REFRIGERATION OF FISH 



557 



vapor pressure (that is, the tendency to evaporate) of water or ice 

 increases with rising temperature. The tendency of water vapor to 

 condense increases with a lowering temperature. Water will evapo- 

 rate, therefore, from warm objects and condense on cold ones. The 

 pipes are usually the coldest objects in the room — perhaps several 

 degrees colder than the fish. The ice slowly evaporates from the fish 

 and condenses as snow on the pipes. When the temperature of the 

 room and the fish rises a few degrees temporarily, evaporation is 

 increased. Therefore, provision is made to prevent warm air from 

 entering the storage room when the doors are opened. Sometimes 

 a canvas curtain is used at doors and elevator openings. The brine 

 or ammonia is kept at a temperature as nearly uniform as possible. 



Fig. 19. — Halibut and salmon frozen and stored in bulk in a private freezer, Pacific 

 coast. Courtesy, Canadian Fishing Co. (Ltd.) 



PLACING FISH IN STOREROOMS 



In public freezers, where the fish are boxed, the boxes are placed 

 in the rooms, usually standing on end, and stacked to the ceilings. 

 Dunnage is often, though not always, put on the floors to permit 

 circulation of cold air under the boxes. Bins usually are built for 

 fish not frozen in cakes. Such bins serve to hold the fish and to 

 keep lots separate. Bait herring are dumped without arrangement 

 into large bins. 



In private freezers, especially those used chiefly for halibut and 

 salmon, the frozen fish are stacked in an orderly way without boxing. 

 One method of arrangement is to put dunnage on the floor, then pile 

 the fish to the ceiling in a solid rectangular block, leaving only a 



