Drain well, rinse, drain again, rinse again.
Add the relish to a large-enough pot and add the vinegar, the celery seed, the turmeric, the mustard seed, and the sugar. Bring to a boil and then reduce to a simmer.
Add the corn-starch to the cold water, mix with a fork, and set aside
Meanwhile, turn your oven to 275℉.
Wash and rinse well the jars. Put the jars rim up on a sheet pan and pop into the heated oven for 10 minutes.
Turn oven down to 200℉.
Add the rings and lids to a saucepan, cover with water, and put in the oven.
When the relish has been simmering for about 30 minutes, check and adjust the seasonings. Might want to add black pepper. Or more peppers. Your call.
Add the corn-starch slurry and stir in well with a fork. Allow to thicken. This could take another 30-40 minutes.
Fill each jar with the relish to within ½" of the top, wipe the edge, add a hot lid, add a ring.
Add as many jars as will fit in your canner in a batch and boil for 5-8 minutes. Remove and set aside to cool.