The Complete Guide to Canning at Home

A variety of premium glass canning jars filled with preserved vegetables for home food preservation.

The Complete Guide to Canning at Home

Canning is the art of heat-processing food in sealed glass jars to create a shelf-stable product that can last 12–18 months without refrigeration. It’s an essential skill for anyone serious about home food preservation — and it’s simpler than most beginners assume.

The Two Methods of Canning

Water-Bath Canning (Boiling Water Canning)

Used for: high-acid foods (pH below 4.6) Examples: jams, jellies, marmalades, pickles, fruit preserves, tomatoes (with added lemon juice), chutneys

Water-Bath Canning involves submerging sealed jars in boiling water (100°C) for a set amount of time. The heat kills spoilage organisms and drives out air, creating a vacuum seal as the jars cool.

Equipment needed:

Large stockpot or dedicated water-bath canner (deep enough to submerge jars by at least 2.5cm)
Jar rack to keep jars off the bottom of the pot
Jar lifter
Wide-mouth funnel
Lid wand (magnetic, for handling flat disc lids)
Timer

Pressure Canning

Used for: low-acid foods (pH above 4.6) Examples: green beans, carrots, potatoes, meat, fish, soups, stews

Low-acid foods cannot be made safe by boiling water alone. The temperature required to destroy Clostridium botulinum spores (121°C / 250°F) is only achievable under pressure. Pressure canning is the only safe method for these foods. Do not attempt to water-bath can low-acid foods. This is a serious food safety risk.

Step-by-Step: Water-Bath Canning

Sterilise jars. Wash in hot soapy water, then heat in the oven at 140°C for 15 minutes.
Prepare your recipe. Make your jam, pickle or preserve as normal.
Fill jars. Leave the correct headspace (usually 5-10mm). Remove air bubbles with a skewer.
Wipe rims. Any residue on the jar rim will prevent a proper seal.
Apply lids. Place flat disc lids and screw bands to fingertip tightness - not over-tight.
Process. Lower jars into boiling water, ensuring full submersion. Process for the time specified in your recipe.
Cool. Remove jars and set on a cloth-covered surface. Do not tilt or move for 12-24 hours.
Check seals. Press the centre of each lid. If it flexes up and down, the jar has not sealed - refrigerate and use within a week. A sealed lid is firm and concave.

Headspace: Why It Matters

Jams and jellies: 5mm

Pickles and relishes: 10mm

Whole fruits and tomatoes: 12mm

Low-acid vegetables: 25mm

Too little headspace causes food to boil out and prevents a seal. Too much leaves excess air that can cause discolouration.

Choosing Jars for Canning

For water-bath canning, use only jars specifically designed and tested for heat processing. Key specifications:

Tempered glass - designed to withstand thermal shock
Standard neck sizes - compatible with replacement lids (70mm or 86mm diameter)
Unchipped, uncracked - any damage risks cracking under heat or compromising the seal

Shelf Life and Storage

Properly processed, sealed jars: 12-18 months in a cool, dark place
After opening: refrigerate and use within 4 weeks
Any jar with a bulging lid, spurting liquid or off smell should be discarded without tasting

Common Canning Mistakes

Under-processing: This can lead to seal failure or spoilage. Always ensure you follow tested recipes and boiling times.

Skipping sterilisation: This creates a high risk of contamination. Always sterilise all jars and lids before filling.

Loose lids: If lids aren't tightened correctly, you won't get a vacuum seal. Remember to fingertip-tighten them firmly but without forcing.

Reusing commercial lids: Most commercial lids are designed for single use. For the best results, always use new twist-off lids for each batch.

Cold jars: Filling cold jars with hot jam causes thermal shock. Keep your jars warm in the oven until the moment you fill them.

Start Your Preservation Journey

Precision is the secret to perfect canning. By following these safety standards and using professional-grade jars, you can preserve the best of the season for the entire year. Explore our collection to find the perfect fit for your pantry.

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