The Safest Ways to Sanitize and Sterilize Your Jars

It’s an age-old debate, and likely one that you’ve found yourself engaged in with old-fashioned canning enthusiasts and new-age canners alike from time to time. Do you need to sterilize your canning jars? The short answer is… yes, most of the time. But if you’re unsure of whether you need to sterilize – or how, exactly, to do it – rest assured that a little bit of extra work never hurt anyone.

Knowing the exact methods you can use to sterilize your canning jars will help make the whole thing safer when it comes to getting ready for home canning season this fall.

Why You Need to Do This…

It may seem foolish to sterilize your canning jars before you are going to submit them to boiling hot temperatures during the canning process, but the reality is that sterilizing is a vital step in the food preservation process.

You must sterilize your jars to remove any lingering yeasts, bacteria, or fungi so that the food you place inside the jar is safe and not contaminated. Food that is canned inside dirty jars will spoil more quickly than normal.

Some argue that you don’t need to sterilize jars for water bath canning as long as the processing time is more than ten minutes, as this sterilizes the food and the jars. Many also believe that sterilization is not necessary for pressure canning.

However, it’s good to get yourself into the habit of cleaning your jars as thoroughly as you can. According to the National Center for Home Food Preservation, jars, at the very minimum, need to be washed with hot water with detergent or washed in a dishwasher.

Make sure to remove all detergent to eliminate the likelihood of odd flavorings or contamination, and also keep in mind that washing alone does not serve as a substitute for sterilization.

Sanitize or Sterile? Here’s How to Know Which One You Need

By now you’re probably a little confuses with the terminology: sanitizing, sterilizing? Is there a difference? Should I do both? Let’s clear things up before we get to the actual steps…

So first of all, yes, sanitizing and sterilizing (glass) jars are two different things. The former takes care of things like dust, glass chips, or traces of old produce, while the second takes care of microorganisms.

Which one do you need? Things get a little complicated, but not too much – I promise!

If you’re using your jars to store things like coffee, oatmeal, lentils, sugar, etc. – then sanitizing them is enough. You don’t need to sterilize them.

If you’re using your jars for canning, there are two distinct cases…

Case 1: if the canning recipe asks you to process the jars filled with produce for less than 10 minutes in a water bath or pressure canner, then you need to do both: first clean them, then sterilize them for 10 minutes with the only approved method (which I’ll talk about below).

Case 2: if you are going to process the jars for over 10 minutes, then the jars will sterilize, anyway. In this case, you only need to was them.

Let me help you visualize what we just talked about with this handy table:

Jar use case	Wash?	Sterilize?	Notes
Storing dry goods	✅ Yes	❌ No	Washing alone is enough
Canning — processed less than 10 minutes	✅ Yes	✅ Yes	Wash first, then boil jars for 10+ minutes (only approved method)
Canning — processed 10+ minutes	✅ Yes	❌ No	Jars sterilize during canning — no separate step needed

Do I Need to Clean Brand New Jars?

The short answer – absolutely. New canning jars, even when pulled directly out of the box, are not clean by any stretch of the imagination. A box or plastic wrap is definitely NOT a sterile environment, and packaged jars can be contaminated by microorganisms, dust, debris, and even chips of glass.

Washing is mandatory before every cycle of canning, regardless of the age or condition of the jars. Make a good, thorough washing the bare minimum in your cleaning process. This should be done without fail every time you can your own food.

When you wash your jars, you should inspect them carefully for any cracks.

You should also remove any scales or film from hard water by soaking them for several hours in a mixture of water and vinegar.

You can sterilize your jars while you are preparing your other ingredients for caning, which will allow you to make good use of the time spent waiting.

The Boiling Water Method (Safest Way to STERILIZE Jars)

As alluded to above, this is the only safe way to sterilize (not sanitize!) the jars. A.k.a. to kill the microorganisms. This needs to be done after you cleaned and removed the larger pieces of debris.

You already need to get your canner ready for the canning process – so why not make good use of that time and double up by sterilizing your jars at the same time?

Start by washing your jars as usual before placing them in a water bath canner. Alternatively, you can place them on a rack set inside a deep pot. Either way, the empty jars should be then covered with hot water, and have no bands or lids on them.

Bring the water to a boil and allow the jars to boil for 10 minutes. Steam will start to emerge from the pot. If you are using this method at an altitude above 1,000 feet, you will need to add an additional minute of boiling time for every 1,000 feet of elevation.

Turn off the heat and let the jars remain in the hot water. When you are ready to fill the jars, you should flip them upside down on a towel to dry – just make sure they remain hot.

The Dishwasher Method (Best Way to Sanitize Jars)

If you have a dishwasher – particularly one with a high-temperature setting – this is the go-to option for sanitizing your jars. Note that this does NOT sterilize them – even though to you they may look squeaky-clean!

Start by filling your dishwasher with cold jars. Run it either on its minimum run time setting or simply a rinse cycle – just make sure the rinse is done at the highest temperature setting possible.

After the cycle is done, keep the dishwasher closed to lock in the heat. You may pull one jar at a time so that the jars stay warm while you are packing them.

Washing Jars by Hand (Also a Good Way to Sanitize Them)

If you don’t have a dishwasher, a good ol’ kitchen sponge and some dish soap are all you need to give your jars a good clear. Again, this won’t sterilize them, but if you need to can them for more than 10 minutes or so, you don’t need to – sanitizing them is enough.

❌ Sterilizing Jars in the Oven?

Sterilizing your jars in the oven is one of the easiest and most convenient ways to sterilize your jars. It might take a bit longer than some of the other methods of sterilizing your jars, but despite this, still only takes about half an hour in total.

Now, before we move on, we need to address the elephant in the room because I can hear some of you reading cracking your knuckles about to take me to task down in the comments for recommending oven sterilization of canning jars.

Oven sterilization is a highly controversial topic. I know that many people, including people in my own family, who were brought up canning and taught to use the oven to sterilize their jars.

Whether you were taught by your mother or grandmother or someone else, it stands to reason they are a trusted figure who knew what they were talking about, and if you’ve been canning for any length of time using this method and had no trouble you’re probably content going right on with it.

But there’s a contingent of canners out there, a large contingent (see here and here), including some very smart people that decry the use of the home oven as a method of sterilization. They have some pretty good reasons which I will list below…

The National Center for Home Food Preservation itself states that:

Manufacturers of canning jars do not recommend baking or oven canning in the jars

Here’s why…

Inconsistent temperature– One of the chief complaints that detractors of oven sterilization level at the technique is that home ovens simply are not that accurate when it comes to heat control.

The temperature indicator on your oven is probably woefully inadequate, and combined with the uneven distribution of heat along with the periodic opening of the door to check on your progress means that your jars might not be held at the prescribed temperature the entire time…

Canning jars are not designed for oven heating– Probably the most damning charge against using the oven for sterilizing a glass jar, of any brand, is that the jars themselves are not designed for it.

Specifically, unlike glass bakeware canning jars are not made of tempered glass. this means that they will not withstand uneven heating and temperature shock very well at all, and you’re more likely to shatter your jars in the oven than you would using boiling or another method.

This complaint reached such a fever pitch that mason jar manufacturer Ball has addressed it in an FAQ on their site, and confirmed that their jars, of any size, are not for use in an oven- even at the relatively low temperature needed for sterilization.

Vulnerability to temperature shock- Compared with water bath sterilization which will consistently and evenly heat your jars to the prescribed temperature and keep it there, the nature of using an oven for the same purpose means that once your jars are done they are going to be more vulnerable to temperature shock when you pull them out.

Even setting them down on the countertop might be enough to cause them to crack or shatter entirely. This is still a concern when using water immersion, but it is more pronounced when using the oven.

Oven sterilization, despite these complaints, is still a viable method and one that’s been used for a very, very long time with success. If you are worried about it, simply pick another method…

❌ Can You Do It In a Microwave?

This is another popular sanitation method, but keep in mind that it obviously shouldn’t be done with any jars that have metal components (such as those airtight jars with a rubber and metal gaskets).

This one is also NOT a way to sterilize them, either (since now you know the difference!) – and here’s why: Microwaves, as you well know, tend to heat food and all other surfaces inside them very unevenly…

That’s why that leftover slice of pizza you tried to nuke at midnight comes out with one part that is as hot as the surface of the sun but the other part still is chilly as it was when you pulled it out of the fridge!

Worse, microwaves don’t have thermometers, and any thermometer you have cannot be used inside the compartment when it is turned on. 

This is not promising when it comes to sterilizing jars, and is one of the reasons why we leave the jars wet when we put them in; the idea is that the water, as it turns to steam, kills the germs. I would avoid this one, just like I would avoid the oven.

Sanitation Best Practices

When you sterilize canning jars, there are a few tips and tricks you should keep in mind to do it right..

First, you should never use old bands if they are rusty or damaged in any way. Not only do these have a higher risk of contaminating your food, but they will also fail to make a good seal. Toss them, and start over.

You should remove jars from your dishwasher only when they are ready to be used. Otherwise, they can cool down too much and will be exposed to more bacteria.

On that note, you should always clean more jars than you think you might need. You want to have plenty on hand in case you prepare more canning ingredients than you initially thought!

When you are preparing to sanitize your jars, make sure the area around your canning surface is completely clean. There’s no point in spending all this time cleaning the jars if the rest of the area is filthy!

They can easily pick up bacteria and other contaminants from the surrounding area. Therefore, any place you set your jars down – such as dish towels or bare countertops – should be clean and fresh.

Finally, you should always avoid adding cold food to hot jars, and hot food to cold jars. This can cause cracking and damage.

Picking the Best Jars for Canning

Making sure your jars are of high quality can also help make your sterilization process a little easier. Only buy bottles or jars that are designed specifically for canning, and don’t reuse containers from around the house, as these won’t be able to hold up to the heat. Canning jars are made out of tempered glass and should not have any nicks or cracks.

Jars should have flat, gasket-lined metal lids. These should be accompanied by screw bands that can be reused from time to time. You can sterilize your bands exactly as you would your jars.

They will also come with lids. These cannot be reused, no matter how well they are sterilized, and you will need to purchase new lids for every round of canning.

Should You Preheat the Lids?

Not anymore! The guidelines for doing it have changes, so it’s one less thing to worry about. The manufacturer of the Ball canning lids says:

Preheating Ball® lids is not advised. The sealing compound used for our home canning lids performs better at room temperature than it does pre-heated in simmering water (180°F). Simply wash lids in hot, soapy water, dry, and set aside until needed. Preheating can lead to less vacuum being achieved during water bath canning, and to buckle failures during pressure canning.

This advice is also given by Maine University here, by the way.

Which Cleaning Method Best?

If you read the whole thing thoroughly, then the answer should be obvious:

• to sanitize (clean) jars, either use a dishwasher or do it by hand
• to sterilize them, first sanitize them, then boil them for 10 minutes

Yet again (it’s worth repeating), remember that while sterilizing canning jars isn’t always absolutely necessary as a separate process, it does need to happen at some point – when you will try a new recipe. If the recipe says to boil the produce for under 10 minutes (or more depending on your altitude), then you do need to sterilize them in boiling water.