It's So Easy

It's so easy to can… with Kerr Jars, Caps and Lids

The jar and cap play an important part and it is poor economy to use a container or cap that may not seal. Choose only standard, reliable jars, made and intended for home canning. These have the manufacturer's name blown in the glass. BE SURE the jar cap properly fits the jar on which it is used. SCREW BANDS must be used with the lids and the bands must be in good condition.

Before beginning to can, READ CANNING INSTRUCTIONS and recipes carefully to be sure you have chosen the correct method for that particular food. Above all BE SURE THE PROCESSING TIME IS CORRECT. No Matter how carefully food may have been selected and prepared, if not processed long enough, it will spoil.

The first rule for successful canning is the SELECTION OF SOUND, firm-ripe fresh foods. Over-mature and bruised foods can produce spoilage in the canned product. Fruits and tomatoes should be firm but well ripened. Vegetables should be young and tender.

WASH ALL FOODS THOROUGHLY before preparing them. Sort tomatoes, berries, cherries and plums, discarding all spoiled or bruised ones. Large fruits such as peaches, apples and pears should be washed before peeling and all trace of bruised or decayed spots removed. Cut well around these defective parts. Many time the fruit around them is soured and this soured portion may cause the entire jar to spoil.


All foods spoil because of the action of micro-organisms known as MOLDS, YEAST and BACTERIA. These are on the food, in water, air and soil. In canning, their action must be stopped by the proper application of heat and the jars of food must seal air-tight after processing so micro-organisms (in the air) cannot enter the jar.

Molds and Yeast

Subjecting yeast and molds to the temperature of boiling water for a few minutes will usually stop their growth.


BACTERIA is more difficult to destroy. The AMOUNT and KIND OF BACTERIA on foods may also vary. Some are more heat resistant than others. The acid in fruits and tomatoes is not favorable to the development of bacteria; therefore, acid foods are easiest to can. Cooking food sufficiently for table use is not enough to stop the growth of spoilage organisms. For this reason, it is VERY IMPORTANT to PROCESS FOOD THE FULL PERIOD OF TIME SUGGESTED IN RELIABLE TIME TABLES and make sure the temperature being applied is correct. If this is not done, spoilage may result later.

IF NOT DESTROYED BY HEAT, yeast and many types of BACTERIA CAN GROW IN A SEALED JAR. When food in the sealed jar begins to spoil, the seal will usually release. This is not the fault of the jar or cap, but indicates spoilage organisms in the food that were not destroyed or rendered inactive by the processing.


Enzymes that can cause discolorations, loss of flavor and texture are in the raw fruits and vegetables. The action of the enzymes is destroyed by proper processing of the food.

Fruits, tomatoes, rhubarb and pickled vegetables are best processed in a boiling water bath canner. For all other vegetables and all meats, or meat and vegetable mixtures, a pressure cooker should be used.

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How Kerr Mason Caps Seal

Kerr Mason Caps, "Self Sealing" Brand, seal by vacuum which forms during the cooling of the contents of the jar. This vacuum is produced by packing boiling food into the jar and sealing the jar immediately, or by heating the food in the jar. If the jar of food is not processed, the degree of vacuum is influenced by the temperature of the content at the time the jar is sealed.

The application of heat (processing) causes the air and food in the jar to expand and escape from the jar by venting of the jar cap. Kerr Lids vent all during processing. This venting is essential in order to form a high vacuum. As the contents of the jar cools, the vacuum forms. The sealing composition in the Kerr Lid makes air-tight contact between the lid and glass, retaining the vacuum and preventing outside air from entering the jar during storage.


Properly prepared and properly canned foods can stand moderately high storage temperatures for considerable periods of time, but a cool, dry place with temperatures 70 degrees F. or below, will keep canned foods at their best.

Heat is more harmful than light and warm or hot storage temperatures will in time, cause loss of quality in canned foods. Storage in unheated basement or closets is usually satisfactory.

Canned foods should not be subjected to freezing as it may soften the texture of them, but it does not cause spoilage in the canned food unless it breaks the seal on the jar cap.

Opening Jars

To OPEN Jars sealed with KERR Caps, unscrew the band, (if you have not previously removed it,) puncture the lid with a sharp pointed instrument. Pry up on the tiny edge of the lid which turns down over the neck of the jar.

If screw band sticks to jar, place top of jar in boiling water for a few minutes or tap band lightly with knife handle and the band can be easily unscrewed.

Examining Canned Foods Before Using

  1. When a jar of canned vegetables or meat is opened, DO NOT TASTE THE COLD FOOD.
  2. Jars should show no signs of leakage, mold, fermentation or spurting of liquid when opened.
  3. The order of a jar of canned food, upon opening, should be characteristic of the product. If it does not smell right, if the food is exceptionally soft or cloudy in appearance, discard it at once.

AS A SAFEGUARD against using canned foods that may be affected with spoilage that is not readily detected, heat all low-acid foods (all meats and all vegetables except tomatoes) at boiling temperature 10-15 minutes before tasting or using. Many times odors that cannot be detected in the cold product, will be evident in the boiling food. This boiling will destroy certain toxins if they are present in the food. If, after boiling, food does not smell or look right, discard it without tasting.

Approximate Yields

LEGAL weight of a bushel of fruits or vegetables varies in different states. These are average weights:

(Above table reprinted from U.S. Dept. of Agriculture Bulletin AIS-64)
Food Fresh Canned
Apples 1 bu (48 lb.) 16 to 20 qt.
Apricots 1 bu. (56 lb.) 20 to 24 qt.
Berries, except strawberries 24-qt. crate 12 to 18 qt.
Cherries, as picked 1 bu. (56 lb.) 22 to 32 qt.
Peaches 1 bu. (48 lb.) 18 to 24 qt.
Pears 1 bu. (50 lb.) 20 to 25 qt.
Plums 1 bu. (56 lb.) 24 to 30 qt.
Strawberries 24-qt. create 12 to 16 qt.
Tomatoes 1 bu. (53 lb.) 15 to 20 qt.
Asparagus 1 bu. (45 lb.) 11 qt.
Beans, lima, in pods 1 bu. (32 lb.) 6 to 8 qt.
Beans, snap 1 bu. (30 lb.) 15 to 20 qt.
Beets, without tops 1 bu. (52 lb.) 17 to 20 qt.
Carrots, without tops 1 bu. (50 lb.) 16 to 20 qt.
Corn, sweet, in husks 1 bu. (35 lb.) 8 to 9 qt.
Okra 1 bu. (26 lb.) 17 qt.
Peas, green, in pods 1 bu. (30 lb.) 12 to 15 qt.
Pumpkin 50 lb. 15 qt.
Spinach 1 bu. (18 lb.) 6 to 9 qt.
Squash, summer 1 bu. (40 lb.) 16 to 20 qt.
Sweet Potatoes 1 bu. (55 lb.) 18 to 22 qt.
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