Glass-top Jars.—Fit top to jar. If top rocks when tapped it should not be used on that jar. The top bail should not be too tight nor too loose. If either too tight or too loose the bail should be taken off and bent until it goes into place with a light snap. All sharp edges on top and jar should be filed or scraped off.
Screw-top Jars.—Use only enameled, lacquered or vulcanized tops. Screw the top on tightly without the rubber. If thumb nail can be inserted between top and jar, the top is defective. If the edge is only slightly uneven it can be bent so that it is usable. Put on the rubber and screw on the top tightly, and then pull the rubber out. If the rubber returns to place the top does not fit properly and should not be used on that jar.
Rubbers.—Be very particular about the rubbers used. Buy new rubbers every year as they deteriorate from one season to another. It is always well to test rubbers when buying. A good rubber will return to its original size when stretched. When pinched it does not crease. It should fit the neck of the jar snugly, and be fairly wide and thick. It is cheaper to discard a doubtful rubber than to lose a jar of canned goods.
Grading
Vegetables and fruits should be sorted according to color, size and ripeness. This is called grading. It insures the best pack and uniformity of flavor and texture to the canned product, which is always desirable.
Blanching and Cold-Dipping
The most important steps in canning are the preliminary steps of blanching, cold-dipping, packing in hot, clean containers, adding hot water at once, then immediately half sealing jars and putting into the sterilizer. Spoilage of products is nearly always due to carelessness in one of these steps. Blanching is necessary with all vegetables and many fruits. It insures thorough cleansing and removes objectionable odors and flavors and excess acids. It reduces the bulk of greens and causes shrinkage of fruits, increasing the quantity which may be packed in a container, which saves storage space.
Blanching consists of plunging the vegetables or fruits into boiling water for a short time. For doing this place them in a wire basket or piece of cheesecloth. The blanching time varies from one to fifteen minutes, as shown in the time-table.