Great story in this month's Wired magazine about the Inkjet Counterfeiter.
"Counterfeiting is considered such a threat to the fabric of the United States that, along with treason, it is one of only two criminal offences named in the Constitution. Although now better known for its role in presidential security, the Secret Service was actually founded by the Treasury in 1865 to combat currency counterfeiting.
"Fake bills make up a tiny fraction of the cash in circulation at any time – the Service puts it at less than 0.1 per cent – but this still amounts to some $780 million in the US alone. And its impact can be significant: losses incurred by accepting counterfeit currency are not covered by insurance, and a run of fake bills will shake international confidence in the dollar. In the UK, where known fake notes made up approximately 0.03% of all sterling in circulation, £13.7 million worth of counterfeit notes were removed from circulation last year. The vast majority (98 per cent) were £20 notes.
"Almost every physical attribute of the money in your wallet was conceived with the intention of making it hard to duplicate. UK notes are printed on paper made from a mixture of cotton fibre and linen rag; euro notes are printed on 100 per cent cotton; and US notes are printed on paper composed of 75 per cent cotton and 25 per cent linen, giving it a feel that's easily distinguished from the smooth wood-pulp paper commonly used in copiers.
"In 1996, US currency underwent a significant redesign, specifically to combat the growing use of colour copiers and computer scanners by counterfeiters as the technology became more sophisticated and widespread. The US Treasury has since introduced three further series of notes, each employing more complex security features: the most recent of which includes coloured backgrounds, intricate patterns of microprinting, water-marks, embedded security threads visible when the bill is held to the light and ink that appears to change colour, depending on the viewing angle.
"Security features of UK notes are similar and include raised print (eg on the words 'Bank of England'); watermarks; embedded metallic thread; holograms; and fluorescent ink visible only under UV lamps. There are three printing processes involved (offset litho, intaglio and letterpress) using a total of 85 specialised inks. Euro notes incorporate many of these features too, including watermarks, raised print, a metallic security strip, holograms, and colour-changing ink. But even the latest technology cannot thwart every forger. 'The security features make it more difficult', says Special Agent Edwin Donovan, 'but there's no such thing as "uncounterfeitable".'"
The best bit however, was where the counterfeiter found a problem with the paper he was trying to print onto. Most of the paper, when you applied the marker pen to test if the notes were real or fake, found that the colour turned black (fake) instead of staying yellow (real).
"There was a problem, Talton says: 'It wouldn't take the mark'.
"Counterfeit-detection pens mark yellow on genuine currency but brown or black on fake. Talton didn't know why. At first he thought the Treasury treated the paper, so he experimented with chemicals he found at the garage and even tried dipping his notes in fabric softener. Nothing worked. Frustrated, he began to take a detection pen everywhere he went, trying it on any paper he came across. He was about to give up when one day, in the toilet, he found himself staring at the roll of tissue. He took out the pen: the mark showed up yellow. Talton discovered that toilet paper, Bibles, dictionaries and newsprint are all made from the same recycled paper pulp, and all take the yellow mark."
Oh yes, and if you're really into counterfeit schemes, Mint's Blog has a list of the nine greatest schemes of all time.