and safe test:

Put one tablespoon of water into an empty can and seal. Have on hand a
vessel containing enough boiling water to cover the can. Set aside
and, as soon as bubbles disappear from the surface, immerse the can in
the hot water. This heats the water in the can and creates a pressure
within the can. Keep the can under the surface for two minutes, and if
by that time no bubbles rise from the can the can has been sealed
air-tight.

ADJUSTING THE SEAMING ROLLS

If bubbles rise from the can the seam is not sufficiently tight. If
this seam is not sufficiently tight the _second_ seaming roll needs
adjusting, provided the directions regarding seaming rolls given below
have been observed. To set the rolls proceed as follows: Loosen the
nut on the bottom of the seaming-roll pin. With a screw driver turn
the seaming-roll pin counter clockwise--that is, from right to left.
Turn very slightly and, while holding the seaming-roll pin with the
screw driver in the left hand, tighten nut with the right hand, and
test as before.

Occasionally it is well to compare the seam after the first operation
with the sample can which is sent with the machine.

If seaming rolls cut into the can they are set too close, and the
seaming-roll pin should be adjusted in the opposite direction from
above.

After adjusting, always test cans as suggested above before canning.
The seaming rolls are set before the machine leaves the factory and
should not require adjusting for some time, but I have found that
slight variations in cans may make adjusting necessary.

If for any reason the second seaming roll is brought into contact with
the can before the first operation is complete it may injure the can
seriously, thus preventing an air-tight seam.

If the first seaming roll is forced in too rapidly it may ruin the
seam. Push the seaming-roll lever gently and steadily, while turning
the crank with the right hand. This rolls the seam gradually. There is
no danger from bringing in the second seaming roll too quickly if the
first seaming roll has completed its work.

There are thus, as you see, two kinds of tin cans used in home
canning: The sanitary or rim-seal can, which is used with a sealer,
and the cap-and-hole can. The latter consists of a can, and a cover
which carries a rim of solder and is fastened on the can by the
application of heat.

The sanitary can has a cover a trifle larger than the diameter of the
can, thus leaving the