I know that canning is a daunting process to many. It was for me, too, until my sweet friend Jen took one summer day about 5 years ago to teach how to do it myself.

Once you see how someone else does it, the whole process begins to be demystified. My goal in showing you this tutorial is to remove the “I can’t do this” element of canning, and show you just how simple and do-able the process really is!

How to Can Diced Tomatoes Using the Boiling-Water Bath Method

Canning day begins. I don’t remember exactly, but I think I began with around 50-60 lbs of tomatoes (a mixture of my own garden toms, as well as some from the produce market). Notice the cleanliness of the kitchen and its surroundings. πŸ™‚

Here’s what you’ll need:

  • Tomatoes. It takes about 2 1/2 to 3 lbs to fill a quart jar, so either figure out how many lbs you have and plan your jars accordingly, or decide how many jars you’d like to make, and buy that many lbs of tomatoes.
  • Mason jars
  • Canning dome lids. These are the flat lids that usually come in boxes of 12. Any brand will do, so long as you have the right size (wide mouth, regular, etc.). ALWAYS use new lids, never re-use old ones.
  • Screw bands for each jar.
  • Lemon juice
  • Sea salt
  • Canning funnel (not absolutely necessary, but it makes it easier)
  • Jar lifter (these ARE necessary, for safety reasons)
  • Cookie sheet
  • Kitchen towels and washcloths
  • Canning pot, as well as a smaller pot
  • Several mid-size bowls, a strainer, and a slotted spoon

Getting Started

The first thing to do once your space is all clean and ready to go is to prepare the pots that you will use. It takes a long time for a huge canning pot full of water to begin boiling, so you want to get on that right away.

The pot on the right is the one that I use for the actual canning. The small one on the left I use for peeling the tomatoes.

I fill my canning pot most of the way full to start off with, because the water level will go down as it boils away, and you can always take some out, but if you don’t start with enough water, it takes a while to add more and get it back up to boiling.

Peeling the Tomatoes

Once I get the small pot of water boiling, it’s time to begin. At the same time, I will prepare a sink full of cold water and add a tray of ice cubes to keep it cool.

I fill it up with just enough tomatoes so that they are all completely covered (or at least, very close). I use an oven timer and set it to 30 seconds as soon as they go in. Occasionally a tomato will need closer to 45 seconds, but they usually end up getting close to that by the time I hear the beep and take them out anyways.

Some people like to make an “x” slit in the skin of the tomato before boiling it, to make the skin come off easier. I don’t bother and find that the skins still come off fine. It’s your call.

As soon as I’ve pulled the tomatoes out of the boiling water with a slotted spoon, I put them into my strainer and put the whole thing straight into my sink of cold water.

This stops the cooking process and makes them cool enough so that you can now handle them, remove the skin and cut them up easily, without a cooked, mushy mess on your hands!

A tomato with it’s peel just starting to come off. I often start it with a small slice of my paring knife, though sometimes the skin splits on its own and slicing it isn’t necessary.

A tomato that has been peeled. Still nice and firm and intact, easy for dicing.

Preparing the Tomatoes

Here’s my canning setup:

  1. Large pot on the left, for collecting the diced tomatoes that are ready to go on the stove.
  2. Bowl for the compost– to hold peels, or any parts of the tomato that need to be discarded.
  3. I think the third bowl (I took these pictures last summer!) also held peeled tomatoes, ready to be diced.
  4. This bowl is definitely full of peeled, cooled-off tomatoes.

I grab from the bowl on the right, diced up the tomato on the cutting board, discard any peels or un-usable parts, then push the diced pieces into the large pot.

It’s important to note here that you will be able to move the most quickly by grouping together like actions. By this I mean that you should peel a whole bunch of tomatoes at once, then diced a whole bunch at once. Then go back and boil/cool off more tomatoes, peel them all in a group, then diced them all in a group, etc.

Once you get into the rhythm of a particular action, it goes much more quickly if you focus on that one action and process the tomatoes in batches. I find that after a half hour or hour, I really get into the swing of it and begin to move smoothly from station to station in my kitchen, and then the work really begins to go more quickly. I also happen to find that once I get into my groove, it’s quite a soothing, peaceful process… (Am I strange? Do others find this as well?)

…except when I have a 4 week old colicky newborn, fussing in a sling. Ryan caught one picture of me where you can obviously see that I’m saying “shhh, shhh”. That was my canning mantra last summer, “Shhh, sweet baby. Go to sleep, Johanna. No more crying. Shhhh…” πŸ™‚

I realize that I missed a photo, and that is of my huge vat of diced tomatoes simmering on the stove. Once I get the pot a good 3/4 of the way full, I stick it on the back burner, on low-med heat, and continue on with my peeling and dicing while I occasionally stir and let the tomatoes get good and hot.

Get Your Jars and Lids Ready

Meanwhile, turn the oven on low (maybe 200-250), get out a cookie sheet, and put your clean, empty jars on the sheet. I like to pop mine into the oven for about 5-10 minutes before I fill them up with tomatoes, so that they are nice and warm before going into the Boiling-Water Bath.

This helps to prevent them from cracking once they’re in there, which is a frustrating waste, not to mention a mess. Heed my advice, ladies. Pre-warm your jars, even though you’re cooking your tomatoes first. It’s worth it.

While you’re doing this, get out a small saucepan or pot, and bring a couple inches of water to a low boil. Take the canning lids that you are planning to use (the flat dome lids) and put as many as you need for your first batch of jars in the hot water. Leave them for 5 minutes, then you can either let them stay there or take them out and put them on a clean towel. Those little magnetic canning wands are handy for this job, but I make do without one.

Fill Up the Jars

Take your cookie sheet out of the oven when you’re ready to fill the jars up. Using a canning funnel, fill each jar up until it is almost full.

Remember to leave headroom (this is the space at the top, between the rim of the jar and how high the tomatoes come up). A 1/2 inch of headroom should be sufficient.

To each of the jars add:

  • Lemon juice- 1 Tbsp for pints, 2 Tbsp for quarts
  • Sea salt- 1/2 tsp for prints, 1 tsp for quarts

Once everything is in the jars, give the rims a wipe with a clean, wet cloth. Now take your sterilized dome lids and place them on top of the jars.Β Then put on the screw caps (rings) tightly and seal those babies up.

The jars are ready to go into the boiling water bath!

Set them carefully in the wire holder, while it is perched up on the edges of the pot. This helps to keep you from getting burned by plopping them in and having water splash up, and also allows the jars to acclimatize to the water temperature more gradually.

Once full, slowly and carefully lower the jars completely into the pot, until they are fully submerged. You want to have a good couple of inches covering the tops of the lids, as this is what creates the pressure that will properly seal them and preserve the food. If there’s not enough water, they probably won’t seal properly.

Process the jars (keep them in the water) for:

Pint jars- 35 minutes
Quart jars- 45 minutes

Remove the Jars and Check the Seals

After this time, carefully lift the wire jar holder up out of the water, and rest it on the edge of the pot. Use canning tongs to grab each jar and lift it out of the water, then place it down onto the folded towels on the counter.

I put mine on top of double/triple towels on the counter. These jars are HOT! They can easily ruin a counter or leave heat marks on a nice table (not to mentioning burning a perfectly lovely person, such as yourself). Be careful with them.

Now listen for the “POP!”. This is how you know they’ve sealed. You will likely hear it at some point within 30 minutes of pulling them out of the water.

You can also check after a while by gently pushing down. If the lid moves up and down or you can feel a bit of give in it, it’s not sealed. You’ll want to take the lids off, rewipe the jar rim to make sure it’s clean and then put the lid back on tightly and re-process in the boiling water bath.

I leave mine sitting out overnight, to cool off completely. The next morning I double check all of the seals, and if they’re good, I remove the rings. If I find some that aren’t quite sealed, I decide whether to just use them quickly (if it’s only a couple jars- I can make a freezer meal or some spaghetti sauce for the freezer).

If there are more than 3-4 jars not sealed, then I’ll fill my big pot back up and boil them all over again. A pain, yes, but worth it. Always be on the safe side with your canning. Never take a chance. The risks are simply NOT worth it. Ever. This is your family’s health and safety. No inconvenience or even loss of food is worth compromising safety for.

You’re Done!

Sadly, I did all that work and forgot to take a picture of my 38 completed jars of tomatoes! They were beautiful, though, I tell ya. Tasty, too. And worth every bit of the effort, and mess.

Oh yes… last step. Clean your kitchen. Sigh a few times, and maybe grumble under your breath about why you’re doing this. Look at the clock at realize it’s 10:57pm and you should be in bed. Then get yourself a small bowl of ice cream, and sit and admire your hard work. πŸ™‚

Have you tried your hand at canning tomatoes?

Technical information is taken from Putting Food By, a very thorough resource for those who do canning of any kind. It has information on headroom, additives like salt or sugar, boiling time, altitude adjustments, overall safety and more. I still reference it multiple times each summer!