It was well used when abandoned, and sat, unused, for four months, and it looked REALLY dirty. What a perfect opportunity to test track cleaning methods, if needed, to destruction.
I took out my voltage testing car. Folks will want to see it (below). Yes, its not pretty, but its effective: a lighted caboose chassis with a digital voltmeter and two 12-watt at 12 volt lights to create a load so I test voltage under a load approximating a loco. The copper sheet is a lampshade so the lights don’t shine in my eyes and make it difficult to read the voltmeter. You can see, its registering 10 volts now.
Anyway, the track is fed at both ends by #10 wire leads (of about 25 - 30 feet length) and I set the transformer (a Z4000) to an indicated 12 volts.
I tested the track under the numbered conditions below of increasingly harsh cleaning, drying and dusting the track thoroughly each time before testing the voltage. I also examined the track surface for damage by the cleaning method with a jeweler’s loop at each stage, and I will comment later on that.
First the voltage tests.
1. Uncleaned track – voltage 5.7 to 7.4 volts. Geeeeezzz! No wonder dirty track is always the first gremlin suspected when there are electrical problems! That is some voltage loss just due to dirt and grime. I would not have believed it if I had not seen it.
2. Isopropyl alcohol on a cleaning pad (denim cut from old pair of jeans) rubbed back and forth several times along the track: 6.7 to 8.5 volts.
3. More of the same, harder: 8.2 to 9.0 volts
4. More of the same, harder still: 8.5 to 9.0 volts
5. More of the same, harder still, much longer: 8.5 to 9.0 (no change)
6. Track cleaning tool (hard rubber or something, bought it at LHS) rubbed back and forth on the track: 8.8 to 9.2 volts
7. Fine steel wool, rubbed up and down the track surface several times, pressing hard: I could see the track surface glean more as I rubbed: 9.6 to 10.3 volts. I should add that if you ever do this it is recommended: a) power down the track first (although the results of steel wool across the track when it is at 12 volts are, ah, interesting), b) then go over the track with a powerful magnet before using it again (I used a 2” 100 lb neodymium magnet): it picks up an amazing amount of tiny metal debris from the steel wool.
8. Number 2000 wet dry sandpaper, dry: 9.8 to 10.3 volts (no change)
9. Number 1000: 9.8 to 10.3 (no change)
10. Number 600: 10.2 to 10.8
11. Number 320: 10.2 to 10.8 (no change)
12. Number 150: 10.2 to 10.8 (no change although the track is obviously scarred and pitted)
13. New track taken from sealed package and looking very shiny. 10.2 to 10.8 (no change).
Okay, so apparently I had a bit more than a volt of drop across the leads to the track and/or in the connections thereto and/or between the wheels and the track surface. Reasonable altogether, I guess.
Anyway, under a jewelers loop, the surface of the new track looks smooth and perfect. By contrast, used track anywhere on my layout, including this three year old section of test track before I started, looked badly scratched up: I conclude that use alone leaves a rough sratched surface under magnification. But nothing until the 320 sandpaper made it scratchier, although the 600 might have made it just a bit worse – couldn’t really tell though.
My conclusion, frankly, is that fine steel wool or around #800 wet dry sandpaper used with discretion might be the nuclear weopon of track cleaning. I intent to use the steel wool and #800 if and when things get bad, but stick to alcohol and the track cleaning eraser otherwise.
anyway, it was a fun afternoon and I learned something: keep the track clean.
Steel wool? 
I run around with a voltmeter and just measure, you have it automated.
