One strategy I have employed for paper wallets is this:
- Print key/qrcode/whatever
- Fold paper a few times so you can't see the info through the paper
- Put the folded paper in a envelope
- Laminate the envelope (water barrier)
- Put laminated paper in a fireproof chest (fire barrier 1)
- Put fireproof chest in fireproof safe (fire barrier 2)
Note: fireproof/waterproof chests are notorious for holding in moisture. If you do not laminate your paper backup you risk moldy paper. Either open your chest often to exchange air or use moisture absorbing tools.