                    Care Of Pressure Canning Equipment



To preserve low-acid foods which are safe, good tasting and
nutritious, you need to correctly use equipment which is
well-maintained and in good operating condition. 

Safety Vents or Petcocks:

    -     Be sure the vent is clear and unobstructed.  Use Q-tip
          or cotton string to clean.
    -     Be sure vent tubes are screwed tightly into lid.
    -     If it is a model with vent under the handle, be sure
          the lever is moving freely.
    -     If it is a model with a petcock, be sure it opens and
          closes freely, either by screwing or flipping the lever
          up and down.
    -     If there is a film from hard water on the petcock, and
          it can be unscrewed from the lid, soak the parts in
          vinegar, then wash and dry.
    -     A ball and socket type petcock can be cleaned with
          silver polish.

Safety Overpressure Plugs:

    -     If it is a metal alloy or composition metal plug that
          screws into the lid, do not try to remove it.
    -     If it is a rubber plug, use the thumbnail test to see
          if the rubber is still pliable enough.  If pressure
          with thumbnail leaves a permanent dent in the rubber it
          is too brittle for safe use and should be replaced.
    -     If either type of plug has been blown out by
          overpressure in the canner, it must be replaced by a
          new plug. Do not try to reuse the plug that blew out. 

Gaskets:

    -     Soak gasket in hot water for an hour to soften before
          the first use of the season.
    -     Insert gasket into its groove in lid.  If it is either
          too shrunken to fit to the edge, or too stretched to
          lie smoothly in the lid, it must be replaced. 
    -     Use thumbnail test - if pressure with thumbnail leaves
          a permanent dent in rubber, it is too brittle and
          should be replaced. Rubber safety plug should be
          replaced at the same time, since it will probably be
          too brittle also. 

Pressure Gauge:

    -     Have dial and pop-up gauges tested every year before
          canning season at your local Cooperative Extension
          Office.  If it is inaccurate it must be replaced.
    -     Check entrance port and carefully remove any debris
          that may have accumulated.
    -     Be sure gauge is screwed firmly into lid.  If it
          attaches with a nut on the underside of the lid, be
          sure the nut is tight.

Weighted Pressure Regulators:

    -     Have no moving parts so there is no need to have them
          tested for accuracy.
    -     Be sure they are clean, with no debris or food residue
          encrusted especially in the sockets where the weight
          fits over its vent.
    -     Be sure the entrance port and vent pipe are open and
          unobstructed. 
    -     Be sure there are no nicks or damage to the weight or
          to the tip of the vent pipe where the weight fits.

Canner Lids: 

    -     Be sure handles are securely attached.
    -     Be sure gasket fits smoothly into its groove in the
          lid.
    -     Set lid on canner and turn to lock it into place. It
          should turn on smoothly and easily.
    -     If it does not turn on easily, check to be sure gasket
          is properly seated in its groove. Adjust if necessary.
    -     If the gasket is properly seated, check the lid. If the
          lid is warped or bent, it might be replaceable. Contact
          the manufacturer. If it is an old model or no longer
          manufactured, there may be no way to continue using it
          as a pressure canner.  It may be used as a regular pot
          for cooking.  If this is the case, remove the gasket,
          and if possible open or remove the gauge and
          overpressure plugs or petcocks, to avoid the
          possibility of pressure buildup.
    -     If there is no visible problem but the lid continues to
          be tight, a small amount of petroleum jelly or cooking
          oil may be applied to the gasket to lubricate it. 

Canner:

    -     Be sure there is a rack in the canner. 
    -     Check the bottom for flatness. Older model canners may
          warp if overheated. If the bottom is not flat or the
          canner will not sit flat on the heating element or
          burner of the stove, it should not be used for canning.
          Warped canners may be used for cooking. Once warped,
          the damage can not be reversed. 
    -     Put 1 inch of water in the canner, close the lid, heat
          the water and pressurize the canner.  Check to see if
          steam is escaping at any point other than the petcock
          or safety vent.
    -     If steam is escaping around the gasket and it seems to
          be properly in place, a small amount of petroleum
          jelly, or cooking oil, may be rubbed around the gasket.

          This will soften it and help it to seat more securely. 
          Too much oil or jelly will over-soften the rubber, and
          will leave a sticky residue on the canner. 

    -     With weighted gauge canners, if the weight only hisses
          continuously and does not rock or jiggle intermittently
          as the manufacturers' directions specify, check to see
          if the stove is level. This type of weight must hang in
          a centered position on a vertical vent. If the stove is
          not level the weight will not hang properly and steam
          will escape in a continuous stream from the side, and
          pressure will not build up properly. 
    -     If steam is escaping around the base of any of the
          vents (dial gauge, weight vent, safety vent, petcock)
          where they screw into the lid, and if you can screw
          them out of the lid, the threads can be wrapped with
          plumber's tape to seal them. Plumber's tape is a
          stretchy, non-sticky silicon tape used to seal threads.
          It is available in small rolls from a hardware store. 
          Be sure to wrap the tape in the right direction, so
          that when you screw the vent back into the lid, the
          direction of the turning does not unwrap the tape.

Canner Use

    -     Follow manufacturers' directions for use of your
          particular model.
    -     Use canner on the appropriately sized burner.  A canner
          should not hang over the edge of the burner by more
          than 2 inches on either side. 
    -     Be sure to center the canner on the burner.  Some
          ranges do not allow enough space to center a large
          canner on rear burners.
    -     Be sure lid is securely locked on (turned on, or
          screwed down).
    -     If your canner has six or eight large screws and wing
          nuts to close it, screw them down in opposite pairs. If
          there are six, screw numbers 1 and 4 down part way,
          then 2 and 5, then 3 and 6, then return to the first
          pair to finish tightening continuing around the lid.
    -     For all models, be sure to vent the canner for 10
          minutes on high heat with a full stream of steam
          escaping.  This is necessary to remove air from the
          canner.  Air remaining inside will lower the maximum
          temperature achievable, and may cause underprocessing
          of the food.  After the 10 min. venting, close the
          petcock, or place the safety weight or weighted
          pressure regulator on the vent. Allow the pressure to
          build to 10 psig, or to 5 or 15 psig if you are
          processing at those pressures. (psig means Pounds per
          Square Inch by Gauge, the measure of pressure.)  Be
          sure that you use the proper time for the pressure
          level that you are using.  Check the new USDA Home
          Canning Guide for safe recommendations.
    -     When canner reaches the specified pressure, begin
          counting the processing time. 
    -     Reduce heat gradually to maintain the pressure without
          over-pressurizing. With a weighted pressure regulator,
          leaving the heat on too high will not increase the
          pressure, but will cause excess steam loss from the
          canner, since steam will be escaping continuously. 
          Surpassing the specified pressure in a dial gauge
          canner will result in soft, mushy or darkened food, and
          excessive vitamin loss. 
    -     If the pressure drops below its proper level during
          processing, increase the heat to bring the pressure
          back up, then begin the timing over again from zero,
          for the full specified time.  
    -     Never run cold water over a canner to cool it. While
          newer, lightweight aluminum canners will not warp the
          way old ones did, the full, slow cool-down time is
          necessary for adequate process time. Shortening the
          time by cooling the canner with water is unsafe. In
          addition, excessively rapid cooling may cause jars in
          the canner to crack or explode as the pressure in the
          canner drops more rapidly than the pressure in the
          jars. 


    -     When the pressure has dropped to zero, wait another 1
          minute before opening the canner.  On some models the
          pressure drop will be visible when the overpressure
          plug drops back into the lid, the rubber plug is no
          longer bulged, or the dial gauge will read zero. 
          Smaller canners will take at least 30 minutes to cool,
          larger ones may take over an hour.  
    -     Open the petcock or remove the safety weight carefully
          and wait until any rush of steam has stopped. Then open
          the lid and tilt the back edge up first, so that it
          directs the steam away from your face. 
    -     Remove the jars immediately. Do not leave jars sitting
          in a hot canner overnight, spoilage may result. 

Canner Storage:

    -     It is acceptable to leave clean water in the canner if
          you are going to be canning again the next day. However
          if much juice from the jars escaped and the water in
          the canner is colored it should be discarded. 
    -     Turn the lid upside down and rest it on the canner. The
          weight of the lid should not be resting on the gasket
          during storage as it could deform it.
    -     For long-term storage at the end of the season, wash
          and dry the canner well. Be sure all the parts (safety
          weight, rack, etc.) are in the canner. A few crumpled
          newspapers in 1the canner will absorb moisture and
          odors.
    -     If you unscrew the gauge or vents, coat the threads
          lightly with petroleum jelly to prevent rust and make
          them easier to replace.
    -     Coat the gasket very lightly with petroleum jelly or
          oil.
 

Burpee, Health, National Victory and Dixie canners are no longer
manufactured, and no parts or service are available for these
canners.  Parts and service are available for Presto, Mirro and
All American, and for some models of National Presto, Kwik Kook,
Steamliner and Maid of Honor. If you need further assistance or
have other problems, contact your local Cooperative Extension
Office.    

If you are thinking of buying a canner at a garage sale, check to
be sure you can open and close the petcocks.  Look for stains of
drips down the sides or on the lid near the vents, they may
indicate that the lid does not seal or leaks steam all the time. 
Check that the lid twists on and off easily.  Check the condition
of the gasket.  Check that the base is flat. A rounded base
indicates that the canner is warped.  Check that there is a rack.

Buying any of the models listed above as having parts and service
available is a much better bet than one of the older ones.  


Prepared by Mary A. Keith, Foods and Nutrition, August, 1991   
Revised by M. Susan Brewer, Foods and Nutrition, June, 1992      

 EHE-704

