Toss the cucumbers and onion with the salt, cover them with the ice, and let them stand for 30 minutes.
Drain the vegetables, rinse them under cold water, and drain thoroughly again.
Bring the vinegar, sugar, mustard seeds, celery seeds, turmeric and cloves to a boil for 2 minutes until the sugar dissolves.
Pack the cucumbers and onions into three clean 1-pint jars and pour the hot brine over them, leaving 1/2 inch of space.
Cool for 30 minutes, cover, and refrigerate for at least 24 hours before eating and for no longer than 1 month.