Washing-up liquid

Washing-up liquid was soap used in the washing up. It was sold in supermarkets. (PROSE: There's Something About Mary)

The Sixth Doctor once scrubbed at grease and mutton fat on a battered aluminium roasting tin with washing-up liquid. He also dropped fistfuls of cutlery into the greying water in the sink. The roasting tin was eventually scratched but shining, while the cutlery was draining. (PROSE: The Earwig Archipelago)

In 1982, the First Doctor hung out of a helicopter with a large container of washing-up liquid, in pursuit of a giant mosquito, and made the creature explode when he sprayed the stuff at it with a hose. Bubbles burned on its skin before it exploded in a mess of wet and yellow gunk. (PROSE: Do You Smell Carrots?)

While doing the washing up with Isaac, the Sixth Doctor commented that Isaac knew what it was like when the life of a nation was shaped around the whims of a man who could not even ensure them access to good washing-up liquid. (PROSE: The Earwig Archipelago)