[ynotbrusum]

I am not sure of the speed of the distilled vinegar process - I soaked in a 5% solution (straight from the gallon jug of the stuff, which is labeled as 5%) for about an hour and upon scrubbing with a blue scrubby, I found no discernible difference occurring, so I dumped it and rinsed repeatedly and am now soaking my BK in PBW for the second day.  I am pretty sure it will peel off the beerstone, but I have BKF at the ready, if the PBW falls short...

[HoosierBrew]

I am not sure of the speed of the distilled vinegar process - I soaked in a 5% solution (straight from the gallon jug of the stuff, which is labeled as 5%) for about an hour and upon scrubbing with a blue scrubby, I found no discernible difference occurring, so I dumped it and rinsed repeatedly and am now soaking my BK in PBW for the second day.

Thanks for the info. I was gonna use it soon but that doesn't sound like something to spend time on.

[MoreHops]

I used to have this problem when I would just soak my brew kettle with PBW after brew day.  It would leave a lot of residue.  I started using about 1 Oz of 85% phosphoric acid in about a half gallon to gallon of water and letting that soak followed by PBW.  That usually worked pretty well but not perfect.  Now I just scrub with Bar Keepers Friend after I'm done brewing.  That stuff is like magic. No need for PBW or the acid wash. 

[dbeechum]

Acid 5 is my preferred cleaner of choice, but 5 star is a little wary of that one being in the homebrew market since you can very easily be an idiot with it.

Otherwise, I use citric acid or BKF.