Wash and clean your jars. It is no longer necessary to sterilize jars before canning (hurray!) but you should make sure they are preheated enough to not crack when placed in hot water.
Wash your lids with hot soapy water and place them in a clean bowl.
Add the tomatoes to a pot of boiling water and parboil them until you see the skins start to come off the tomatoes (about 1-2 minutes).
Use a slotted spoon and remove the tomatoes and place in the ice water.
Working with the tomatoes one at a time, remove any skin that hasn't already slipped off.
Drain the pot you parboiled the tomatoes in, and add one-third of the skinned tomatoes to it. Cook over medium heat to maintain a gentle boil, stirring often.
Using a potato masher, gently crush the tomatoes to release juices. Add another one-third of the tomatoes, and gently crush those as well.
Add the final third of tomatoes, and maintain the pot at a low boil for 5 minutes. Stir often to prevent scorching.
Add 3 quarts of water to your pressure canner and put it on a burner set to high. Make sure there is a canning rack in the bottom of the canner.
Add lemon juice or citric acid to your canning jars (see notes below for exact measurements).
Using a canning funnel, ladle hot tomatoes into the jars. Pack the tomatoes using a spoon to smoosh them down until they are covered in their own juices. Leave 1/2 inch headspace.
Using a long utensil (I prefer a plastic chopstick), remove all the air bubbles from the jar.
Clean the rim of the jar very well with a hot damp rag. Place a clean lid on the jar. Add a ring, and tighten to fingertip tight.
Place the jars in the canner. Lock the lid. Soon, steam will start coming through the vent pipe. Allow the steam to pass through for about 10 minutes. Then put the pressure regulator on top. (see photos in post above to see this in action)
Pretty soon, the air vent will pop up. That is a sign that you’re starting to build pressure inside the canner. Stewed tomatoes need to be pressure canned at 10 pounds of pressure for 15 minutes for both pints and quarts.
When the dial gauge reaches 10 pounds of pressure, reduce the burner temp to medium, and start your timer. The pressure must stay at 10 or (a little bit) above for the duration of the cooking time. You’ll likely need to adjust the temp on the burner a few times depending on your stove.
When the time is up, remove the canner from the burner and allow it to sit until you hear a distinctive “click” of the air vent dropping. Remove the pressure regulator and carefully remove the lid (Pro tip: I always use oven mitts when I take the lid off because the steam is crazy hot).
Let the jars sit for 5 minutes in the canner and then lift them out with canning tongs. Place on a towel where they can sit undisturbed for 12 hours.
After a few hours, to check for sealing, gently press down in the middle of the lid. If the lid has no give, it’s sealed. If you can press the lid in and it pops a bit, your jars are not sealed. You can reprocess them or store them in the fridge or freezer (only freeze jars that are wide mouth).
Water Bath Canning Instructions
Follow steps 1-10 above in the Pressure Canning Instructions.
Prepare your water bath canner by filling it with water. You just need to have enough water to cover the jars by 2 inches once the water is boiling.
Set the canner on the stove. Turn the burner to high. Once it reaches a boil, reduce it to simmer. You want to keep the water hot so that everything is ready when the tomatoes are
Follow steps 12-15 above in the Pressure Canning Instructions
Return the water in the canner to a rolling boil.
Using canning tongs, carefully lower the jars into the boiling water and place the lid on and set your timer.
Pints should process for 35 minutes, and quarts for 45. Pro tip: the water must return to a boil in the canner before you can start the timer.
Once the stewed tomatoes have processed for the appropriate amount of time, remove the canner from the burner, carefully take off the lid, and allow it to sit for 5 minutes. Pro tip: I tend to just slide it into the middle of my stove, as it weighs a ton.
Carefully remove the jars using canning tongs, and place them on a thick towel in a place where they can be undisturbed for 12 hours. The lids should start to pop within 20-30 minutes of being removed from the water.
Quarts: 2 tbsp lemon juice OR 1/2 tsp citric acid. Salt (optional) 1 tspPints: 1 tbsp lemon juice OR 1/4 tsp citric acid. Salt (optional) 1/2 tsp22 lbs tomatoes per 7 quarts, or 14 lbs tomatoes per 9 pints. About 3 lbs tomatoes per quart.Store in a cool dark place for 9-12 months.Flavored Stewed Tomatoes (From Ball Blue Book of Canning) MUST be pressure canned.4 quarts tomatoes 1 cup chopped celery 1/2 cup chopped onion 1/4 cup chopped green pepper 1 tbsp sugar 2 tsp saltCombine all ingredients in a large saucepan. Cover and cook for 10 minutes. Follow directions 11-21 in recipe card above for Pressure Canning instructions.