Paper Money

Is ‘starburst’ effect on £5 bank note a trick or a security device?

Does this “starburst” generated by shining a laser pointer through the security window on a Bank of Canada note have a purpose? Several Bank of England notes exhibit a similar effect.

Original images, screenshots from “The Mirror.”

The Mirror, an English tabloid usually known for sensationalism, took a less controversial tack in a July 22 story on a hidden feature on England’s £5 note that is not mentioned by the Bank of England in its online information, yet which has been known for five years.

It published an interview with Steve Mould, a scientist who claims to have found a hidden detail that can only be seen with a laser on Queen Elizabeth II’s neck in the £5 Bank of England note. He had revealed his discovery in a YouTube video he made soon after the note’s introduction that shows him pointing a red laser through the queen’s neck in the transparent window. He said, “If you shine a laser pointer through just the right point on the Queen’s neck, then projected on the opposite wall you’ll see a triangular star field. The question is, is this a deliberate security feature?”

It is unclear, even if deliberate, whether this constitutes a security feature. The scientist thinks not, but rather that it is a side effect of how the queen’s face is printed. “Under a microscope,” he told The Mirror, “you see a triangular grid of ink dots. So what we see projected on the wall is counter-intuitive.

“You might imagine shining a light through that grid of ink dots and those ink dots blocking the light. So surely we would see projected on the wall a grid of dark spots? But we don’t, we see the opposite. We see a grid of light spots.”

It is probably not a security feature. Comments on the video included one that said it also works on the £10 note and another that says “The same thing happens with the little window of my own face, on my Colorado driver’s license.”

A similar phenomenon definitely is a security feature on Canada’s polymer notes, and that is also touted by some as a cool party trick. On those notes, if you shine a laser through the transparent Canadian maple leaf, the value of the note will be projected on the opposite wall.

The explanation for it in a similar video describes the effect as diffraction grating, a splitting of light into several beams in different directions.

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