Preserving FAQ

Preserving Frequently Asked Questions

Whether you're new or experienced, questions on home canning come up. We have compiled some of the common questions we have received over the years. 

  • General
    • What are the sizes of canning jars?

      Half cup (125 mL) 

      Half-pint or 1 cup (250mL)  

      Pint or 2 cups (500 mL) 

      Quart or 4 cups (1L) 

      Jams and jellies are only processed in jars up to a pint or 2 cups. All other canning may be processed in larger jars, depending on the recipe. Always follow the jar size given in a recipe. 

    • How will my processing time change if I want to do a smaller or larger jar size?

      If you want to use a smaller jar size, still use the processing time in the recipe.  

      Do not use a jar size larger than what is in the recipe as the processing time will be incorrect. 

    • Can I use any glass jar for processing?

      Not all glass jars are made to withstand the constant heating and cooling of processing your own foods. Only process with glass jars made for home canning.  

    • Can I use my glass lids in canning?

      Glass lids may be used for canning however, new rubber rings must be used each time. Soften rubber rings in hot water for 5 minutes. Stretch gently onto glass lids that have been sterilized in boiling water for 15 minutes or as required. After the jar is filled, place the lid on the clean jar rim. Apply screw band tightly and then turn back 1/2 inch to allow the air to vent during processing. Once processing time is complete, carefully retighten the screw band immediately after jars are removed from the canner. Do not turn jars upside down as seals may be broken. 

    • What can I use if I don't have a water bath canner?

      Any deep pot with a lid, such as a stockpot, that allows for at least 1 inch (2.5 cm) of water above jars may be used in place of a boiling water canner. A rack, such as a cake cooling rack, may be used to elevate jars off the bottom of the canner. A deep pressure canner may also be used; place the lid loosely on the pressure canner. Do not lock the lid into place and leave the vent open so that steam escapes and pressure does not build up inside. 

    • Is it possible to do canning on a smooth stove top? On a barbecue?

      Yes, canning is possible on a smooth top stove, but not recommended on a barbecue. To use on a smooth stovetop, you need to follow the instructions in your stovetop manual regarding the size of the pot to use. You must be able to maintain constant heat, not on a burner that cycles on and off. The canner or pot you use must have a flat bottom and not be ribbed like traditional canners. A stockpot could be used to water bath process smaller numbers of jars at a time.

      Canning on a barbecue is not recommended. It can be hard to maintain a constant temperature and boil the entire time needed; wind and weather will affect this. You must watch the pot the entire time. Also, many barbecue burners are not large enough to heat a large pot evenly. 

    • Why are oven canning and kettle canning outdated methods?

      Oven canning and open kettle canning are outdated and unsafe methods for preserving. In oven canning, the dry uneven heating was insufficient to destroy spoilage microorganisms and could also have caused jars to explode. In open kettle canning, food was cooked and then packed into hot jars and sealed without processing. The temperature obtained in open kettle canning was not high enough to destroy all spoilage microorganisms that may have been present in the filled jars. 

    • What do you mean by "fingertip tight"?

      “Fingertip tight” allows some give between the lid and jar and allows air to escape during processing. This creates a vacuum seal as the product cools. 

    • What is headspace?

      The unfilled space in a home canning jar. Allows for your product to expand and for the air to escape the jar to create an anaerobic environment.   

    • What do I do if my jars haven't sealed properly?

      Jams and jellies can be reprocessed within 48 hours of initial processing. 

    • What do you mean by reprocessing?

      Reprocessing is when you do the processing again because of a problem such as forgetting an ingredient or a jam or jelly that did not set. All steps need to be redone for this to be safe. 

      Reprocessing will affect the quality of your final product as you will need to re-heat the contents as well as reprocess. Pickles, chutneys, etc. can go very soft and lose quality. We recommend refrigerating any jar that has not successfully sealed. 

  • Jams & Jellies
    • What is gel stage?

      The gel stage is when a jam or jelly made without pectin has reached the point where it will form a gel. If you test it and it is not at the gel stage, continue cooking a few minutes longer. 

    • How can I test for gel stage?

      Temperature test: First, take the temperature of boiling water. You must do this each time as the temperature of boiling water can vary depending on the altitude of where you are and the weather on that day. Then add 8*F to the water temperature. This is now the temperature that your jam or jelly must get to. You must use a candy or deep-fry thermometer and not a meat thermometer. 

      Refrigerator or plate test: Place a small plate in the freezer at the beginning of your preserve making. To test for gelling, turn off the heat under your pot, place a small spoonful of the cooked recipe on the chilled plate and return to the freezer for 1 minute. Remove the plate from the freezer and separate the product with a spoon. If it is set and does not run together, the preserve is ready. 

    • Can I use liquid pectin in a recipe that calls for pectin crystals, and vice versa?

      No. Each type of pectin uses a specific recipe. For the best chance at good results follow your recipe as directed.  

    • My recipe calls for 1 package of liquid pectin, does this mean the whole box or one pouch?

      One package is 2 pouches of pectin. If you are using an older recipe it may state 1 bottle, so use 2 pouches. 

  • Pickles
  • Pie Filling
    • Why can't I use flour in my pie filling?

      Due to the updated research in this area, we know that flour in home-canned goods is not deemed safe. Always follow an updated tested recipe from a reliable source. 

    • What is Clearjel?

      It is a modified food starch that is approved for use in home canning.  

      Do not use instant Clearjel in home canning.

Important Preserving Info

Research is continually being conducted in the area of home canning. As a result, recommendations may change. Current preserving and food safety information recommend that all home-canned foods be processed. Visit our page on the basics and important information here.


ATCO Blue Flame Kitchen information and recommendations contained in this publication have been researched and are in accordance with current guidelines published by Bernardin Ltd. and the Cooperative Extension Service, University of Georgia. We acknowledge their assistance. The Bernardin Ltd. "Guide to Home Preserving" is available at retail outlets in Alberta. 

The methods and procedures outlined in this publication are recognized as safe. Many factors over which we have no control may cause spoilage. ATCO Blue Flame Kitchen assumes no responsibility for any failures or spoilage that may occur. 

For further questions or concerns, contact us.