• Cosy Cookhouse Team


Updated: Aug 29, 2019

We received several requests from our customers asking us how to properly do canning at home, and what tips can we share from our experience of making fruit spreads as our side business for over 4 years now. So, we decided to make a 'how to properly cook and can fruit jams' series, from start to finish. We'll explain each step in depth with easy to follow instructions and share with you all our tips and tricks for creating the perfect fruit jam right from the comforts of your kitchen in the following months. For this month, we will start by looking into sterilizing the glass jars.

Why Sterilize

To begin with, why would you want to sterilize jars for all your lovely preserves? The reason is simple. Because a clean sterilized jar is essential to the success and longevity of the fruit jams and preserves you spend a lot of time making. Sterilizing is a crucial part of preserving to remove any bacteria, yeasts or fungi thus protecting the food you put into the jar. Dirty jars which are not correctly cleaned will infect the food inside, causing it to spoil very quickly. 

Sterilizing is an essential step, and thus should never be omitted. Plus, it is a quick and easy process.

Us Sterilizing in Action

Stetilizing Methods

There are 4 main ways to sterilize jars:

  • Boiling Water Canner

  • Microwave

  • Dishwasher

  • Oven

In our humble opinion based on experience, using the microwave, dishwasher or oven method is alright for making small quantities, say 20 jars. But if you are making a larger quantity (think 40 or more) for a special occasion, it may cause your electricity or water bill to sky rocket.

Our preferred method is the boiling water canner method. That being said, we're gonna dive into details using this method for this article.

What You'll Need

If you have a home canning kit, the boiling water canning container can be used to sterilize the jars. If you don't have a home canning kit, you will need a few items to complete the sterilization process, including: 

  • Glass canning jars

  • Boiling water canner or large pot with a rack

  • Jar lifter or kitchen tongs

  • Heat gloves (for extra safety)

The canning jars should be made of tempered glass with a two-piece vacuum cap (the metal screw band and flat, rubber-lined metal lid). If you are using a large pot, it needs to be at least two inches taller than the jars and should be fitted with a rack and a lid. 

Note: Do not sterilize the glass jars with the lid on. Sterilize them separately. The extreme heat of boiling water can harm the rubber sealing rings on the lids, which can result in a broken seal and contamination of the jar's contents. Read on for more info.

Adapting to Altitude

Submersing glass jars in boiling water is the standard method for sterilization, but altitude affects the temperature at which water boils. Higher altitudes lower the boiling point of water. For this reason, you'll need to adjust the time the glass jars spend in boiling water if you live at a higher altitude. The baseline boiling time is 10 minutes, but you'll need to add one additional minute of boiling time for each 1,000-ft. increase in elevation: 

  • Sea level to 1,000 ft: 10 minutes

  • 1,000 to 2,000 feet: 11 minutes

  • 2,000 to 3,000 feet: 12 minutes

  • 3,000 to 4,000 feet. 13 minutes

  • 4,000 to 5,000 feet: 14 minutes

  • 5,000 to 6,000 feet: 15 minutes

  • 6,000 to 7,000 feet: 16 minutes

How to Properly Sterilize Glass Jars

Once you have all of your equipment in place, the actually sterilizing should take about 25 minutes or so. 

Place the empty jars right-side-up in the boiling water canner or large pot. You may use the same pot for the boiling water bath when you fill the jars with food to preserve. Completely cover the jars with hot (but not boiling) water—the water should be one inch above the top of the jars. Bring the water to a boil over high heat. Once the water reaches a full rolling boil, begin timing. Boil the jars according to the time suggested above for the altitude. At sea level, for example, boil the jars for at least 10 minutes.

Turn off the heat. If you are not quite ready to begin the canning recipe, you can leave them in the hot water for up to one hour. If you are ready to remove the jars, do remember to wear heat gloves before starting. Accidents can happen anytime. If the water is still hot, and you accidentally drop the jar back into the water while removing it using a jar lifter or tongs, the hot water might splash upwards and burn your skin (a lesson we learned the hard way).

As you're removing the jars with a tong or jar lifter, drain well, and set aside to dry on a clean surface.

Warning: Sterilizing your jars will be quite pointless if the surrounding area is not perfectly clean. Your clean jars can easily pick up bacteria from surrounding areas that are contaminated. If you are setting your jars on dish towels to dry, make sure they are fresh and clean. Whenever possible, proceed to can immediately upon finishing the sterilization of the jars. If you wait more than one hour, you should resterilize the jars before starting the cooking and canning process. 

Cleaning the Lids and Rings

Most experts suggest that you simply place the canning lids and their rings into water that is simmering, but not boiling for about 10 minutes to thoroughly clean them. You can use the same water that was used to boil the jars once it has cooled slightly.

Always follow the manufacturer's recommendations. Some may specifically call for different methods for handling the lids and rings. 

Ta-da! Now you have clean, well sterilized glass jars and lids ready for you to use. Time to put on your chef apron and start cooking some yummy fruit jams 😋

Now we'd love to hear from you. Which method of sterilizing glass jars do you prefer and why? Also, what type of preserve or fruit jam do you like to make at home? Do share with us in the comments below.

Hope this helps, and we're so glad you're here. Thank you so much for reading 💚Do let us know how your sterilizing process goes 😉

Enjoy your day!


Trish & Björn

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