522 U. S. BUREAU OF FISHERIES 



forated steam pipes. Upright exhausters, in wiiich the cans travel 

 along a spiral, are also in use. By this means the contents of the 

 can are heated and the greater part of the air exhausted, which is the 

 object of the first cooking in the retort under the method formerly in 

 general use. In Alaska, where 1-pound tall cans form the bulk of the 

 pack, the cans are exhausted at a temperature from 206° to 212° F., 

 210° being the favorite. 



A recent invention, which the inventor claims will do away with 

 the steam exhaust box, and thus save a large amovmt of valuable 

 floor space in the canning "line," is the power vacuum pump, known 

 as vacuum exhausting machine, by means of which air is exhausted 

 from the cans, accomplishing the same purpose as the steam exhaust 

 box. Some of these machines have been in active use for several 

 seasons, \\'ith most satisfactory results. Double seamers in which a 

 vacuum is created in the can before the top is sealed on are now 

 rapidly superseding other types, incidentally doing away with the 

 steam exhauster, thus greatfy reducing the amount of space required 

 and doing away with the impleasantly damp steam which leaked 

 from the steam exhauster. 



Leaving the exhauster, the cans pass to the double seamer, which 

 fastens the cover on tightly with a double seam or crimp. It should 

 be stated that no solder is used in attaching the top on the can, the 

 curled flanges of the cover being coated around the outer edge with 

 cement or other sealing fluid to take its place. Solder, however, is 

 used in joining the side seam of the can, this being done when the can 

 is manufactured. The cans then leave the machine on an endless 

 conveyer, pass through a machine which washes the outside of the 

 cans, and thence to the men who transfer them to the coolers, which 

 are immediately placed upon the trucks and run into the retort for 

 the one cooking they are to receive. By the use o^ these cans the 

 soldering machine used in the old-style method is done away with. 

 It also does away with the first cooking and the subsequent venting 

 and soldering, a saving both in labor and time consumed. 



COOKING 



The processing time varies in each district and sometimes for each 

 species. In Alaska 1-pound tall reds, cohos, chums, and pinks are 

 generally cooked from 90 to 120 minutes, at 12 to 18 pounds pressure 

 and at a temperature of 242° to 248° F. One-pound flats and half- 

 pound cans are generally cooked about 10 minutes less time. Owing 

 to their larger bones, king salmon are generally cooked from 10 to 20 

 minutes longer than the other species; steelhead trout also. 



On Puget Sound 1 -pound tall sockeyes, cohos, and pinks are 

 generally cooked for 90 minutes at a pressure of 10 pounds and at 

 a temperature of 240° F. Plalves and 1 -pound flats are generally 

 cooked at the same temperature but for only 80 minutes. Chum 

 talis are generally cooked for 105 minutes at a pressure of 10 pounds 

 and at a temperature of 240° ; while spring or king salmon are cooked 

 for 120 minutes at a pressure of 10 pounds and at a temperature 

 of 240°. 



It is the custom at all canneries, no matter what the system, to 

 allow about 5 minutes at the beginning of the cooking to work up the 

 required heat of the retort, and when cooking is comnleted there is 



