Paper Money

Supercritical carbon dioxide cleans grungy paper money

Paper money like these $1 Federal Reserve notes are worn enough and too dirty to be accepted by most vending machines today. But a new cleaning method might extend their usability.

Coin World image.

Don’t try this at home, but scientists have come up with a way to wash those worn and grimy dollar bills you might have in your pocket.

Using something called supercritical carbon dioxide could help central banks extend the life of their paper notes.

According to a Jan. 8, 2014, post on Popular Science magazine’s website, “scientists successfully removed the human gunk and motor oil from dollar bills by using supercritical carbon dioxide, a fluid commonly used in other cleaning processes that acts like both a gas and a liquid. The bills’ security features such as holograms and phosphorescent inks stayed intact, safely and effectively preserving the banknotes.”

The article notes that “this cleaning method could prevent bills from becoming the ratty, old ones that vending machines hate and that eventually need to be disposed of.”

And here’s the part of the story that possibly comes under the TMI (too much information) heading.

“The primary source of a banknote’s aging and eventual yellowing is human sebum, the oily waxy substance the body produces. Over time it builds up on the surface of dollar bills where it reacts with oxygen in the air and turns an aged yellow,” according to the article.

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