Q &A

Q What exactly does bleach do? If I soak a cracked dish, the stains seem to be gone - but are they really?

A The active ingredient of bleach is sodium hypochlorite, which is made up of three common elements - sodium, oxygen and chlorine, said Oregon State University professor of chemistry May Nyman. The rest of what is in the bleach bottle is mostly water.

"Of those three common elements, the chlorine is really hungry for electrons," Prof Nyman said. "It doesn't have enough. The food that gets stuck to your dishware is basically hydrocarbons, and they are great sources of electrons."

What follows is a chemical reaction.

"The chlorine grabs the electrons from the hydrocarbons, the oxygens and chlorides get bonded to the carbons, and this makes your food stains water soluble, but just enough to unstick them from the dishware," said Prof Nyman.

As a result, the stains come unglued and can simply be washed down the drain.

Food particles get stuck in cracks, making them more visible. When the food is released by the bleach, the cracks are not so visible any more, though they are still there.

But the stains themselves "are really gone", Prof Nyman said. "This reaction is what scientists call favourable, meaning it won't go backwards."

NYTIMES