No. 2 (1921) REMARKS ON CANNING lOI 



processes. Briefly it is primarily a matter of good sealing 

 whether by solder or by double seaming, and of good testing and 

 exhausting, with, if pressure steam is used in processing, additional 

 precautions to prevent undue strain on the joints, especially those 

 made by soldering. 



136. Defects from mere distortions ) 'springers.' — As shown above 

 {s.v. ' exhausting ' and ' processing ') cans are often liable to slight 

 and occasionally to serious distortion from mechanical (air and 

 steam pressure) causes. When the tin is very thin and unsuitable 

 to the character of the cans — as happened frequently during the 

 war when tin plate was almost unprocurable and unsuitable quali- 

 ties had to be used — this defect was very common ; many of the 

 plates were found buckled even when in the flat, and this itself 

 gave rise to buckled tops and bottoms ; or the thin plate of cans 

 processed under high temperature and pressure, buckled severely 

 under the pressure and became permanently distorted ; or the 

 exhaustion was too complete and the thin plate buckled by reason 

 of the high internal vacuum. These distortions are purely 

 mechanical and have nothing to do with the condition of the 

 contents ; but owing to the possibility of their rejection by the 

 consumer who mistakes these ' springers ' for ' swells, ' it is 

 necessary to avoid them by using plate suitable to the sizes and 

 shapes of the cans, and not to issue, even at the cost of some loss, 

 such 'springers' as are reasonably liable to be mistaken for 

 ' swells '. 



137. Another and frequent source of springers is imperfect or 

 imperfectly set dies, or uneven pressure or imperfect bufl"ers in the 

 presses which cut the tops and bottoms ; this of course is more 

 frequent in dies of large superficial area, which require most 

 careful setting, otherwise the tops and bottoms will be so distorted, 

 usually at corners diagonally opposite, that they will not lie flat 

 on a flat surface. This distortion is a ready cause of springers ; 

 when the can is put together and forcibly secured in position by 

 the solderer with his ratiere, the soldered, distorted plate at once 

 strives to reassume a distorted condition ; hence a tendency to 

 buckling which may be immediate or developed under subsequent 

 pressure ; in any case the attempt to resume its distorted form 

 causes a heavy strain on the joints and, especially in the case of 

 soldered tins, is a fruitful cause of leaks. Hence much attention 

 is required to plate and to machines. 



5-A 



