Howdy Faylool!
MemphisMyst, below that picture of me is a line, "Blog Entries:" and that hyperlink number 3 just to the right will take you to my blogs. There is one on unicorn tears and butterfly farts. That is what I should have titled it because I cannot remember what I did use for the title... I give an idea of what volume a butterfly fart is, but it is basically what it sounds like, an amount so small that it seems ridiculous.
ETA: Obviously Faylool's 10% is way above a butterfly fart. Might be a good way to go if you're looking for more pucker than sour. And that's the issue with a "set amount" is the amount you needs is wholly dependent on what effect you need, your hardware, and your
sense of taste.