As a chemist in my real life, I TOTALLY CONCUR WITH CHUCK!!!! I am also a member of the safety team. To say you can live and die by the info in the MSDS is not an exageration. The stuff we work with can be nasty. Dyes, especially synthetic ones can be fairly nasty compounds, mix them in a solution containing water, or alcohol, and they can be more readily absorbed into your system. Veg tanning uses tannins, same compounds can be found in walnut hulls, what make unwashed acorns inedible (quite tasty if prepared correctly). I was told (no documentation, but the teller lived on a reservation in Canada) that the natives would toss walnut hulls into deep holes in creeks, the fish would die, float to the top for easy harvesting, wouldn't mess with the flavour and the running creek would clean out the toxins in due course. Don't get me started on the toxins involving the chrome tanning process, so if you buy one of those home tanning kits, please read the MSDS and follow the directions.