Saturday, June 23, 2012

What Kind of Ink is Used to Make Currency?

Money is everywhere, but how often do you stop to think what it’s made of? The paper is usually either cotton, cotton mixed with other fibers like linen, or plastic. The ink, however, is much more complicated.

Exact banknote ink formulae are kept secret to prevent counterfeiting, but many kinds of inks are used. Usually, banknote ink consists of dry color pigments that are mixed with oil and extenders to create unusually thick ink which will react in a very specific way to the paper used. This helps prevent counterfeiting because the ink will feel different to the touch than regular inks. The inks also differ from country to country. Around 85 different inks are used in the production of British banknotes, and while US banknotes use far fewer colors, the US Bureau of Engraving and Printing, which designs and prints US banknotes, still uses 9.7 tons of ink each day.

Though the exact inks differ, there are still some common inks used in what is known as security printing that make currencies hard to reproduce.

Color-changing inks

One of the most common inks in currency is called optically variable color-changing ink. The ink reflects different parts of the white light spectrum depending on the angle from which it is viewed, which results in the appearance of different colors.

This ink is used regularly on higher denominations of banknotes, including US and euro notes. It is not widely manufactured, which makes it harder to acquire, and it cannot be accurately photocopied, as copiers will only reproduce the ink from one angle.

Magnetic ink

Magnetic ink is mostly used on personal checks. The ink contains a magnetic material like iron oxide, and it is used on the routing and account numbers on the bottom of checks in a system called MICR or magnetic ink character recognition. In MICR, the numbers are passed over an MICR read head, and each character produces a different wavelength that the reader can easily interpret.

Unlike the other inks used in currency, this ink is used more for convenience because computers can read and interpret the characters quickly and the processing of checks becomes faster and more accurate. It does have some security features; however, like color-changing inks, it cannot be easily reproduced using a copier, since copier toner doesn’t usually include magnetic ink.

Fluorescent dye 

Fluorescent dye can show up in regular light, but there are some dyes that only fluoresce, or glow, under special lighting. This dye can mark higher denominations, and it can help stores, banks and other institutions identify counterfeit money. Cashiers or tellers hold the banknote up to a black light, and real money will have pictures, words or numbers that glow under the light but are invisible in normal conditions.

These are just a few of the security measures that governments take to make sure it is as difficult as possible to pass counterfeit money off as the real deal. Many other measures include putting in plastic strips, microprinting and watermarks, and though these measures do help, nothing prevents counterfeiting with as much flair and creativity as the ink used in currency.


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