How to Sterilise Jars and Bottles

Glass jars drying on a clean cloth after sterilisation

How to Sterilise Jars and Bottles

Sterilising is the step that many people skip, assuming a good wash with hot soapy water is enough. It is not. Any bacteria, yeast or mould left inside a glass jar or bottle will compromise the preserve, shorten its shelf life and, in more serious cases, pose a genuine food safety risk. Whether you are making jam, cordial, flavoured vinegar or chutney, spending ten minutes on proper sterilisation is the difference between a product that lasts months and one that spoils in weeks.

This guide covers every available method, when to use each one and the most common mistakes to avoid.

Before You Start: What to Check

Before sterilising any glass container, check its condition carefully. A jar or bottle with even a small chip, crack or irregular rim should be discarded. The heat of the oven or boiling water can cause already compromised glass to fail, and even a hairline crack on the rim will prevent the lid from forming a proper airtight seal.

Always check:

The rim of the neck (even minor chips will prevent a reliable seal)
The base and sides (surface cracks that become fractures under heat)
The condition of the lids: dry, rusty or deformed seals will not close correctly and must be replaced

Wash jars and bottles with hot soapy water before using any sterilisation method. Sterilisation kills microorganisms but does not remove food residue or grease

Method 1: Oven

Glass jars placed upside down in a hot oven for sterilisation

The oven method is the most convenient way to sterilise several jars at once and is best suited to preparations that are filled while hot, such as jams, chutneys and preserves.

How to do it:

Preheat the oven to 140°C (conventional heat, not fan).
Place the clean jars upside down directly on the oven rack or on a baking tray. Inverting them prevents any residual moisture from collecting inside.
Leave in the oven for 15 minutes.
Keep the jars warm in the oven until you are ready to fill them. A cold jar filled with boiling hot preserve can crack from the sudden change in temperature.

Lids must never go in the oven. The dry heat deteriorates the inner seal of screw caps and twist-off lids. Lids should always be sterilised separately in boiling water (see Method 2).

Suitable for: jars of any size, hot-fill preparations.

Not suitable for: tall narrow bottles (difficult to stand upside down safely), lids and caps.

Method 2: Boiling Water

Several glass jars submerged in a large pot of boiling water

The boiling water method works for both jars and bottles and, most importantly, it is the only method suitable for sterilising lids and caps. It is also the correct method when you want to process already-filled jars to extend shelf life (water bath canning).

How to sterilise jars and bottles:

Place the jars or bottles in a large saucepan. Cover completely with cold water.
Bring to the boil and maintain a full boil for 10 minutes.
Remove with kitchen tongs and leave to drain upside down on a clean cloth.
Use while still warm. Do not allow them to cool completely before filling.

How to sterilise lids:

Submerge lids in boiling water for 5 minutes.
Remove with tongs and drain on a clean cloth.
Do not dry with a tea towel, as this reintroduces bacteria onto the surface.

Suitable for: jars, bottles, screw-top lids, metal caps, rubber seals for clip-top lids.

Method 3: Dishwasher

Clean empty glass jars loaded into a dishwasher for high-temperature cleaning

A dishwasher can sterilise effectively if it reaches a high enough temperature, specifically at least 60°C during the wash cycle. Most modern domestic dishwashers have a programme at 65 or 70°C which is adequate.

How to do it:

Load the jars or bottles into the dishwasher, empty and open.
Select the hottest programme available, without detergent.
Use the jars immediately after the cycle while they are still hot.

Important limitations:

The dishwasher method is not recommended for sterilising lids and caps, as high temperature programmes can deteriorate the inner seals. Lids should always be sterilised in boiling water.

This method is practical but less reliable than the oven or boiling water, because the actual temperature reached inside the jars can vary. For long-life preserves or low-acid products, the oven or boiling water method is preferable.

Suitable for: jams, cordials, vinegars, high-acid products.

Not suitable for: low-acid preserves, products with a shelf life of more than 6 months.

How Long Do Sterilised Jars Stay Sterile?

A sterilised jar does not stay sterile indefinitely. Once removed from the oven or boiling water, it should be filled within 30 minutes. Left open to the air for longer, it progressively recontaminates from bacteria and yeast present in the environment.

If you are preparing large quantities and cannot fill all the jars quickly enough, sterilise in batches rather than leaving jars standing open for too long.

Common Mistakes to Avoid

Filling a cold jar with boiling hot preserve. The sudden temperature change can crack the glass. Jars must be warm at the point of filling, not cold.

Putting lids in the oven. Dry heat deteriorates the inner seal and the lid will no longer close correctly. Lids should always be sterilised in boiling water.

Drying with a tea towel. Even a clean tea towel reintroduces bacteria onto the glass surface. Leave jars to drain upside down on a cloth and do not touch the inside before filling.

Reusing twist-off lids more than once for heat-processed preserves. The inner seal compresses on first use and cannot reliably re-seal if used again for hot-fill or water bath processing. It can be reused as a simple closure for refrigerator storage, but not for long-term preservation.

Using recycled commercial jars (pasta sauce jars, yoghurt pots and similar) for long-life preserves. These containers are not designed to withstand repeated heat cycles and their seals do not offer the same reliability as jars made specifically for home preserving.

Ready to Start Preserving?

Now that your sterilisation is sorted, ensure your preserves stay safe and delicious for longer. Using the right containers is essential for successful home preservation.

Discover our professional-quality glass jars and bottles, specifically designed to keep your jams, chutneys, and creations fresh and perfectly sealed.

Shop Jars & Bottles

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