Mathematical model uses the way dye moves over time within skin to predict how a tattoo will blur and fade It may be small comfort if you wake up after a heavy night with a hazy memory and some unsuitable words tattooed across your shoulder, but it is now possible to predict what a piece of body artwork will look like in years or decades hence. A mathematical model uses the way dye moves over time within skin to predict how a tattoo will blur and fade. The tool may also be some comfort to the handful of celebrities sporting misspelled tattoos in foreign languages. The footballer John Carew can look forward to the day that his “my life, my menstruation” tattoo , which was supposed to read “my life, my rules” in French, will be illegible. Britney Spears, who sports a Chinese tattoo that was supposed to say “mysterious”, but instead reads “strange”, may be keen to find out when hers will fade. Tattoos are created by puncturing the skin with a steel needle up to 3,000 times a minute and depositing a drop of insoluble ink into the dermis with each puncture. The indelible markings are not resistant to the effects of ageing, however, and over time the ink particles disperse as the cells that contain them either divide or die and exit the body. How quickly an image will degrade depends on factors including the tattoo size, detail, location and exposure to the sun. Skin type, age and dye ink will also influence how a tattoo disperses. Ian Eames, a reader in fluid mechanics at University College London, who has published details of the model in Mathematics Today and , said small details in a tattoo were lost first while thicker lines were less affected, and larger tattoos fared better in appearance than smaller ones. The details of complex patterns are lost after about 10 years. Eames’s model enables him to estimate the movement of ink particles and predict how a particular design will change with time. “The dye spreads in some sense like heat spreading along a metal bar. But the rate of spreading is very, very small and takes many years to spread a few millimetres,” he said. This may come as a surprise to the growing number of human canvasses in the UK. Tattoos have become more socially acceptable, with the likes of Samantha Cameron sporting a dolphin on her ankle, and a fifth of all British adults now have tattoos. Beauty Fashion Mathematics Emine Sinmaz guardian.co.uk