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?

How To Sterilise and Seal Glass Jars (2)

Paraffin wax

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

  • Melt wax slowly in a small saucepan over low heat. It is important not to overheat the wax or it will shrink on cooling, giving an imperfect seal.

  • Pour a thin layer over the top of the cooled preserve, about 2mm thick, just enough to cover the surface. Leave until almost set, then pour another thin layer on top of the first layer.

  • Insert small pieces of string in the wax just before it sets to make it easier to remove wax.

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 (2024)

FAQs

How To Sterilise and Seal Glass Jars? ›

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 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 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 to sterilize glass 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.

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 do I make sure my jars seal? ›

Place lids on jars, screw on rings and lower jars back into the pot of boiling water. The water should cover the jars; if not, add more. Boil jars for 10 minutes. Transfer jars to a folded towel and allow to cool for 12 hours; you should hear them making a pinging sound as they seal.

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.

What happens if you don't sterilize jars before canning? ›

Dirty or jars not correctly cleaned will infect the food inside, and it will spoil very quickly. Sterilizing is a quick and easy process so therefore should never be omitted. Here are simple ways to achieve proper sterilization and make all your efforts at jam making, bottling and canning a success.

How do you sterilise jars quickly? ›

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.

Why do you turn jars upside down when canning? ›

Inversion Canning

Once secured, the jar is inverted (flipped upside down) and left to cool for several minutes before placed right side up. The thought behind the method is the hot food will sterilize the seal while creating a vacuum by allowing air to escape.

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.

What happens if jars don't seal? ›

If a jar does not seal and you did not follow safe processing methods, such as incorrect processing time, initial temperature (hot pack versus raw pack, initial temperature of the water in canner) was not observed, or the incorrect processing method was used, food can be re-canned within 2-hours.

How do you clean and sanitize 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.

Does boiling water sterilize jars? ›

Step 4 - Sterilise Your Jars With Boiling Water

Fill the pan with cold water until the jars are covered. Bring to the boil and keep at the maximum temperature for 10 minutes, turn the heat off and cover the pan to keep the jars warm until you are ready to fill them.

Are all glass jars microwave safe? ›

Yes, you can microwave most glass items as long as they are labeled “microwave safe”. Kitchen wares, such as glass items, that have the “microwave safe” label are made of materials that are safe to be used in the microwave.

Do I need to sterilize canning jars and lids? ›

Jars do not need to be sterilized before canning if they will be filled with food and processed in a boiling water bath canner for 10 minutes or more or if they will be processed in a pressure canner. Filled jars that will be processed in a boiling water bath canner for less than 10 minutes need to be sterilized first.

Do you put lids on jars when jam is hot? ›

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.

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