Canning Tomatoes Activity

Jars of canned tomatoes

Jars of canned tomatoes.
Rebecca Baxley, ©2021, Clemson Extension

Adapted from:  So Easy to Preserve, 6th ed., p. 151

Please read Using Boiling Water Canners handout before beginning.


1 ¼ pounds of tomatoes per jar
¼ teaspoon citric acid per pint jar
½ teaspoon salt per pint jar (if desired)

Part 1 – Preparing the Canner and Jars

  1. Wash hands thoroughly with soap and water for 10-15 seconds, rinse well, and dry.
  2. Assemble equipment and ingredients.
  3. Fill boiling water canner, with rack, half full of clean hot water. Heat water in canner to just under boiling (180℉) for hot packs. Keep hot while you continue with steps of procedure.
  4. Examine jars carefully. Discard any with cracks or chips in the rim. Examine ring bands and discard any with rust or bends. These imperfections could prevent a seal from forming.
  5. Wash jars thoroughly in warm soapy water, rinse well, and then place the empty jars upright on the rack in the boiling water canner to stay warm until ready to fill with the tomatoes.
  6. Label lids with permanent marker with name of product and date (and initials).
  7. Prepare lids and ring bands according to manufacturer’s recommendations.
  8. Heat 3 to 4 cups hot water in a medium saucepan or electric hot-pot for adding to canner if needed.

Part 2 – Preparing the Tomatoes

  1. While preparing the tomatoes, fill a large stockpot about half full of water and bring to a boil. (You need enough to keep boiling while you boil all your tomatoes a few at a time.)
  2. Wash tomatoes and cut an “x” in the skin at the bottom of each tomato with the tip of a paring knife.
  3. Fill a large bowl with very cold or ice water.
  4. Place tomatoes in boiling water for 30 to 60 seconds or just until skins split, then immediately remove tomatoes with slotted spoon and place in cold or ice water.
  5. Slip off the tomato skins and discard them. Place tomatoes on clean cutting board and core them. Carefully use a paring knife to only remove the inner, more firm core. Do not remove all the seeds and gel-like sacs or liquid.
  6. Trim away any undesirable portions, such as hard core or sunburned areas. Cut tomatoes into halves.
  7. Empty the large stockpot of water, and wash it out, if re-using.
  8. For the hot pack, put halved tomatoes in a large saucepan and add enough water to completely cover them. Bring to a boil and boil tomatoes gently for 5 minutes.

Part 3 – Filling the Jars

  1. Remove jars from hot water with jar lifter, emptying water back into the canner.  Place jars upright on towel – covered countertop or cake cooling rack.
  2. Add ¼ teaspoon citric acid or 1 tablespoon bottled lemon juice to each pint jar.
  3. Add 1 teaspoon salt to each jar, if desired for flavor.
  4. For hot pack, rest funnel in a hot pint jar.  Use a slotted spoon or ladle to fill hot tomato halves into the jars, leaving ½ inch from the top of the tomatoes to the top of the jar rim.  This gap is called headspace.  Add  hot cooking liquid to cover the tomatoes, leaving ½ inch headspace.
  5. Remove air bubbles by moving bubble-freer or plastic spatula gently in and out around the inside edge of the jar.  Air bubbles trapped in the tomatoes will rise as the tomatoes heat and can increase the headspace so that a seal and/or proper vacuum may not form.  Liquid may also no longer cover the tomatoes after cooling.
  6. Add or remove liquid with a spoon, if needed, to leave ½ inch headspace.
  7. Wipe jar rims with a clean, damp paper towel.  Anything on the rim could interfere with sealing.
  8. Apply lids according to manufacturer’s directions.  For two-piece metal lids, tighten bands over flat lids until fingertip tight.  Fingertip tight is when you meet firm resistance as you turn the band on the jar.  If a band is too tight, then air cannot escape and a seal might not form.  If a band is too loose, then liquid could escape from the jar and a seal might not form.

Part 4 – Boiling Water Canner Process

  1. Check the temperature of the water in canner.  For a hot pack, 180℉ (simmering) is the desired temperature.  Adjust the burner, if necessary.
  2. Use a jar lifter to place the jars of tomatoes one at a time on the rack in the canner.  Keep jars upright at all times.  Again, anything in the rim area might prevent the seal from forming.  Make sure water is 1 to 2 inches above tops of jars.  Add hot water from the saucepan or electric hot-pot if needed, pouring between jars rather than directly on top of jars.
  3. Place the lid on the canner and turn heat to high.  Bring water in canner to a vigorous boil, and then begin a timer set for your process time.  If the water ever stops boiling, return the water to a boil and start timing the full process again.
  4. Turn off heat after water has boiled continuously for the allotted process time. Remove the canner lid, lifting the underside away from you to direct steam away from your face.  Wait 5 minutes for contents to settle in jars.
  5. Remove jars one at a time with a jar lifter, being careful not to tilt them. If there is water on the lid, it will cool with the jar and may even run off during cooling.  Place jars at least one inch apart on a towel or cake-cooling rack.  Place away from drafts of moving air.
  6. Let jars cool, undisturbed, for 12 to 24 hours, then check for seals. Lids will be curved inward when properly sealed.
  7. Remove ring bands from sealed jars. Wash and dry ring bands to store separately for future use. Put unsealed jars in the refrigerator for use first.
  8. Wash, rinse and dry jars and jar threads to remove residues. Make sure they are clean everywhere.  Re-label if necessary.
  9. Store sealed jars in a cool, dry, dark place. Product maintains best quality for one year.

Recommended process time for water-packed Whole or Halved Tomatoes in a boiling-water canner

Style of Pack: Hot and Raw
Jar Size: Pints
Process Time at Altitudes of:
0-1,000 ft = 40 min
1,001-3,000 ft = 45 min
3,001-6,000 ft = 50 min
Above 6,000 ft = 55 min

Lesson Plan Adapted from:

Christian, K.A. and Andress, E.L. (2017).  Canning Tomatoes Lesson Plan.  Athens, GA:  Cooperative Extension, University of Georgia.

Source: Adapted from National Center for Home Food Preservation

If this document didn’t answer your questions, please contact HGIC at or 1-888-656-9988.

Factsheet Number



Pin It on Pinterest

Share This