See-through letters

December 12, 2000

Why seal envelopes if the police can see inside anyway?

A SPRAY that makes unopened envelopes transparent-so the letters inside are as easy to read as postcards-has been developed by a company in the US. And the spray leaves no trace, says its inventor, Mistral Security of Bethesda, Maryland.

"With a business card in a brown envelope," says company spokesman Bob Schlagel, "you can read the card, the e-mail address, the telephone number, everything." Schlagel says that the spray, called "See-Through" was developed to let police forces inspect potentially dangerous packages, like a letter bomb.

Described as a "non-conductive, non-toxic, environmentally safe liquid", the spray has been tested to make sure it leaves no trace on envelopes, Schlagel says. "It leaves an odour for 10 to 15 minutes," he adds, "but apart from that, there's no smudging of ink on the envelope or on the letter, no watermark, no evidence at all."

He says tests have shown that the spray works on all colours of envelopes, unless they have a plastic barrier like those found on padded envelopes. Mistral's distributors will only sell the product to "law enforcement agencies", he adds.

John Wadham, director of Liberty, the human rights organisation, says that police in Britain would need a warrant to use such a spray to examine letters. But Simon Davies, director of Privacy International, a London-based human rights group focusing on surveillance issues, says the spray could tempt security forces to bend laws. "It's an opportunity for governments to side-step legislation on mail interception and opening," he says. "It's an ethically questionable product."
Author: Ian Sample

New Scientist issue: 16 December 2000


New Scientist

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