I suggest you use each paper towel until it gets dark and starts smearing dust or until you move on to the next fan blade whichever comes first.
Black dust on fan blades.
Most of the dust particles that are floating in your house has some sort of electric charge which can often cause dust molecules to attract together hence the dust bunnies underneath your bed.
Additionally fan blades move rapidly through the air rubbing and brushing against air molecules and pushing them out of the way.
This same thing happens to the leading edges of your ceiling fan blades.
Stand on a step stool or ladder to reach the fan blades.
Over time a large volume of the circulating air hits and collects on the blades of the fan.
It may alternatively be due to soot produced from candles.
You don t want to lather it on but make sure it reaches every part of every blade.
Once they re all dry apply your paste car wax.
But they must understand that there is a lot of dust in the circulating air.
Next you re going to make sure that each blade is dry.
If the register is closed the air is forced along the ceiling and the next thing you know you ll start to see black buildup across your ceiling.
The air always has a great deal of dust in it larger particles that you can see and also microscopic ones.
People often ask why spider webs and dust can be seen on the fans.
Soot deposition is most likely to occur on wall and ceiling surfaces in rooms where candles are burnt.