Troubleshooting Light Color in Walnut Grain

Sanding can pack fine dust into wood grain; wire brushing after sanding might get that out. September 18, 2012

Question
I have been using walnut on several projects and have noticed that after applying the finish the grain contains some light streaks. Sometimes it is quite a lot and in other instances it is just small pockets. Prior to sanding I remove as much dust as possible with a vacuum and compressed air. The finishes I use are freshly mixed shellac and Rustin’s plastic coating.

Forum Responses
(Finishing Forum)
From contributor Y:
Since you also state that there are "some" areas it is most likely that you will have to wire brush with a soft brass brush to insure that "all" the material in the pores is really removed. If sanding with finer grits 220-320, etc., the wood dust can easily get compacted and is not always easily removed by vacuum or other methods. Always go with the grain when brushing is required.

Since it also sounds like your just doing natural finishes with no color being applied, or at least not any you've stated, I will assume that it is possible to just wire brush those areas in need and not the entire surface, though you may want to lightly re-sand those areas gently again so as not to fill the pores once more.

The less pressure and heat in sanding the less compacted the wood dust will be! What will also help is blowing the dust out more frequently, rather than waiting for longer periods of time or maybe even not at all as your case may be, with more frequent blowing of the pores, less build up or compaction will occur. At the very least it should be done when switching from one grit to the next lowest.

Another help would be to wet the surfaces with alcohol or if more time is needed to view, VMP Naptha or Mineral spirits, so that you can inspect the surfaces to make sure you have not missed anywhere before applying your shellac or other first coat clears you may use. Experiment with the suggestions. I think you will be happy with the final results, if not, others may have more input as to what else may be done.


From the original questioner:
I tried that out and it worked great. I can see now that just using the vacuum is not enough to remove lodged-in dust.

From contributor H:
Unless you have very deep pockets of grain or dust accumulating in the corners of doors, your finish should wet light dust and render it invisible. Part of our standard sanding procedure is to wet the wood down with water between 120 and 150 grit. This will remove dust in the grain as well as swell the wood fibers for a better final cut. Could your issue be mineral concentration in the grain?

When using California walnut we have noticed whitish streaks in the grain pockets that are not removable and have an iridescent look. They have a definite color shift when finished (appear and disappear depending upon the angle that you see them at). Wire brushes and wood tend to scare me, unless that is the look that you are after.

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