Brake blocks that do not leave a residue?

[yenrod]

A mate paid bigtime for some cerimc rims and used the blocks but the braking is not sharp. You get a bit of residue but not as much as you are getting.

 

[Fab Foodie]

I find Shiomano brake pads over aggressive to the rims as they do seem to produce copious quantities of grey sludge. I changed to KoolStop salmons for all weather riding. They are a tad softer and so wear more quickly, but then I'd rather replace the pads than the rims.

Agreed.
Also changed from Ultegra pads to Koolstop Salmons (Fronts) and Blacks (rears) and suddenly found my rims stayed much cleaner and I have semi-aero 30mm deep polished Aluminium rims and now they stay nice and shiny.
Ther Salmon's are brill, I can't rate them highly enough, especially in the wet.