16 



MASS. EXPERIMENT STATION BULLETIN 341 



less of pressure release conditions, e.g., rapidly or slowly. For example, the 

 average vacuum attained in 16 fully sealed jars was 25.6 inches and in the 

 partially sealed jars, 27.6 inches when the pressure in the cooker was released 

 rapidly; when the pressure was released slowly, the average vacuums were 

 24.1 and 28 inches, respectively. Normal variations in headspace and variations 

 in filling temperatures ranging from 70° to 212° F. had no effect on resulting 

 vacuums. The vacuum range was 19.2 to 26.7 inches in 72 glass jars heat 

 processed for 20 minutes in a water bath with the headspace of 65 to 72 cc. 

 and filling temperatures of from 70° to 210° F. More detailed and extensive 

 data on the subject of vacuum-pressure relationships in glass jars during 

 processing are given in the theses of Maclinn (6) and Levine (5). 



Table 2. — ■ Effect of Type of Seal on Vacuum as Determined by the 

 Vacuum Desiccator and the Water Displacement Methods 



COOPERATIVE CANNING EXPERIMENTS WITH HOME CANNERS 



During July and August of 1935 some 5,586 all-glass jars were distributed to 

 experienced home canners of western Massachusetts with the stipulation that 

 all processing of these jars be done with the bail tightened, i.e., fully sealed. 

 Each cooperator was also provided with new rubber rings, a set of instructions 

 and precautions, a book of canning recipes, and a form sheet to be returned to 

 the laboratory. The form sheet was to contain data on loss of liquid and 

 breakage during processing. In addition to the new jars distributed, almost 

 12,000 old jars were used in the canning experiment. 



