Tools of the Trade

For this Tools of the Trade I have another... tool, for lack of a better term, that I use when I watercolor. Ox Gall. Yes it really is ox gall. I've been told that it tastes terrible (sometimes people stick their brushes in their mouth for various reasons, it's a bad habit it sounds like using ox gall and accidentally sticking your brush in your mouth could forever cure you of that.) I don't know about the taste but I do know that when I dropped the bottle and a bunch spilled out, it didn't smell really good (while it's been contained in the bottle I've never really noticed a smell.).
Anyway ox gall was recommended to me to solve a problem I was having. The problem was the pigment... not being well absorbed into the paper(?) if that makes any sense, anyway the remedy was to add ox gall to the water I use. Usually before I start painting I'll add a drop or two ox gall to the well before I mix up the paint. It's been working well for me and the bottle's lasted a long time (except for dropping and spilling).