Yes, subfuscpersona - cream of tarter, or even some vinegar, will help to stabalize beaten eggg whites. However, neither will do what a copper bowl will. Since I hate to recreate the wheel ... try reading what Shirley Corriher has to say about the experiments she conducted at Natalie Dupree's cooking school, and her discussion with Dr. Ing. C. Peng at Perdue University, in her book Cookwise, pages 234-235.
Shaheen's original question wasn't asking about how to stabalize egg whites - the question was "why use copper".
"It ain't what you don't know that gets you in trouble. It's what you know for sure that just ain't so." - Mark Twain