How To Sterilise and Seal Glass Jars (2024)

Jams, marmalades and preserves should be added to sterilised jars and sealed while still hot. Your glass storage jars must be without chips or cracks. Just before use, they need to be sterilised and dried, using clean hands. Hygiene is important so use clean tea-towels when holding or moving the jars.

To sterilise jars

  • Place the cleaned jars on their sides in a large boiler or saucepan; cover with cold water.

  • Cover the pan and bring to the boil over high heat; boil for 20 minutes.

  • Carefully remove jars from water; drain.

  • Stand, top-side up, on a wooden board. The heat from the jars will cause any remaining water to evaporate quickly.

  • Stand the clean jars, top-side up, on a wooden board placed in a cold oven (do not allow the jars to touch); heat oven temperature to very slow (120°C/100°C fan-forced), then leave the jars in the oven for 30 minutes.

How To Sterilise and Seal Glass Jars (1)

To seal jars

As soon as the preserves are spooned or poured into the sterilised jars or bottles, they must be correctly sealed to prevent deterioration. Fill the hot dry jars right to the top – preserves shrink slightly on cooling and a full jar means less trapped condensation. Seal the jars while still hot. This rule applies to all jams, jellies, pickles and chutneys.

Which lid do I use?

  • Metal lids are not suitable unless they have a protective plastic insert or liner to prevent corrosion.

  • Plastic screw-top lids give a good seal (plastic snap-on lids are not airtight enough). Plastic lids must be well washed, rinsed and dried, or put through the dishwasher.

  • Some older preserving outfits have glass lids; these can be sterilised in the same way as the jars.

  • Do not use aluminium foil, cellophane or paper covers for preserves; acid in the preserves will corrode foil, while paper and cellophane are not airtight enough for long-term keeping.

How To Sterilise and Seal Glass Jars (2)

Paraffin wax

To seal jars the old-fashioned way with paraffin wax (available from chemists):

Where can I find a “cool dark place”?

Most modern homes have heating in every room, so if a recipe tells you to “store in a cool dark place” consider the garage, cellar or under the house where it’s cool and the temperature is constant. If you live in a wet or humid climate, then use the refrigerator.

For some brilliant jams, conserves and chutney recipes, check these out:

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How To Sterilise and Seal Glass Jars (3)

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How To Sterilise and Seal Glass Jars (2024)

FAQs

How To Sterilise and Seal Glass Jars? ›

Basic process for sterilising jars

How do you sterilize and seal jars? ›

Wash your jars and the lids in hot soapy water, but do not dry them. Instead, leave them to stand upside down on a roasting tray while they're still wet. Pop the tray of clean, wet jars and lids in to a preheated oven at 160-180ºC for about 15 mins.

How do you sterilize glass jars without breaking them? ›

Oven Method Sterilization

Preheat your oven to 275 degrees. Wash each canning jar or mason jar and lid with hot soapy water then rinse but don't dry them. Place each clean jar on a baking tray and place in the oven for 10 minutes.

How long do glass jars need to be sterilized? ›

To sterilize empty jars, put them right side up on the rack in a boiling-water canner. Fill the canner and jars with hot (not boiling) water to 1 inch above the tops of the jars. Boil 10 minutes at elevations of less than 1,000 ft. At higher elevations, boil 1 additional minute for each additional 1,000 ft.

How long do you boil jars to seal them? ›

Bring to a rolling boil, cover the canner and boil for 10 minutes if using 4-, 8- or 12-ounce jars or for 15 minutes if using 16-ounce jars. (Check individual preserve recipes for more specific processing times.) Let cool for 10 minutes before removing the jars from the pot.

How to make a glass jar airtight? ›

- Use a mason jar and ring lid. The ring lid forms a good seal that pulls down tight under suction pressure to close the jar. - Use a jar with a screw-top lid fitted with an elastomeric or rubber seal ring around the lip. When you screw on the ring, it compresses to form an airtight seal.

How to seal glass jars at home without a canner? ›

Mason jars are made for canning food. You don't want that food to spoil. You seal the jar by sterilizing the jar, and by putting hot food in it and putting the seal on, then screw the lid on. As the contents cool, the air inside will contract causing the lid to seal tight.

How do factories seal jars? ›

A vacuum seal occurs when heat applied to the contents during processing causes contents to expand and drives air from the jar. During processing, heated air escapes from under the lid creating a vacuum. As the jar cools, the lid contracts and a seal is formed.

What happens if you don't sterilise jars? ›

What Happens If You Don't Sterilise Jam Jars? Sterilising your jars removes any potential bacteria that may be harbouring inside. Even if your jar looks clean, always sterilise before use to stop your homemade preserves from spoiling. Sterilising your jars expands the shelf life of the preserve too.

How hot does water need to be to sterilize glass jars? ›

Place jars and lids in a deep saucepan over high heat. Cover with cold water. Bring to the boil. Reduce heat to medium and boil for 10 minutes.

Can you sterilize jars in the dishwasher? ›

The dishwasher method is a good method for sterilizing your jars good if you have a high-temperature setting on your machine or a steam dishwasher. Fill your dishwasher with clean cold jars and run a minimum or rinse wash to time the ending with when your jam, preserve or pickle will be ready.

How do you sterilize canning lids and rings? ›

Wash the jars, lids and bands in hot, soapy water; rinse well. Put the jars on a rack in a pot of water. Boil 10 minutes, then reduce the heat and simmer until ready to use. Meanwhile, put the lids and bands in a separate saucepan of simmering water until ready to use (do not boil).

How to seal canning jars without boiling? ›

Will canning jars seal without boiling? The simple answer is, yes. A jar will sometimes even seal itself, if you put hot food and a lid on it. There was a “new” jam and jelly processing method circulating, a number of years ago, wherein hot jars were filled with hot jam/jelly, and lids and rings were put on the jars.

Can you sterilise jars in the microwave? ›

Sterilising in the microwave

For a small number of jars, this can be a handy way of sterilising. Wash jars and rinse them before standing them upright in your microwave and microwaving them on full power for 60 seconds. Lids can be sterilising by submerging them in a pan of boiling water for 10 minutes.

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