In a Chinese farmers market, stooges handed over either clean or dirty notes, then asked for 500g of an extra vegetable.

FORBES: Dirty Cash, Dirty Minds: The Psychological Consequences Of Filthy Lucre

So does black market, or the supposedly clearly distinct clean and dirty money.

NPR: Tracking the World's Black Market: 'Illicit'

Or can a down and dirty approach sometimes help you clean up?

BBC: The bottom line on being messy

Under the center consoles you can tell if the carpet appears genuinely clean because it is or if it was cleaned from being dirty.

FORBES: Following Hurricane Sandy, Here's How To Avoid Buying A Flood Damaged Car; Don't Get Soaked

You can also shake the device to clean the text in case it ends up getting "dirty, " or misaligned.

ENGADGET: E Ink reference phone and flexible display hands-ons (video)

More fascinating, less dirty - Dyson now engineers motors in a room so clean no pollutants, pollen or dirt can damage the finely tuned technology being made by the highly calibrated production line.

BBC: Technology