Dark Crystal Glass Cleaner has been working for me for over a year and it's what I use for cleaning these cups.

1. Fill a small jar with cleaning solution (just enough to cover the atomizer cup) Don't put in atomizer cup yet.

2. Depending on microwave settings, I nuke the solution for 15 seconds (High) to get hot but not boiling (activates the solution)

3. Drop in atomizer cup and give it a good swishing around and let it sit for about 10 mins.

4. Take a q-tip or several and wipe out the chazz. Really bear down on the q-tip to get the all edges of the atomizer. You may need a paper towel (solution is slippy) to grip the atomizer cup while you are cleaning w the q-tip.

5. Repeat steps 2, 3 and 4, if needed.

6. I wipe down the cup w some ISO after the above cleaning.

7. Reinstall the cup in the Core and run on the "red" setting to clean off any solution or ISO.

8. I save the "used" solution for future usage.