96 MADRAS FISHERIES BULLETIN VOL. XIII, 



Open baths of some solution such as calcium chloride or of oil 

 which can be heated much above 212° F. without boiling ; hence 

 cans placed in such baths can be raised above 212° F. without 

 steam plant. This plan is very easy and successful for cans such 

 as sardines in oil, for in such cans there is, ex-hypothesi, little or 

 no air and very little moisture, the cans being fully filled with 

 fried fish and oil Consequently, however, high the temperature of 

 the bath there is no internal pressure within the cans nor, being 

 boiled in an open pan, is there any external pressure. Hence this 

 process is quite safe for cans full of fish in oil. It may be otherwise 

 where soldered cans have considerable internal air spaces and a 

 certain amount of fluid or moist contents; for in such bath it is 

 obvious that any internal pressure due to expanded air or to the 

 formation of steam within the cans is exerted to the full and 

 throughout the operation without any counterbalancing pressure 

 from external steam ; hence the strain on the joints is continuous 

 and may frequently result in leaks and distortions of tops and 

 bottoms, and may even burst the seams. The danger of scalding 

 may of course be minimised by properly covering the cans and 

 pan with heavy wooden or other covers, but this does not remove 

 the possibility of leaks, etc. The process was at first in favour, and 

 then grew into disfavour ; it is said to be now reasserting itself, 

 possibly because soldering is giving way to mechanical closing by 

 locked seams. The calcium chloride solution or oil will give any 

 necessary temperature ; oil has the disadvantage of expense and of 

 giving off fumes, especially if heated by open fire, but has the 

 advantage of not evaporating ; chloride of calcium is very cheap 

 and fumeless but the water rapidly evaporates and has to be 

 constantly supplied ; hence a tendency for the bath to rise unduly 

 in temperature with the density of the solution and consequently 

 to over-heat the cans unless carefully watched and corrected, e.g.. 

 by a small continuous addition of water, supplied automatically at 

 a given rate from a supply vessel. It is said that slight discoloura- 

 tion of the tins is caused by calcium chloride; experiments at 

 Beypore do not show any such appreciable result ; oil, of course, 

 does not discolour the cans. The advantages of these high 

 temperature open baths are considerable where steam is not 

 available. 



127. It is well to spread out the processed cans on the floor 

 immediately after removal from the kettle and douche them with 



