12.2.2010 12:51 PM

What Is Money Made Of?

Is recycling money possible? Can we improve the environmental impacts of the U.S. Mint and Treasury?

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Photo: Amanda Rohde / Istock

By Kate Forgach

Money doesn't grow on trees, literally. The material on which bills are printed is actually a custom blend of 75% cotton and 25% linen, created by Crane Paper Company exclusively for the U.S. Treasury. This special mixture is known as "rag." It's much more resilient than paper and can't legally be used by anyone outside the U.S. Bureau of Engraving and Printing.

Unearthing the metals used for our cash coins is another matter, however. Pennies are made from copper-plated zinc, while nickels, dimes, quarters and half dollars are composed of cupro-nickel, a copper-nickel alloy with minor strengthening elements such as iron and manganese. The $1 coins are made of manganese brass.

Experts believe there may be insufficient reserves to sustain current high rates of copper consumption. Some countries, such as Chile and the United States, still have sizeable reserves of the metal, although they are extracted through large open pit mines. The production for zinc ores, however, produces large amounts of sulfur dioxide and cadmium vapor. Smelter slag and other residues of the zinc-mining process also contain significant amounts of heavy metals.

As to nickel, mining may require blasting, crushing and grinding of rock, 99% of which becomes waste rock and tailings. Some say the next generation of environmentally friendly mining may extract very low-grade ores through heat, pressure and chemicals, without these problems.

On the other hand, like the linen-cotton blend used for dollar bills, the government selected these metal mixtures for maximum durability. The U.S. Mint estimates the average life span of a coin at 25 to 30 years. Compare that to 18 months for a $1 bill and nine years for the less-handled $100 bill. In addition, all coins deemed no longer fit for circulation are melted and reused by the U.S. Mint. This isn't possible when "paper" money is mutilated or degraded.

The U.S. Bureau of Engraving and Printing churns out about 38 million currency bills of varying denominations daily, worth in total about $750 million. Printing plants located in Fort Worth, Texas and Washington D.C. use 18 tons of ink per day just to keep up.

An offset printing process is used for the first stage of paper currency. The imagery is first transferred onto offset printing plates by photoengravers and the image is "burned" onto a thin sheet, or plate, of light-sensitive steel.

The next step of the process is known as intaglio printing, pronounced in-tal-ee-oh. In this process, ink is applied to a plate so it remains only in the engraved areas. Paper is then laid atop the plate and the two are pressed together under great pressure. As a result, the ink from the recessed areas is pulled onto paper, creating a raised-ink image. Intaglio printing is used for the portraits, vignettes, scrollwork, numerals and lettering that are unique to each denomination.

Security features used on the various denominations and added throughout the printing process include a portrait watermark that's visible when held up to a light, two numeric watermarks on the $5s, an enhanced security thread that glows under an ultraviolet light, improved color-shifting ink that changes color when the note is tilted and, on the newly redesigned $100 notes, a 3-D security ribbon.

The sheets are photographed multiple times throughout the printing process and a perfect "golden image" is created at the end. Within three-tenths of a second, the computer decides if the sheet is acceptable, rejecting any bills with such defects as ink spots, ink deficiencies or smears.

Now let's move on to the stuff that jingles in your pocket: Coinage.

Each year, the U.S. Mint produces between 14 and 28 billion circulating coins. Roughly 65 to 80 million coins are minted every day and fast-paced presses churn out 750 new coins every minute.

The process begins when computer-generated dies impress blank metal discs using high-tonnage force. Any remaining metal webbing is recycled to make new coins.

Blank discs are sized appropriate to their coins and heated to over 700 degrees centigrade to soften the metal. To make the blanks bright and shiny, the metal is then cleaned and the edges are finished before the design is stamped onto the face of the coin.

To create the image, one die (known as the anvil) is held motionless and the other die (known as the hammer) strikes the surface. Golden Dollar coins require the greatest force, and pennies require the least force.

Once completed, the coins are inspected and any defects are scrapped and sent to coin destruction machines. These machines use two high-pressure rollers to mutilate the metal before passing it on for recycling.

Author Kate Forgach writes for several money-related blogs, including topics like saving money with coupons and living frugally.

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