No. 2 (1921) REMARKS ON CANNING 6/ 



The steamed fish being externally wet from the condensed 

 steam have to be dried ; this is readily done by exposing the 

 grilles to the sun or placing them in a drier. In America huge 

 rotary steam heated ovens are often used for drying or 'baking ' 

 the steamed fish: such oven consists of a vertical axle with 

 horizontal shelves radiating from it ; the whole is enclosed in a 

 casing in which it slowly revolves: the grilles are placed on the 

 shelves at an opening and remain in the oven during one revolu- 

 tion of the machine which usually occupies about 5 minutes; on 

 re-arrival at the opening the grilles are removed. 



64. The fried or steamed fish are then emptied from the grilles 

 on to the packing tables which have been described above. Thence 

 the packed tins, with covers inserted, are taken to the next room 

 for closing either by soldering or by seaming. When closed they 

 have to be tested for leaks ; hence in this room there must be one 

 or two testing vats heated either by open fire or by kerosene stove 

 or by steam ; if steam is available this is the best arrangement, 

 viz., a vat of wood or masonry or metal with a closed coilof steam 

 pipe at the bottom, over which is placed a perforated false bottom; 

 see paragraph lOI for the method of testing. These same vats are 

 used for ' exhausting ' (see paragraphs 103— 109) the tested cans : 

 moreover, if the open pan processing system (see paragraphs III — 

 129) is used in the factory these or adjacent pans can be used for 

 processing. These pans can be heated by open fire or by steam 

 as is most convenient ; steam of course is desirable since water is 

 more readily and steadily heated than by open fire. 



65. If the pressure system of processing is adopted there must 

 be either one or two autoclaves or else retorts (kettles) steamed 

 from an external boiler. As inferable from its name, the autoclave 

 is self-contained and produces its own steam; it is a strong iron 

 vessel, usually cylindrical and vertical, set over an open fire ; in 

 this vessel a moderate amount of water is placed and brought to 

 the boil, and the cage (perforated metal cylinder) loaded with 

 cans is then lowered into it ; its cover is then secured steam tight 

 and the fire urged so that the water in the vessel is driven into 

 steam, which having no outlet, rapidly comes to the desired 

 pressure. The cover is fitted with safety valves, a thermometer, 

 and a blow-off cock. A geared hoist by the side of the autoclave 

 is absolutely necessary to lift and lower the heavy cages. In the 

 separate retort system a strong metal vessel either cylindrical and 



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