Originally Posted by YooperBrew
What does the cream of tartar do?
The author, Stephen Buhner, says it's used for head retention, which I can sort of believe since it's used as a stabilizer for meringues sometimes. I think it is probably also used to add a bit of acidity to what might otherwise be a "flat" tasting drink. It was in almost every ginger beer recipe in the book, so I decided to include it, although I felt that it might be redundant to the lemon, as far as the acid contribution was concerned.