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 full diameter of the can open for filling. That part of the cover that comes into contact with the can is coated with a compound or fitted with a paper gasket or ring which makes a perfect seal when the cover is crimped on the can. Some mechanical device is necessary for sealing this can, and this is the sealer.
Cans may be had with inside enamel or plain without any enamel. The following fruits and vegetables should be canned in enamel-lined cans: All berry fruits, cherries, plums, rhubarb, pumpkin, beets and squash. All highly colored products should be canned in enamel-lined cans to prevent the bleaching effect induced by their action upon the plain tin. Some prefer to can fish and meat in the enamel-lined cans. Other products not mentioned here may be canned in plain cans, since they are less expensive than the enamel-lined cans.
Covers are lined in two ways, with the paper gasket and the compound gasket. The compound gasket is merely a preparation, scarcely visible, applied to the under side of the cover and is not easily damaged by handling. The paper gasket is a ring placed on the under side of the cover and must be handled carefully. If the paper gasket becomes broken the cover must be discarded. To sterilize covers having the paper gasket, place them in the oven for a few minutes, but do not wet them, before sealing cans. Do not remove or handle paper gaskets.
When the cans are removed from the cooker the ends should be raised; this is caused by the pressure within. If they are not raised at the ends the cans should be carefully examined for defects. After the cans are sterilized they should be cooled off in water. This will cause the ends to collapse. If they do not collapse the reason is probably due to overfilling. It must be remembered that peas, beans and corn swell a certain amount after water is placed in the cans; therefore, in canning these vegetables the cans should be filled only to within a quarter of an inch of the top. If the pressure of the air from without will not cause the end to collapse, it should be forced in by hand.
THE TINNING OUTFIT
Tin-can sealers are made to handle the regular Number 2, or pint cans, and the Number 3, or quart cans. The sizes are interchangeable, so that in a few minutes' time a Number 2 machine may be changed into a Number 3 machine with the necessary attachments. So it is economy to buy a machine with these attachments, as you can then use either pints or quarts as you desire.