Removing tear patina from granite edge - how?

Hello,

I have 40 granite curbstones here that come from road construction and I would like to install them.

Unfortunately, over the years a very thin tar patina from traffic has formed in some places. How can I remove it?

The surface of the stone is very rough. I can’t get anywhere with solvent and scrubbing.

Thanks in advance

So I have no practical experience, but try hot [Margerine]. Theoretically, it should work.

And then? Scrub with that? But then I have a huge grease stain that soaks into the stone.

Yes, scrub off. Well, the grease might be more even and less noticeable in the end, sooner or later it will wash out anyway... I don't know what you want to do with the stones. You can also try [Waschbenzin] and warm the stones first with a heat gun. Your "tar" (I rather assume it is bitumen, tar has not been allowed to be used in road construction for a very long time) is a hydrocarbon that was heated during processing. So you also need heat (warmth) and another hydrocarbon, which is preferably not sticky, to remove it. That's how I came to the theoretical basis. Maybe try it on one stone first...

Ah ok. How about petrol and brush then?

My approach would be sanding - of course, the rough structure will not be preserved in the process.