24 THE CANNING OF FOODS. 



CONTAINERS. 



The first container used was the ordinary glass bottle with a com- 

 paratively small mouth, and was closed with a cork. The next step 

 was the use of a resinous wax to cover the cork. The bottle was 

 modified to the more convenient or jar form, and a groove run around 

 the top so that a tin cap might be sealed in place with wax. This 

 method of sealing was common in domestic canning until about 1890. 

 The metal screw cap with the rubber ring and various other devices, 

 most of which depend on a rubber or fiber joint to exclude the air, 

 have been introduced since that date. The glass jar is largely used 

 in domestic canning, but not commercially, as it is heavy, breaks 

 easily, can not be handled by automatic machinery, will not stand 

 hard processing without special precautions, and increases freight 

 rates. Glass containers are used for preserves, spiced and pickled 

 fruits, and for the limited canning for which the consumers are 

 willing to pay a fancy price. Very recently improvements have been 

 made in glass jars and the methods of sealing, which may extend their 

 usefulness, especially to such products as can not be preserved to the 

 best advantage in tin. 



The earthenware jar was brought out to offset the high cost of the 

 glass jars; some of these were glazed inside, some outside, and some 

 on both sides. They were generally sealed with a tin cap by means 

 of wax, though a few had earthen tops. Various forms were given 

 to these jars, and some may still be found which have been in use 

 for many years in rural districts. The earthenware jars had only 

 one advantage over glass, that is in cost, but they had the disadvan- 

 tage of having blow or sand holes. The earthenware jar is not used 

 to any large extent in commercial canning, though some are used to 

 pack bulk jams and stock for preserves, etc. 



The tin can is preeminently the container used in commercial can- 

 ning, and it is also used to a very large extent in home canning. 

 Those used for the latter purpose retain the deep ring about the open- 

 ing for the insertion of caps and sealing with wax; these are com- 

 mercialy known as wax-top cans. In commercial canning solder is 

 used exclusively for sealing stud hole or cap cans. The tin can has 

 undergone a number of changes. The first cans had flush sides and 

 ends, or plumb joints; these gave way to the stamped-overlapped 

 ends, and all inside soldering has been superseded by lock seams and 

 outside soldering. Most solder caps are hemmed, so that only the 

 amount necessary to seal is used. The solder can has been super- 

 seded in many cases by the open top, or so-called sanitary can, and 

 in this case the sealing is done by double seaming on the top, no 

 solder being used on the can except in making the side seam. The 

 former objections to acid and solder, on the ground that they con- 

 taminated the foodstuffs, have thus been largely overcome. 



