Cleaning Track & Wheels Scientifically - Addendum 2025-07-13

That black gunk from nowhere that plagues model railroaders has finally been figured out. It is caused by micro-arching between the wheels of powered locomotives and the track on the inside of the track where the flange meets it. This is shown in fig. 1. 

Figure 1

Over time the gunk builds up on the wheels to the point that the locomotives run intermittently or just plain badly (or not at all). Then you have to clean the track and/or wheels and it seems as if we are always cleaning something.

The author’s background is in Chemistry and he understands that in order to prevent the gunk in the first place you have to prevent the micro-arching. The only way to do this is to clean the track and wheels with a liquid that has a low dielectric constant meaning it is a non-polar solvent. You don’t really need to understand what that is. All you really need to know is that lower dielectric constants prevent arching and which solvents have a low dielectric constant.

The table on the left (thanks to Model Railroad Hobbyist Magazine) is a list of many solvents that most readers should be familiar with. The key to this table is that the solvents are listed from the lowest dielectric constant to the highest.

So what solvent is the most commonly used by model railroaders that have never heard of dielectric constants? Would you believe Isopropyl alcohol? Look at table 1 and find Isopropyl alcohol (commonly known as IPA). What is its constant? How good do you really think it is at keeping track clean? Are you still cleaning a lot?

There are some solvents to definitely not use (common sense) Kerosene, Gasoline (explosive), Carbon Tetrachloride (carcinogenic) are just some of them. Mineral Spirits is a good choice because of both its low dielectric constant and its cost. It also comes in an odorless form.

The author has tested several of the low constant solvents on his home layout with these results.

WD-40 contact cleaner - inexpensive but dries much too quickly making it difficult to clean engine wheels. Also recommends good ventilation (toxic).

CRC contact cleaner - Plastic safe but expensive and has multiple warnings of highly flammable spray.Also dries too quickly.

Gasoline, Kerosene & Diesel - forget it (you figure it out)!

Mineral Spirits (odorless) - inexpensive and readily available. The author is currently testing this on his home layout.

By the way, he has also gotten rid of his IPA except when laying ballast.

Addendum 2025-07-13
There has been some pushback concerning the use of oderless mineral spirits for cleaning track and wheels. Along with these arguments against its use is the author's response. Do your research first before spouting off that you know better.

IT'S FLAMMABLE
The flashpoint (the temperature at which a substance will easily ignite if exposed to a spark or flame at or above this temperature) of Isopropyl Alcohol is 64 - 75 degrees F  while the flashpoint of oderless mineral spirits is 100 - 140 degrees F. Which do you think will flash first?

IT DAMAGES THE PLASTIC OF LOCOMOTIVES
What are you doing, putting it on with an air brush? Use common sense. To clean track put it on a small felt pad and clean it. For locomotives the author removes some sheets from a alcohol wipes container, let's it dry out in open air and then puts OMS on it on a test track and runs a locomotive, holding it still, to clean it's wheels. It's not that difficult to figure out.

IT DAMAGES SCENERY
See the above remark.

As the author said above, it not difficult to use, it's not dangerous, it not damaging (common sense, remember?) and it cleans better.

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