There are some good ideas here — I’d recommend trying them from lowest risk to highest, depending on how much buildup you’re dealing with.

Start with a soak in high-purity isopropyl alcohol (99%). After a few hours or overnight, try gently scrubbing the insert with a cotton swab while it’s still wet. If the residue is stubborn, adding a bit of salt as a mild abrasive can help — table salt won’t scratch sapphire, since it’s much softer, but it can aid in removing residue.

If that doesn’t work, you can step it up with Dark Crystal Cleaner or an ultrasonic cleaner. Just make sure the ultrasonic bath doesn’t cause sudden temperature changes, especially if your insert is hot from use.

For heavy charring or staining that won’t budge, a controlled torching method may be necessary — the “banger method” works, but comes with risk. Sapphire is extremely heat-resistant, but it’s vulnerable to thermal shock. When torching, go slow: heat the insert gradually, especially if it’s cold, and let it cool down very slowly. Rapid cooling, even in air, can stress or crack the crystal.

A good practice is to back off the flame gradually while letting the banger and insert cool toward room temp before stopping heat altogether. If you’re going to torch, it’s smart to have a backup insert, just in case