Cleaning hard deposits

[Pdevito]

I used paint thinner and purple power. Worked fine before. I put sharkhide 2 yrs ago . Do I have to sand it off or use my linear buffer?

 

[jimmbo]

What kind of Hard Deposits are you referring to?

 

[jlh3rd]

It'd help if you were more descriptive of exactly what your trying to do.
and pictures help.