12 BULLETIN 1465, U. S. DEPARTMENT OF AGRICULTURE 
When the kettle was operated for the first time during the day it 
was brought up to the required pressure of 65 pounds very slowly. 
The valves were opened several times to blow off the condensa- 
tion water and carry out the air. As the pressure in the kettle grad- 
ually increased and reached 65 pounds, the pressure in the boiler 
was dropped to that point, as there was no pressure-reducing valve 
in the system. The pressure and temperature in the kettle depended 
directly on the pressure of steam in the boiler, and it was only by 
good boiler management that the pressure remained even and at the 
maximum. 
REMOVING AND SEALING THE CANS 
At the termination of the necessary period of steaming, the valve 
in the steam line from the boiler was closed and the pressure in the 
kettle released as quickly as safety would permit. It was desired to 
remove the cans while they were hot. Usually three persons took 
part in this operation, each one having specific tasks to perform. 
Efficient speed was highly desirable. The lid of the kettle was loos- 
ened as the pressure diminished, so that as soon as the pressure gauge 
fell the last time the lid was thrown back. The volume of rising 
water vapor and heat carried the dust away from the kettle, though 
the building was usually sprayed previously from an overhead sprink- 
ler to keep down any dust. The thermometer cable and bulb were 
removed. The surfaces of the cans were quickly and thoroughly 
flamed with a gasoline blowtorch and the covers put on. The three 
cans in the top layer were lifted out and the lower three cans were 
flamed and covered. As each can was lifted out the rim was painted 
with sterile glue and a piece of sterilized heavy canvas cloth was 
wound around it, closing the joint between the cover and the can. 
The hole in the center of the cover was closed with a double piece of 
adhesive tape, as was the hexagonal opening. All of these openings 
were thoroughly flamed with the gasoline torch several times in the 
interval between their removal from the kettle and sealing. 
The act of sealing had to be accurately and expertly done (pi. 4), 
as a defect would inevitably have resulted in contamination. The 
tape had to remain in place for an indefinite time and endure much 
hard usage. As soon as the six cans had been prepared for sealing and 
none of them needed further immediate care, the canvas strip and 
adhesive tape joints were painted with a good quality of spar varnish 
and repainted several times as soon as the previous coat dried. 
The cans were then set out of doors, to remain sealed until they were 
ready to be planted. The kettle was loaded again and the process 
repeated. By efficient handling, three persons could remove and 
seal the six cans taken from the kettle in about 15 minutes. 
PREPARATION OF TAPES, GLUE, VARNISH, ETC. 
The strips of canvas cloth 2 inches wide which were used around the 
covers were torn to the right dimensions. They were well wrapped 
in paper and sterilized by steam. An adhesive tape 2 inches wide 
was also used around the cans, and this was usually sterile as re- 
ceived from the manufacturer. It was treated further by pasteur- 
izing on three successive days. The tape used to seal the openings 
in the cover was treated in the same manner and was uniformly 
sterile. 
