pickled grapes with cinnamon and black pepper

INGREDIENTS

• 1 pound red or black grapes, preferably seedless
• 1 cup white wine vinegar
• 1 cup granulated sugar
• 1 1/2 teaspoons brown mustard seeds (hm, mine might have been yellow? I was unconcerned.)
• 1 teaspoon whole black peppercorns
• 1 (2 1/2-inch) cinnamon stick, cut in half (if using two jars, otherwise leave whole)
• 1/4 teaspoon salt