol. If subsequently the sheets are hung for any length of time in a moist atmosphere, the protective effect of the disinfectant gradually vanishes and "rustiness" may be produced. The same disinfecting effect may be obtained by the use of steam or hot water. It was found that there was less liability to the formation of "rust" when sheets were immersed in water at a temperature of 95° to 120° F., whilst steeping at 140° F. gave complete freedom. 4. It was shown that the micro-organisms which cause decomposition of the serum-products flourish only in the presence of air--_i.e._, they are aerobic in character. It is not uncommon to find, therefore, that "rust" may be incident only on those parts of a sheet which have been exposed for some time to air and moisture before being placed in a warm smoke-room. 5. The optimal temperature for development of the particular organisms appeared to be about 100° F., in a moist atmosphere. 6. Soaking the sheets in water (except the short immersion in hot water, which we recommend), even for a period extending over a week, does not hinder the formation of "rust." 7. Rustiness may be prevented by placing the sheets in a sufficiently warmed smoke-house as long as there is adequate ventilation and a moist atmosphere does not persist. The simplest means of prevention is to soak the sheets first for a short period in water, and then to hang them to drip for a few hours in a well-ventilated place, outside the factory and under cover.[23] [23] We advise and practise hanging sheets in the open, without shade or cover. It will be gathered that, although there may be a slight difference between our previous views and those advanced by Hellendoorn as to the exact cause of formation of the "rusty" film, the general conclusions are identical with those given by us in preceding paragraphs and previously advised in the Malayan reports of the Rubber Growers' Association.