Fine sanding discoloration in light colored wood

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Jay Sweeney

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Joined
Mar 21, 2016
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14
Location
Sitka, Alaska
Has anyone else experienced discoloration in light-colored woods (maple, yellow cedar, etc.) when sanding with ultra-fine sandpaper? I seem to continuously get grey or black discoloration when sanding with finer than 400 grit sandpaper. I often have to go back to 220 grit and re-sand to get rid of it. What causes it? I use water-based sanding sealer and wood pore filler. Anyone found a way to avoid this discoloration?
 
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Skie_M

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Aug 7, 2015
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Lawton, Ok
What speed are you spinning at when getting this issue?

I often find that it's from sanding too fast ... the glue used to make sandpaper is one that is temperature based, if the paper heats up too much, the glue will re-melt, causing the sanding particles to transfer to your work, which is a hell of a pain.

You'll sand best at 750 RPM, according to 3M's studies ... best speed combined with the heat dissipation properties of the materials.
 

jttheclockman

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Joined
Feb 22, 2005
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12,756
Location
NJ, USA.
I am going to assume a few things because you did not supply enough info. If the sanding you are referring to is on a pen, are you using the metal bushings??? If so you probably are picking up metal dust and transferring it to the blank and you ere embedding it into the sandpaper thus will continue to do so. I suggest get rid of the metal bushing and make some delrin bushings and sand between centers.

Of course my favorite theme when it comes to sanding pen blanks is don't do it. Learn to use your skew and go from turning to finishing without the hassles of sanding.

Now back to sanding. It could also be you are seeing burn marks. The speed at which you sand is crucial 800-1000 is all that is needed. When you get to the higher grits the pores of the wood are being closed down and the sanding dust is building under your sandpaper and becoming heated. The fine grain on top of the wood can become singed and this looks darker than the rest of the blank. Use good quality sandpaper and sandpaper should not melt where the particles fall off and glue exposed. That is some poor paper if that is happening.

That about sums it up. Good luck.
 

Jay Sweeney

Member
Joined
Mar 21, 2016
Messages
14
Location
Sitka, Alaska
Thanks for the advice

Thanks for the hints and the advice! I have definitely been sanding at a higher speed than everyone recommends.:)
 
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