How to remove white marks from PLA When you cut or break a PLA model (for example to remove support) it often leaves an ugly while mark where the removed piece was connected.

Sanding also tend to leave dull white scratches on the sanded surface.

What can I do to restore the white areas to the original filament color?
A quick blast from a heat gun will very slightly reflow the surface texture and eliminate white marks. 

However, it's important to avoid over-heating the perimeter layers or you'll see them soften and sag into the infill. So wait for the heat gun to get fully hot and then use a short duration of high heat. Let the part cool between attempts if you don't get it all the first time, or need to clean up a large area. 

Incidentally, the heat gun will also help clean up strings from travel moves.