No. 2 (192I) REMARKS ON CANNING 43 



Opened with a tin opener, or ' key opening ' and is then provided 

 with a wire ' key,' which rolls up the whole cover leaving the 

 contents fully exposed. This class of tin is greatly preferable to 

 the keyless since the top is necessarily obvious, so that the contents, 

 e.g., sardines, are properly exposed on opening the cans, the 

 consumer opens the tin readily without cutting his fingers or 

 leaving a jagged edge, the fish are not torn by the tin opener and 

 are therefore better in appearance, and the clean tin dish is more 

 convenient for subsequent domestic use than the jagged one left 

 by the tin opener. But they are necessarily slightly dearer. The 

 Government Cannery does not at present make ' key openers ' 

 though the solderless plant is adapted for them. 



The oval tins are also made as key-openers, but cylindrical are 

 mostly keyless except the small paste tins known as ' strip off ' ; 

 these are opened with a key which tears off a narrow strip at the 

 top of the can, the strip following a groove in the tin plate ; this 

 leaves the contents visible and untouched. 



19. The ordinary cylindrical keyless can is made either with 

 the full opening or capped. The first named is a cylinder fully 

 open at the top and closed when packed usually by a cylindrical 

 top fitting inside the tin and soldered, or with a flanged top seamed 

 to the body with a wash of solder externally. These are conve- 

 nient for filling since the full width of the can is available. 

 Capped tins are those which are sent out from the can-making 

 factory with the top in place but which have an orifice of varying 

 size, usually about % of the full diameter, through which the 

 contents are packed ; the orifice is then closed by a cap of tin 

 plate which fits neatly into a groove provided on the top and is 

 then readily soldered hermetically. This is convenient to the 

 canner since the caps are easily and readily sealed, but are not so 

 convenient to fill or empty, especially when the contents are paste. 

 Lever-top tins are those which, like capped tins, have a central 

 tubular orifice into which a dished cover is inserted and forced 

 closely down ; these however cannot be closed hermetically unless 

 externally soldered in which case these tins lose their special 

 value, viz., that they can be opened with a lever, such as a stout 

 coin. Hence they cannot be used for putrescible goods, though 

 suitable for goods like jams which are poured boiling hot into the 

 cans, when the groove which surrounds the orifice into which the 

 cover is inserted, may be filled with melted paraffin wax, dammar, 



