How did Diana Ross' hair get in my eggs?

What the hell is cream-of-tartar? Why do I have to put it in my kid’s homemade play dough?


This is my favorite kind of question because I totally geek out over food science and chemistry. I got kicked out of high school chemistry every day, but once I learned how much chemistry was involved in food, I got interested again. But I digress.
So, cream of tartar, is the solid salt form of tartaric acid. It is naturally occurring and is used in baking and candy making quite a bit.
For your kid’s homemade play dough, first of all, you’re totally super-mom if you’re making your own play dough. So congrats on that. The cream of tartar keeps the salt from crystallizing. Without that, the play dough gets grainy. I think that it makes the play dough taste like play dough too, but I’m not positive: I just guessed that because I checked and “magic play dough flavor” isn’t in the ingredient list.
For meringues, when you are beating egg whites, the egg whites have to “denature” in order to stand up straight and make foam. Here’s a visual for denaturing: Imagine Diana Ross’ hair. Under a microscope, that’s what egg whites look like before they are whipped: lots of tight little curly masses that don’t want to loosen up. When they denature, they loosen up and start to look like Darryl Hannah’s mermaid hair in “Splash,” very loose and wavy. As you keep whipping the egg whites, imagine Darryl’s mermaid hairs all starting to hold hands and stay together. Its cream of tartar’s job to make sure everyone is holding hands really tight and don’t let go. Cream of tartar is like the hair gel in Darryl Hannah’s mermaid hair. When you don’t add cream of tartar to your egg whites, you may notice it start to “weep” or fall. That’s when you get a lot of liquid at the bottom of the bowl and your meringue starts to droop and look really sad. Adding a 1/8 tsp of cream of tartar will prevent it.
In candy making, cream of tartar keeps your sugar crystals from joining together and making a hot mess in your pan. Unlike denaturing, where you want the eggs to hold hands and stay together, in candy making you don’t want sugar crystals to join together. But that’s really hard when sugar crystals are naturally attracted to each other. Seriously, they just can’t stay away from each other… don’t leave them alone for the weekend or you’re asking for it. In this case, cream of tartar “inverts” sugar, or just breaks it down into its basic form so that it can’t run and join the neighboring sugar crystal for a party.