434 MARINE PRODUCTS OF COMMERCE 



retorts. The coolers, filled with hot cans, are then passed through a "lye wash" 

 to remove oil, washed with clean water, and finally set aside on the floor of a 

 warehouse overnight to cool. As the interior of the cans are at high temperature 

 and pressure, any leaks which are present will show as bubbles of air in the "lye 

 wash." Most of the defective cans are removed in this way; however, they are 

 tested further, after being washed with hot water, by being tapped on the 

 distended ends with a short metal rod. Any can which has a dull sound is dis- 

 carded, as it is an indication that it is leaking; a ringing sound means that con- 

 siderable pressure exists within. 



Of course, there are some minor variations in methods of canning salmon: such 

 as running the open cans through the "exhaust box," thus dispensing with the 

 "clincher" machine; also, sealing the cans under a vacuum produced by vacuum 

 pumps, thus eliminating the "exhaust box." As already described the cans pass 

 automatically from the filling machine into the "coolers" by means of belts and 

 conveyors; for this reason it is obvious that each piece of machinery, including 

 fillers, "clinchers," "exhaust box," and closing machine, must work in perfect 

 synchronism. 



Another type of "exhaust box," which has been installed in some of the canneries, 

 obtains a vacuum in the canned salmon by means of a "steam jet." In this method 

 the filled cans are passed through a short box just before entering the sealing 

 machines. This box is fitted with open steam jets directed at the fish at the open 

 end of the can. After a short exposure to these jets of steam on each side of the 

 line of cans, the lids are dropped in place and the cans are immediately sealed. 

 In using this method it is not necessary to heat the contents of the can to obtain 

 a satisfactory vacuum. 



After the retorted cans are cooled, they are sometimes lacquered in an automatic 

 machine. However, there is an increasing tendency to do away with lacquering and 

 to depend on enameled ends and labels to prevent rusting of the cans. The cans 



(.Courtesy U. S. Fish and Wildlife Service) 



Fig. 20-7. After the cans of salmon are sealed they are processed so that they are 

 practically sterile. This is done in a retort under 10 lbs. steam pressure. 



