Q & A: Rust and Mold on Waterstones
My set of Norton waterstones
has recently developed
two problems. First, a
brownish stain appears when I
sharpen my chisels and plane
irons. Could this be rust? My second
problem is mold, probably
the result of storing my stones in
damp conditions. Can you recommend
a way to get rid of the
rust and mold?
You’re right about the first
problem. The brown stain
is from the oxidation of small
steel particles. This doesn’t affect
the functioning of the stone and
is only an aesthetic concern.
To prevent mold from growing, put
a few drops of chlorine bleach in the
water that you soak your stones in. To
clean up moldy stones, you can lap
them on a piece of 1/4-in. plate glass
with either 180-grit silicon carbide
sandpaper, or 90-grit carbide particles
(available from auto parts stores).
Despite any remaining stains, the
stones should function as well as ever.
From time to time, your waterstones
will need further lapping. This keeps
the stone flat and clears it of any clogging
This story originally appeared in American Woodworker April 1999, issue #72.