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Way of seeing sanding scratches on raw fir

1K views 10 replies 9 participants last post by  HowardAcheson 
#1 ·
I have sanded a reclaimed fir table top through a progression of grit #'s. Is there a substance I could apply to it that would bring out any sanding scratches without affecting the wood surface prior to staining? I don't want to wet it with water as that would fuzz up the grain and I hopefully am done with sanding.
Thanks
 
#2 ·
A low angle light source would work well. Hold a light source near perpendicular to the face of the board, and any rough spots usually stand out. My personal favorite method is to scribble all over the board with a pencil whenever changing grits. Then, once you sand, when all the pencil is gone you know you've sanded everywhere
 
#4 ·
Actually wetting the wood between grit changes when sanding is a great way to get rid of any scratches that may be on the wood. Since you are beyond that point already wiping the wood with a solvent like mineral spirits or naphtha would give you an idea of what the wood would look like with a finish on it. Also what epicfail said about putting a light at low level is a good way to see if there is any defects on the surface. You could also look it over good after staining however if there is a problem the stain makes it very difficult to fix. If it needs more sanding the stain gums up the sandpaper and then when you re-stain the wood won't accept the stain again. You would have to use a darker color to achieve the same look.
 
#8 ·
I use a hand held spotlight to inspect before staining, early morning sunlight coming through an open door or window works well also but only in the morning and evening when the angle is low. It is also important to check with the grain and across the grain as scratches only show up when shadows are created.

Water based dye also works well before the final sanding grit. I will add a tiny bit of dye powder to the water to wet the wood which will bring out any scratches and add a guide coat to make sure I sand the entire panel. Water based dyes also don't gum up the sandpaper but powder off nicely.
 
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