102 MADRAS FISHERIES BULLETIN VOL- XIII, 



138. A 'swell' is quite unmistakable; since it is caused by 

 internal decomposition with the production of large quantities of gas, 

 the whole can swells by the severe internal pressure so that both 

 top and bottom become convex and cannot be pressed inward by any 

 ordinary pressure ; they will often burst rather than yield to external 

 pressure ; in many cans the seams, especially if soldered, give way 

 slightly so that the contents ooze out. If such cans are opened 

 there is a strong escape of foul-smelling gas, and the contents 

 are seen to be mushy and unmistakably tainted. 



But the ' springer ' or ' flipper ' shows no such conditions ; 

 in nearly every case it is only one side (top or bottom) that shows 

 any convexity ; this convexity is, moreover, often only partial, 

 extending over part of the affected plate, and is generally compara- 

 tively slight. This fact of itself shows that the convexity is not 

 due to internal gas pressure, for in such case (internal gas pressure) 

 the convexity must necessarily show itself on both plates equally 

 since the gas pressure is necessarily equal over the whole area of 

 the can ; moreover gas pressure could not render part of one side 

 convex and leave the other part normal. Finally, these ' springers ' 

 can readily be pressed inward by the mere pressure of a finger, 

 and may or may not resume their apparent convexity ; this is 

 conclusive of the fact that the contents have not decomposed but 

 are perfectly sound. This is well known to canners and has been 

 tested in very numerous cases in the Government Cannery and 

 the contents personally tasted and consumed. 



139. Hence it is unfair to canneries that 'springers' should 

 be treated as though ' swells '. Nevertheless the wise canner will 



(1) take every precaution to prevent these springers by the use 

 of suitable and good plate, by careful stamping of the tops 

 and bottoms in a properly adjusted press, by proper exhaustion 

 and processing, and by care in releasing processed cans from 

 pressure ; 



(2) he will refuse to issue any cans which are so markedly 

 distorted that the public are likely to mistake springers for swells 

 and thus cause the canner loss of reputation and consequently of 

 custom. 



140. Originally bad contents.— This has been dealt with above. 

 No canner who regards the consumer or himself will be other than 

 absolutely careful in selecting and using perfectly sound canning 

 material ; he will suffer any loss rather than pack, for instance, 



