19. DEVICES FOR MEASURING.--Accurate measures are necessary in canning; in fact, some of the work cannot be done satisfactorily without them. A half-pint measuring cup and a quart measure with the cups marked on it are very satisfactory for making all measures.
Scales are often convenient, too. For measuring dry materials, they are always more accurate than measures. Many canning proportions and recipes call for the measurement of the ingredients by weight rather than by measure. When this is the case and a pair of scales is not convenient, it is almost impossible to be certain that the proportions are correct. For instance, if a recipe calls for a pound of sugar and an equal amount of fruit, a measuring cup will in no way indicate the correct quantity.
20. COLANDER AND WIRE STRAINER.--For the cleansing of fruits and vegetables that are to be canned, a colander is of great assistance; also, if a large wire strainer is purchased, it may be used as a sieve and for scalding and blanching, steps in canning that are explained later.
21. GLASS JARS.--For household canning, the most acceptable containers for food are glass jars that may be closed air-tight with jar rubbers and tops. Use is sometimes made of bottles, jars, and cans of various kinds that happen to be at hand, but never should they be employed unless they can be fitted with covers and made positively air-tight. Like utensils, the glass jars that are a part of the household supply should be used from year to year, if possible, but not at the loss of material. Such loss, however, will depend on the proper sealing of the jars, provided everything up to that point has been correctly done. All jars should be carefully inspected before they are used, because imperfect or broken edges are often responsible for the spoiling of food.
In purchasing glass jars, only what are known as first quality should be selected. Cheap jars are likely to be seconds and will not prove so satisfactory. Glass jars may be purchased in sizes that hold from 1/2 pint to 2 quarts. If possible, food should be canned in the size of jar that best suits the number of persons to be served.
If the family consists of two, pint jars will hold even more than may be used at one time, while if the family is large the contents of a quart jar may not be sufficient.
22. Numerous types of glass jars are to be had. Some of them are more convenient than others and may be made air-tight more easily. These two features are the most important to consider in making a selection. Jars that close with difficulty, especially if the tops screw on, are not likely to keep food successfully because the bacteria in the air will have a chance to enter and thus cause the food to spoil.
Glass jars used for canning foods have improved with canning methods. The old-style jars had a groove into which the cover fit, and melted sealing wax or rosin was poured into the space surrounding the cover. Later came the screw-top jar shown in Fig. 3. This type of jar has been extensively used with excellent results. Both the mouth of this jar and the jar top, which is made of metal, usually zinc, lined with glass or porcelain, have threads that match, and the jar is sealed by placing the jar rubber over the top, or ridge, of the jar and then screwing the jar top firmly in place. Such jars, however, are more difficult to make air-tight than some of the newer types. One of these jars is illustrated in Fig. 4. It is provided with a glass cover that fits on the ridge of the jar and a metal clasp that serves to hold the cover in place and to make the jar air-tight after a rubber is placed in position. Another convenient and simple type of glass jar, known as the automatic seal top, has a metal cover with a rubber attached.
Another improvement in jars is that the opening has been enlarged so that large fruits and vegetables, such as peaches, tomatoes, etc., can be packed into them whole. With such wide-mouthed jars, it is easier to pack the contents in an orderly manner and thus improve the appearance of the product. Besides, it is a simpler matter to clean such a jar than one that has a small opening.