Black streaks during hand planing

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27 Nov 2020
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I have started to plane white oak and I have noticed black streaks on the wood. It looks like some metal contamination from my beloved no.5 hand plane. Also, the area behind the mouth continually turned black. I cleaned it with sandpaper but, it started turning black again. I have vacuumed the plane and also made sure that I do not cary leftover particles from the sharpening to the plane.

What might be the cause of this issue?

Thank you.


could be mineral streaks in the wood itself? or something to do with the tannin inside the wood.
The wood probably isn't as dry as you think it is. This is a problem when working with green oak as all the steel tools turn black because of the tannin- this can then rub off on the wood.
Tannin in the wood, iron and water are the cause. Common with tannin rich woods, metal planes, and sweat or other sources of water. It's not a problem to worry about. Final polish prepping of the wood removes any black marks. Black marks on the soles of planes can be ignored. Slainte.
Thank you very much all, you are right. This is air-dried oak (I am about to use it as my workbench top) and yesterday I trimmed 150 mm off. It has a moisture content of up to 15% near the center. I am again a bit wiser :)

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