Spiral: I've had this happen before also after using vinegar to neutralize the
Phosphoric acid that i usually use to etch blades. It seems strange
to me that one acid can be used to neutralize another, but i guess
for some reason it works. Try also heating blades on both sides with
a torch (very carefully). Then apply acid. It seems to emphasize
the high-carbon areas of a blade with some really good results. If
the blade turns out too dark simply repolish, and try again....Dave
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