O.K. I am quite enthused about trying out tannin for toning after reading this thread. However, I am a little confused.
Jason talk about using Tannin from a winemaking store and other are talking about using tannic acid. From a general search I did, it seems that these are not the same thing. I can get tannic acid from my chemistry supply place but it seems somewhat expensive.
Tannic acid is a liquid form of tannin usually derived from hardwoods.
There are lots of "kinds" of tannins.
The tannin I use comes as a powder, and is supposedly derived from grape seeds and stems. It's pretty cheap.