I picked up some dilapidated postwar American Flyer wheels at the local train store this afternoon to fix up some stuff from my junk box. The wheels were covered in milky white goo/powder/gunk/residue/stuff–whatever you want to call it. Almost anything molded of black plastic–wheels, couplers, truck sides–by Lionel or American Flyer in the 1940s and 1950s is prone to this. Fortunately, the fix is easy. Aim a hair dryer on high at it, and watch the whiteness melt away, leaving clean plastic behind.
I’ve heard several theories as to what this stuff is. I’ve heard it might be a chemical leeching out of the plastic parts, or that it might be the mold release, likely stearic acid. That’s a waxy lubricant sprayed on plastic molds so the plastic parts will pop out after they solidify, not the stuff that grows on bread. Don’t worry, your trains aren’t getting moldy. I suppose it could also be the combination of the two things reacting. I’m not sure anyone knows why heat from a hair dryer makes the white discoloration go away either. But it’s effective. I’ve never seen it come back, but if it does, just give it another round with the hair dryer.
But at any rate, that’s the quick and simple and cheap fix. Sometimes it takes five seconds, and sometimes it takes more like 30.
My Dad’s Lionel cars–his Scouts in particular–had discolored trucks and couplers. When I was growing up, I thought that was what they were supposed to look like, though I thought it was strange that half his cars had spotty white trucks and couplers and half of them had blackened metal trucks and couplers. I gave them the hair dryer treatment seven or eight years ago and they’ve looked right ever since.