Over the years there has been some discussion of the origin and nature of the "BLACK DUST" that occurs in, on and around our layouts. Very fine grained brass from the grinding of the metal wheels of the engine and cars on the edge of the tail head has been suggested as one source and carbon from the arching between wheels and rails of engines has also been suggested. Yesterday I started an experiment to determine the composition of the black dust. I polished the top of my mainline with a green Scotchbrite pad and I followed it with a wet sponge to remove any dust on the top or the inside of the railhead.
I ran two engines for 2.5 hours each. My Aristo Mallet with a battery pack and my LGB Sumpter Valley Mallet via track power. My SV Mallet along with my Uintah Mallet are always causing a lot of arching and are the only engines that really need wheel cleaning on a regular basis.
After each run I wiped the railhead and inside with an alcohol wipe. I also did a Scotchbrite pass and following that cleaned the rails with a rag. I could not pick up any black dust after the cleaning.
Here are some pictures of the wipes after each run. I'm going to take them in to a lab so see if we can analyze the black dust.
PS The curves on my layout are all 10' diameter Aristo wide radius.