No. 2 (1921) REMARKS ON CANNiySS/^O^ ''^^A^-r^ ^^ 



CHAPTER II. \^- 

 Containers. 



9, It is clear then that the provision of containers which can be 



hermetically sealed is the sine qua non of canning. The invention 



of the tin plate can w^as the starting point of the industry as 



distinguished from the discovery of canning; no other material 



lends itself so cheaply and conveniently as tin plate notw^ithstand- 



ing certain disadvantages arising from its metallic character ; 



glass jars or bottles though largely and increasingly in use, and 



preferable both hygienically as free from acting and being acted 



upon by the contents, and commercially as displaying the contents 



attractively especially in the case of fruits, are rather more 



difficult to seal hermetically and are very liable to fracture both in 



the process of canning and in transport ; they are also heavier and 



more expensive; stoneware jars or bottles are heavy and do not 



display the contents, while wood and paper (pasteboard) containers 



are useless for absolutely hermetical sealing as required for fish, 



being porous and liable to shrinkage, etc. The chief disadvantages 



of the tin container are — 



(1) its liability to act and be acted upon by its contents, 

 especially if they are shell fish or acid fruits ; 



(2) their liability to rust ; 



(3) the invisibility of their contents. 



But the advantages of lightness, strength, ease of hermetical 

 sealing, cheapness, suitability for packing and transport, render 

 the tin can the favourite class of container, and, as an abbreviation 

 of the original word 'canister," it has now given its name (cans 

 and canning) to all classes of containers even when of glass. The 

 containers generally dealt with in this bulletin are cans of tin plate 

 being those most in use for fish canning. 

 10. The cans mostly used are — 



{a) the ordinary rectangular tins of various sizes as used for 

 sardines ; 



{h) oval tins ; 



(r) cylindrical, which may be flats of diameter comparatively 

 wide as compared with height such as butter tins, or tails which 

 are cylindrical cans of heights equal to or greater than the diameter, 

 such as those used for American salmon, soups, jams, vegetables, etc. 



