My brand new JemJR has weird white dust inside wood. I already tried to clean it using some paper and water. It looked perfect right after cleaning it, but it returned once the fretboard was dry.
What is it? How could I remove it?
This was answered on the Woodworking stack: getting slurry out of wood grains
It's liquified sanding dust. Fine-grit paper creates tiny particles which mixed with the finish and dried into the grain.