Fresh corn: husk and silk corn, then wash. Put the cobs in a large pot of water, bring to a boil and boil 3 minutes. Scrape kernels off going about 3/4 of the way down into the corn, without scraping the actual cob.
Frozen corn: If using frozen, empty bag into a large microwave-safe jug or bowl with approx 1 cup ( 8 oz / 250 ml) of water, cover and zap for 7 minutes. Drain well.
However you obtained the corn kernels, for each 500 g / 1 pound / 1 litre / 1 quart of corn kernels, put in a large pot with 250 ml (1 cup) of water. Bring to a boil, then lower to a simmer and let simmer for 5 minutes.
Pack loosely into half-litre (US pint) jars or 1 litre (US quart) jars.
Leave 3 cm (1 inch) headspace.
Top up with clean boiling water (such as from a kettle, for instance), maintaining headspace.
Debubble, adjust headspace.
Wipe jar rims.
Put lids on.
Processing pressure: 10 lbs (69 kPa) weighted gauge, 11 lbs (76 kpa) dial gauge (adjust pressure for your altitude when over 300 metres / 1000 feet)
Processing time: half-litre (US pint) jars for 55 minutes OR 1 litre (US quart) jars for 85 minutes.