Spread a kitchen towel on the counter. Use your jar lifter to remove a warm jar from the canner, drain it, and place it on the towel. Keep the remaining jars in the canner so they stay warm.
Use your canning funnel and ladle to fill the jar with the relish leaving 1/2-inch headspace.
Run the bubble popper through the jars to release air bubbles and wipe the rims. Adjust the headspace again if needed.
Center a lid on the jar, and screw on the band until it is fingertip tight. Use the jar lifter to place the jar back into the canner, and repeat with the remaining jars.
Once all the jars are in the canner, adjust the water level so it is 2 inches above the jar tops.
Cover the canner and bring it to boil over high heat. Once the water boils vigorously, continue boiling and process the relish for 10 minutes at altitudes of less than 1,000 feet. Adjust processing time for your altitude if necessary (See Notes).
When the processing time is complete, turn off the heat, remove the cover, and allow the canner to cool down and settle for about 5 minutes.
Spread a dry kitchen towel on the counter. Remove the cover by tilting the lid away from you so that steam does not burn your face.
Use the jar lifter to remove the jars from the canner and place them on the towel. Keep the jars upright, and don't tighten bands or check the seals yet. Let the jars sit undisturbed for 12 to 24 hours to cool.
After 12 to 24 hours, check to be sure jar lids have sealed by pushing on the center button on the cover. The lid should not pop up. If the lid flexes up and down, it did not seal. Refrigerate the jar and use up within a week.
Remove the screw-on bands and wash the jars to remove any residue. Then label, date, and store them in a cool, dark location. Allow 4 weeks for the piccalilli relish to develop flavor. Use home canned jars within 12 to 18 months for the best quality. Makes about 6 half-pint jars of piccalilli.