Probably not the blood. I cleaned up the cut before continuing onward. Also, there was no drops of blood in the lather.
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Here Guys,Carbon Blade,cleaned with acetone.Wet alum block,wipe finger on blade,15 mins,done.
http://i22.photobucket.com/albums/b3...ne/puma001.jpg
I myself have experienced the tarnishing that can happen on a carbon steel blade from alum but even more so the remnants of a styptic pencil. I have taken to using a small little wet rag or piece of chamois to aid my grip. If I do happen to use a styptic pencil I shave around the area very carefully and ensure to rinse off thoroughly before the next pass.