I saw someone at a festival using what I thought was black henna.  Her hands were all black and the stain left on the everyone's skin was black.  When I asked her why, if her sign said natural henna, her hands were  black.  She said it was black henna (this is in Canada).  I said "you're using PPD?"  She said it was PPD free.  So I asked what was in the paste and she responded that it was arrowroot powder.  Now I think I've heard something about this at some point here, but I'm not sure.  Is it possible that she wasn't using PPD, yet the stain was black, and what exactly is arrowroot powder?