Contributory factors in the store are:
(1) Lack of cleanliness of utensils, particularly of coagulating dishes or tanks.
The trouble becomes acute sometimes where wooden tanks are employed. Unless the tank and the partitions are thoroughly and regularly cleansed, the wood may become coated with a bacterial slime, which is capable of causing what may be termed “fermentation” of the latex layers in contact.
The tank should be thoroughly cleaned occasionally with a weak (5 per cent.) solution of sodium bisulphite. The partitions should be scrubbed and placed in the sun twice or three times a week.
(2) Allowing latex to stand too long before treatment. This point needs no further expansion.
(3) The use of a latex of too high a rubber content. Such latices are difficult to handle in order to secure uniform mixture with the coagulant.
(4) The use of too concentrated a solution of coagulant. In conjunction with (3) there may be a rapid and irregular coagulation, giving rise not only to decomposition in parts (and subsequent formation of gas), but also to the formation of true “air-bubbles” by inclusion of air during stirring.
(5) The use of insufficient coagulant. Coagulation is slow and incomplete.
(6) Defective straining and skimming. Small flocculated particles of rubber may pass, or be rubbed through, the strainer. If allowed to remain, they act as local points of danger.
(7) The proximity of the coagulating latex to some source of heat, or exposure to sunlight.