Best Way to Store Jewellery to Prevent Tarnish "Anything silver or costume can tarnish, so it's better to keep those sealed away from air that can cause oxidisation. [They] could even be stored in the original packageing that it came with. Any sealed plastic bag [like] a Ziplock will do. If your jewellery gets tarnished, a quick swipe with toothpaste should clean it up nicely." — Maya Brenner