Re: The proper "Why wet sand?" thread
Well...several things..
First grit to grit wet/dry paper is Courser than dry paper.
Wet sanding removes residue while sanding therefore it cuts faster and lasts longer.
Wet Keeps down dust ( good for sanding inside boats ).
During the finer grit sanding wet sanding is preferable as to not create scratches from buildup of dust.
Hand wet sanding is also Great for putting little holes in your finger tips that hurt like hell

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Its also good for removing finger prints just in case your spouse has a print kit and you were the last one in the cookie jar

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YD.