Michigan State University Extension
Preserving Food Safely - 01600497
10/13/97

### CANNING JARS

        Food  may be canned in glass jars or metal  containers.

    Metal
     containers  can  be used  only  once.   They  require

    special
     sealing  equipment and are much  more  costly  than

    jars.

        Regular  and  wide-mouth  Mason-type,  threaded,  home-

    canning
     jars  with self-sealing lids are the  best  choice.

    They
    are available in 1/2 pint, pint, 1-1/2 pint, quart  and

    1/2
     gallon sizes.  The standard jar mouth opening is  about

    2-3/8
     inches.   Wide-mouth jars have openings  of  about  3

    inches,
     making them more easily filled and emptied.   Half-

    gallon
     jars  may  be  used  for  canning  very acid juices.

    With
     careful  use  and  handling, Mason jars may  be reused

    many
     times,  requiring only new lids each time.  When  lids

    are
     used  properly,  jar  seals  and  vacuums are excellent

    and
    jar breakage is rare.

        It  is  recommended that mason-type jars  designed  for

    home
     canning  be used for preserving food  by  pressure  or

    boiling-water-bath
      canning.   However,   some   commercial

    pint
    and quart size mayonnaise or salad dressing jars may be

    utilized
    for canning  acid  foods in  a boiling-water canner

    when
    new 2-piece  lids are used.  However, you should expect

    more
    seal failures and jar breakage.

        Commercial  mayonnaise  jars are weakened  by  repeated

    contact
     with  metal  spoons or knives  used  in  dispensing

    mayonnaise.
     Seemingly insignificant scratches in the  glass

    jars
     may cause the jars to crack or break  during  boiling-

    water
    canning.  Commercial jars are not recommended for  use

    in
     pressure processing.  It is recognized that some  people

    continue
     to  can  products  successfully  using  commercial

    mayonnaise
     jars  with new 2-piece lids.   However,  use  of

    mason-type
     jars designed for use in home canning ensures  a

    safe
    product and break-free jars during processing.

        Other  commercial  jars  with  mouths  that  cannot  be

    sealed
    with two piece canning lids are  not recommended  for

    use
    in canning any foods at home.

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