Help in reading labels on ICs?

Once upon a time someone posted that they had found something that really 
brought out the numbers etc on otherwise difficult to read ICs. 
Unfortunately I didn't save the post, or the info in it.  Anybody have any

ideas on what this might have been, or how to read those invisible 
numbers/letters?  Some ICs are no problem, but others...  I am getting 
really tired of trying to get the light just right and halfway guessing at

what they say.

TIA,

Dave