What do they mean?
I'm reading a book called the complete illustrated guide to coin collecting. They say " generally speaking, a good decreasing solvent will work wonders in removing surface grime. A drop or two of good quality lighter fuel on the surface of the coin, gently wipe off with a very soft cloth, will remove all of or most of the dirt." Beforehand they are talking about human hands oil. My question is, what is lighter fuel? I found 3 different types listed in wikki.