Wash potatoes, then peel them and cut them into cubes no bigger than half an inch. Small potatoes (1-2 inches) can be left whole, but must be peeled.
As you peel and chop the potatoes, put the cubes into a big bowl or pot filled with water. This prevents them from changing colour and also drains a bit of the starch from the potatoes.
Boil water in a big pot. You'll be blanching the potatoes, so it should be big enough to accommodate all of the potatoes, or at least to accommodate batches of potatoes. Boil additional water, either in a pot or a kettle; this will be for adding to the jars with the potatoes.
While waiting for the pot of water to boil, rinse the potatoes once more to wash away more starch.
Boil potato cubes for two minutes. If using small whole potatoes, boil them for ten minutes.
Drain the potatoes.
Pack into pint or quart mason jars, leaving one inch of headspace. Add ½ teaspoon of salt to each jar. (Adding salt is optional, but potatoes can be very bland without added salt at this step and sometimes the blandness can't be remedied.)
Add boiled water, maintaining one inch of headspace. Debubble and top up water if needed. Wipe jar rims, put on lid and screw band to fingertip tightness.
Process in a pressure canner as per your pressure canner's directions. *See note below.Pressure gauge at 10 lbs, dial gauge at 11 lbs. Adjust as necessary based on your altitude.Process pints for 35 minutes, quarts for 40 minutes. When finished, bring canner pressure down as per canner instructions. Remove jars from canner and set on a heavy towel overnight to cool and seal. The next day, check that jars sealed; if any didn't seal, put them in the refrigerator and use them within a couple days.