Canning 101

I’m relatively new to canning—the process of putting food into jars and making them shelf-stable so they can sit in your pantry for up to a year or longer—and at first it seemed super intimidating. While my mom had a water bath canner, she doesn’t know much about canning, which meant that my whole process of learning how to do this was done by reading as much as I could on the internet and then just giving it a try.

After a couple years of figuring out water bath canning, I got a pressure canner for Christmas. This greatly expanded my repertoire of canning recipes and has allowed me to also do things like meals in a jar.

If you’re brand new to canning, here’s what I’d consider the 101 to get you started:

Some Basic Terminology

• Canning: The process of putting food in jars and making them shelf-stable for long-term storage.
• Water Bath Canner: Some foods are processed by using a water bath canner, which processes and seals the jars by submerging them in boiling water.
• Pressure Canner: Other foods are processed by using a pressure canner, which operates similarly to a pressure cooker to raise the pressure (and thus the temperature) to achieve even hotter temperatures to process and seal jars. A pressure cooker cannot double as a pressure canner, even if the pressure cooker tells you it can be used for pressure canning.
• Headspace: When filling the jars, recipes say to leave a headspace of a certain amount. This is how “full” you make the jars; if the recipe calls for a headspace of an inch, you fill the jar to within an inch from the top.

Water Bath Canning

A water bath canner is essentially a large pot. It includes a rack that sits in the bottom of the pot so that the jars don’t touch the bottom. Once the filled jars are put in the pot, water is added to completely submerge the jars and cover with at least an inch of water. The stove is turned on and the once the water comes to a full boil, the processing time begins. If the water ever stops boiling, the water must come to a boil again and the processing time restarted. (So don’t turn down the temperature too much.)

As the water boils around the jars, the contents of the jars heat up and oxygen escapes. The wax rings on the lids soften. When processing is done, turn off the stove and let the water stop boiling. Let it sit for a few minutes, and then carefully remove the jars using a jar lifter and put them on a thick towel somewhere to sit overnight. Do not tilt the jars or lay them sideways; keep them upright until they’ve fully cooled overnight.

Foods processed using water bath canning are typically high-sugar or high-acid foods. Processing the jars in boiling water kills most pathogens, but there’s still a risk of botulism, which thrives in low-oxygen environments. Canning creates a low-oxygen environment in the jars, but the high-sugar or high-acid content inhibits the growth of botulism, making the foods safe to sit on a shelf and be eaten at a later date.

Pressure Canning

Like a water bath canner, a pressure canner is essentially a large pot. These ones have lockable lids, though, and equipment and attachments to raise the pressure within the pot and monitor that pressure.

I have a Presto 23-quart induction compatible pressure canner. This one comes with a screw gauge to regulate the pressure, but after reading several recommendations on the internet, I upgraded the screw gauge to a weighted gauge. So, rather than me having to constantly fiddle with the gauge through the processing time to ensure proper pressure is maintained, I instead just have to keep an eye on the weighted gauge to ensure it’s “rocking” properly, allowing me to do other things while my jars process. (If the pressure ever drops too low, then the pressure must be raised again and the processing time starts over.)

Pressure canners come with their own specific instructions on how to process jars, so always follow the instructions that come with your pressure canner.

Unlike water bath canning, jars in a pressure canner are not completely submerged. The pressure canner allows the water and steam to reach higher temperatures than can be achieved in a water bath canner, and it uses the steam to process the jars. Similar to water bath canning, most oxygen escapes from the jars and they sit on a thick towel overnight so that the lids properly seal.

Pressure canned foods do not have to be high-sugar or high-acid, because the higher processing temperature kills off any botulism that could be in the jars, making it safe to store in your pantry and eat at a later day.

General Safety Tips

• Always use lab-tested recipes. Because there are potentially serious health considerations when canning (botulism can kill you), always use recipes that have been fully tested. Some good places to find these recipes include Bernardin, Ball, and Healthy Canning (which generally compiles recipes from elsewhere, though they sometimes customize the seasoning a bit).
• Follow the recipe exactly. Part of what makes a recipe safe is the density of the food in the jars. If something is too dense, then heat cannot fully penetrate the jar and heat the food to the required level. So if a recipe calls for certain foods, do not swap them out for others or add something the recipe doesn’t call for. This also includes using bottled lemon juice rather than freshly-squeezed lemon juice, if the recipe calls for it, as bottled lemon juice is guaranteed to have a certain level of acidity that you can’t rely on fresh lemons providing.
• Some variations are allowed. Typically, the only variations that are safe to experiment with come down to any dried seasonings that are added. Always thoroughly research or access help from Master Food Preservers before proceeding.
• Adjust for altitude. If you’re 1,000 feet above sea level or higher, you have to adjust processing times, and weights in the case of pressure canning, to safely can and preserve foods. Ball has a handy chart here on their website.
• Use the recommended jar size or smaller. Always use the jar size the recipe calls for. You can go smaller if you wish. (I have a family of two, so sometimes I don’t want large jars of food that I open and then have to use up.) You cannot go larger. Going larger means that the contents of the jar might not heat to the necessary level, putting you at risk of food contaminated with bacteria or other microbes that could prove harmful.
• Be careful when doubling a recipe. In general, it’s okay to double or triple a recipe. It’s usually a good idea to write out the new ingredient quantities before you start canning so that you don’t get caught up trying to do doubling or tripling math on the fly. This does not apply to jams and jellies. Anything with pectin cannot be doubled or tripled unless it is a special type of pectin meant for doubling/tripling. If you try doubling a jam recipe, the jam will not set properly.
  • Before I knew this rule, I had tried doubling a recipe for ginger marmalade (which goes great on a baked brie). It didn’t set properly, so I threw it in the freezer just in case and used it as a cooking sauce for chicken.

• Always use new lids. You can reuse jars and the metal rims, but you must use a new lid each time. If you reuse a lid, the wax ring has already been used once and may not properly seal when used a second time.
• Sterilizing the jars is optional. A lot of recipes have you sterilizing the jars as step one. However, research has found that if the filled jars are processed for at least ten minutes, then any bacterial contaminants in the jar are killed off. If the recipe calls for the food to be processed for five minutes, you can generally double that to ten minutes with no effect on the food. If sterilizing the jars is something you want to do for that extra feeling of safety, definitely feel free to do so.
• Test the lids the next morning. After everything has fully cooled, test the lids in the morning to ensure a proper seal has formed. First is a visual inspection; the lids should be slightly curved inward due to a lack of air in the jars. Second is a manual inspection. Remove the rings and gently try to lift the lid off. If it’s stuck in place, it’s properly sealed. If the lid comes off easily, then the jar did not seal. Any unsealed jars should be put in the fridge and consumed promptly.
• Remove the rings when storing the jars. It’s generally recommended to store the jars without the rings. They could rust and adhere to the lid, or they could be holding the lid down in a way that makes it look like it’s sealed when it’s not. To be honest, I’m not the best with following this rule. I have, however, once gone to open a jar and after taking the ring off, discovered that the jar had never properly sealed and the ring was holding it in place. I had to throw out the contents of that jar, just in case.

Equipment You Need to Can

• Water bath canner, if wanting to do water bath canning
  • Here’s a decent looking one on Amazon
• Pressure canner, if wanting to do pressure canning
  • Here’s the Presto 23-quart induction compatible pressure canner I have
  • If you want to upgrade to a weighted gauge, this one is compatible with the above pressure canner
• Mason jars
  • You can order these on Amazon in the sizes you want, but I’ve found they’re usually cheaper at grocery stores, Canadian Tire, and Walmart
  • Jars can be reused as long as they are not cracked or chipped, so you can even sometimes find them at yard sales
  • You should not re-use pasta sauce jars or other similar jars, even if they say the word “mason” on them, since they may not be true mason jars and might crack during processing
• Metal rings
  • New jars come with metal rings, but when you start re-using jars you might need additional rings in case some get lost or become damaged
  • Again, you could order these on Amazon, but they’re usually cheaper in grocery stores, Canadian Tire, and Walmart
• Lids
  • New jars come with new lids, so you need these when you’re re-using jars and have discarded old lids
  • Again, you could order these on Amazon, but they’re usually cheaper in grocery stores, Canadian Tire, and Walmart
• Jar-lifter
  • Here’s a decent looking one on Amazon that comes with a magnetic lid lifter (see below)
• Digital Scale
  • Most recipes give measurements in weight, as that’s the most accurate
  • You don’t need a fancy one; this one looks fine
• Optional equipment
  • Funnel: I really like this. It makes it easy to get stuff in jars without making a mess all over the place, and some of them even have measurements on them so you can accurately assess headspace. This is the one I have; there are cheaper ones on Amazon but they don’t appear to have the measurements to help with headspace.
  • Magnetic lid lifter: If you sterilize your jars, you’re supposed to put the lids in lightly-simmering water to sterilize and warm them. A magnetic lid-lifter lets you pick them up from the hot water and put them on the jar without risking contaminating the underside with your fingers. (I don’t use one of these.) Here’s one that comes with a jar lifter, or here’s one that comes with scrapers.
  • Scraper: You’re supposed to scrape the insides of jars with a non-metal utensil to remove air bubbles that are trapped in the food. You can buy this sort of thing, or you can use a chopstick, or plastic cutlery. I just use a chopstick, but if you’re looking for a fancy one, here’s a couple scrapers that come with lid lifters.
  • Something to open jars: I used to pry them open with my fingernails and that usually ended with chipped fingernails. My mom found a paint can opener at Home Depot that works perfectly for prying off lids. I’ve found some bottle openers similarly do the trick if you can hook it under the lip of the lid. I can sometimes use the handle of a spoon or the ring from the jar to wedge between the lid lip and the glass thread on the jar, giving it a little twist and popping the lid off.