Hi Millie, here's a little science lesson about cream of TarTar from Wordpress
"Cream of tartar is most often used in baking as either a stabilizer or a leavening agent.
This gave me a total flashback to 7th grade science class.
Remember learning about acids and bases back in the 7th grade? Well, egg whites have a pH of about 9, which makes them a base. Cream of tartar is about a 3 so just a little bit edges the egg whites towards the acid side of things. The acidity helps the coiled strands of protein (egg whites) relax and unwind. Think of it as unraveling a sweater! The long strands stay whipped up.
You could use other acids to achieve the same result, but most edible acids (like vinegar or lemon juice) have strong flavors. Nobody wants their meringue to taste like vinegar. Cream of tartar doesn’t taste like anything. It’s more expensive than vinegar, but one jar of the stuff can make about a hundred meringues recipes."
