The kid in the family who owned this house before we bought it last year used to skateboard with his friends in front of the house. They used to grind along the curb and this has left a pretty thick layer of what appears to be curb wax smeared with metal deposits ground into the side of the curb.
It’s cool to play on, but it looks like hell. Anyone know how I can remove this deposit?
It’s not really a good idea to flush kerosene down the sewers.
There must be a better way.
Amway makes a very good “Concrete Cleaner” (or at least they did years ago when I last bought some). Unfortunately, in order to buy anything from Amway you have to locate one of their dealers and then listen to the multi-level marketing spiel.
Naphtha, available in quart and gallon cans at Ace Harware and Home Depot, etc. is cheap and effective on wax. After you loosen it, wipe on a little dish soap and use a scrub brush.
Anything permanent will go with paint stripper, which breaks down the wax rather than just dissolving it. But it requires gloves. Rinses clear with water and is not harmful to the environment once diluted.
For dull concrete, grey and black stains, and moss or mildew, use cheap bleach, just straight from the bottle. Be careful, as it will splash and put white spots or holes in your jeans. Once again, when diluted it is not a pollutant, but converts to harmless salt when dry.
Muriatic acid is a good general purpose cleaner for most all types of masonry products. Available darn near everywhere-Depot, perhaps K-Mart. Use with appropriate precautions.
HCl is a good general purpose concrete cleaner, but the halogen acids act only weakly on waxes. They are good at etching concrete, so I’d expect RumMonkey would end up with a patch of shiny etched clean curb, surrounding an ugly waxy mess.
If kerosene or naphtha are unacceptable solutions, you could try using one of the orange oil based cleaners. There’s dozens of brands that all seem about the same. The key wax dissolving ingredient is limonene.
You can try a paste of washing soda and water. Smear it on, let it sit away, and wipe off. Buy it in the laundry section.
If you can run enough extension cords, a hot blow dryer might melt it enough so you can wipe it up.
I bought a 40 buck handheld steam cleaner a while ago. They are advertised on TV here all the time for much more. I got mine at Aldi. It would eat your wax build up. It cleans everything - spray with orange oil based cleaner, leave while it heats up and a few blasts gets rid of anything so far. Great for the brakepad dust on the mag wheels.
I should add that it is sometimes a bit laborious and time consuming for big messes but it does work.
Wax burns right? Seems to me a little fire is called for! 
Pressure washer?
Wouldn’t soapy, warm water work just as well as anything else? All these inorganic solvents being suggested to clear off wax - the kerosene is a little closer but all you need is soap.
I was thinking pressure washer too. Admittedly I’ve never used mine (2650 psi) on “curb wax” but it shure took off everything else it encountered on the sidewalk and driveway, including 8 year old oil stains.