Canning update: successful jar sealing

Successful jar sealing often begins, and ends, with the lids.  Home canning requires use of a 2-piece sealing system, a flat metal lid and a metal band. Several years ago, manufacturers such as Ball changed the design of the lids to increase rust resistance and seal-ability and most lids no longer need to be preheated.  Boiling of lids may actually contribute to seal failure.

Here are some tips for making sure that jars seal, and stay sealed, so you can safely enjoy the bounty of the harvest all year long:

  • Canning lids are ‘one trip’; they are for one canning use only.
  • Wash jars and lids in warm soapy water and rinse prior to use. Inspect jars for cracks or nicks, especially on the sealing surface. Set aside any lids where the plastisol (sealant) has pulled away from the lid.
  • Follow manufacturer’s directions for pre-treating lids (yes, read the instructions printed on the box!) While Ball-branded lids no longer require preheating, other manufacturers may still require this step. [I tend to keep my lids warm, not boiling, along with my jars. While not necessary, a warmed lid is readied for sealing.]
  • Use a research tested recipe for preparing your canned item.
  • Fill warm jars and set headspace as directed in a tested recipe. Remove air bubbles.

    Back to Basics steam canner

  • Clean sealing rim and apply metal band finger-tip tight. The purpose of the band is to hold the lid over the jar opening, not to seal the jar. Air needs to escape from under the lid during canning! Tighten the band until you feel resistance. Over-tightening the bands risks jar breakage or seal failure.
  • For acid foods, use a boiling water canner or a steam canner for processing. Immerse jars in a boiling water canner with water at 180°F (hot-pack) or 140°F (raw-pack), place the lid on the pot, and wait for water to actively boil before you start timing the process. Water must cover jars by 1-2” during the timed process. Alternately, place filled jars on a rack above heated water in a steam canner (Wisconsin Extension has tested both Back to Basics and Victorio steam canners and each works well); place the dome lid on the steam canner and wait for a full column of steam to appear and the timing to begin. Information on safely using a steam canner is available from the Division of Extension.
  • For low-acid meats and vegetables, place sealed jars in 2-3 inches of warm water in a pressure canner. Follow manufacturer’s instructions for venting the pressure canner and the processing time in a tested recipe.
  • Once timing is completed turn off the heat and, if desired, wait 5 minutes before removing jars. (Optional step)

    Victorio steam canner.

  • Place processed jars on a rack and allow to cool away from drafts. Do not touch the lids!
  • Once jars are cool, check for sealing. Do not force lids to seal by pressing on the lid.
  • Store sealed jars in a cool, dry location. For ideal quality, use within one year. Screw bands should be removed before storage and the outside of jars washed with soapy water, gently dried.
  • Unsealed jars should be placed in the refrigerator and used within a few days, or frozen.

What if jars fail to seal? Review directions for using jars and lids and solutions for problems with canned foods. If all signs point to a lid failure as the cause of a jar not sealing, contact the manufacturer for more information. For Ball-branded lids or jars, call the company at 1-800-240-3340.

Interested in more updates? Join the blog. Stay well and safe preserving, Barb