Basics and Tips: How To Sterilize Glass Jars and Bottles

Because I’ve been making a lot of jam this summer, I figured that it was about time I did a ‘Basics and Tips’ post on how to sterilize glass jars and bottles. You know, so everyone can enjoy the taste of wild blueberries and elderflower during winter!

There are a number of different ways to sterilize glassware, but they are all incredibly easy. However, it’s important to remember that, whatever method you decide to go with, you should never put plastic or rubber lids in the oven, boiling water or the microwave. Check the inside of the metal lids to make sure they don’t have a rubber sealing ring on the inside. Although the plastic or rubber may not melt completely, the lid will probably not fit properly anymore. And when it comes to preserving food items, such as jams or syrups, it is very important that the lids make a good seal. For the same reason, you should discard rusty or damaged lids.

Furthermore, sterilizing means bringing the glassware up to a high temperature, so make sure to handle the glassware with care and take precautions so you won’t burn yourself.

Oven mitts are your best friends when it comes to sterilizing!

In the Oven

I have to admit, I’ve never tested this method myself (as I never have any newspapers), but I know there are a lot of people out there who would never think to sterilize glass bottles or jars any other way. 

To sterilize glassware in the oven, preheat the oven to 130°C (266°F). Any higher and the glass is likely to break. Place a double layer of newspaper on a baking sheet and place the glassware (and the lids) on top of it, arranging it so the jars don’t touch each other. Place the baking sheet in the middle of the oven, close the oven door and ‘bake’ (aka: sterilize) the jars for about 20 minutes. Wearing oven mitts, take the glassware out of the oven a few minutes before you’re ready to fill the jars. Place them on a folded tea towel or heatproof mat and fill them with hot jam or syrup.

In the Dishwasher

If you have a high temperature setting (at least 80°C or 176°F) or a steam function on your dishwasher, you can simply place the glassware in your machine, run a hot (rinse) cycle and fill the jars once the cycle is completed.

This is obviously a very easy method, but it may use up a lot of water. Furthermore, it can be difficult to time the ending of the cycle with whenever your jam or syrup is ready to be ladled into jars.

In the Microwave

It’s possible to sterilize jars in the microwave, but I wouldn’t know much about that; we don’t have a microwave…

On the Stove

Whenever I need some sterilized bottles or jars, I use this method. It’s very easy, quite fast and doesn’t require newspapers, microwave ovens or extreme dishwasher settings!

Place your glass jars, bottles and fitting screw top lids in a big pot (I always use a Dutch oven, because it’s the biggest pot I’ve got) filled with tepid water. Some people argue that you should start with cold water, but I don’t think it matters much. The idea is that you want the temperature of the glass to gradually come up, but the glass you want to sterilize is probably at room temperature already, so tepid (or even slightly warm) water is fine. Either way, you want to make sure the bottles and jars are completely submerged and that there is no air trapped inside them…

Oh, and put the pan on a back burner. It’s about to get very, very hot! Mine was actually on one of the front burners, but that was for blog purposes only…

Next, cover the pan with a lid…

… and fire up the stove!

Over high heat, bring the water to a rolling boil. Leave to boil for 10 minutes. Not 8 minutes. Not 9 minutes. 10! It’s fine if the bottles and jars happen to boil a little longer, but make sure they have boiled for at least 1o minutes! So set your kitchen timer…

This is mine. Isn’t it cute? Isn’t it adorable? My now 12-year-old nephew gave it to me as a housewarming gift when the Rocking Rebel and I moved into our home about a year ago.

Anyway, once the glassware and lids are a-cooking, I usually start cooking up the jam, because – conveniently enough – fruit usually needs to boil for about 10 minutes to turn into jam!

So after 10 minutes, turn off the heat and leave the bottles and jars submerged in the hot water, until you’re ready to fill them. It’s really important not to try and fill cool jars with hot jam or syrup, as the glass may shatter if you do! Trust me on this one. I used to work in a restaurant as a waitress and whenever a customer ordered an Irish Coffee, I was to pour hot coffee in a cool, glass mug. Quite a dangerous job, that was. I can’t tell you how many mugs have shattered in my hands… So make sure the jars are still hot when you fill them!

Once your jam (or syrup, or Crème de Cassis) is ready, get the hot glassware out of the hot water.

Getting the glassware out of the pan is always a bit tricky and can require some practice. I usually just fish the jars out using a pair of forks. As the jars don’t have long necks, they usually tip and empty as you lift them out of the water. Bottles, on the other hand, are a whole different ball game. Bottle game. Whatever…

Because of their height and necks, it can be difficult to tip them over and empty them. So, using a fork, I usually stand the bottles upright in the pan. This enables me to grab hold of them once I’ve put on a big, yet very clumsy oven mitt. Don’t be lured into a false sense of protection by the mitt though… Hot water will go right through it, so make sure you only touch the bottle.

Carefully empty the bottle into the pan.

Not too difficult or dangerous, right? Just remember to always be careful with hot water. Keep kids, pets and clumsy loved ones out of the kitchen!

Have a clean tea towel ready, and place the hot bottles and jars on top of it.

Then immediately fill them with hot jam or syrup. Don’t get distracted by long-distance phone calls or attractive delivery guys… And make sure to fill the jars and bottles all the way up to the rim.

Once the jars and bottles are filled, use a clean, damp cloth to clean the rims, don your trusty oven mitts again and screw on the lids.

Then leave the filled and sealed jars to cool upside down. This creates a vacuum, which, together with the proper sterilization of the glassware, ensures a long shelf life.

That’s it! That’s all there is to it.

Now start cooking up some jam, syrup or – if you like things fancy – Crème de Cassis!

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