SPY TECH

INVISIBLE INK PRINTER

TAKE A NEW TWIST

ON LEMON JUICE.

M016

BY MIKE GOLEMBEWSKI

JUICY SECRETS: Make your top-secret messages a mystery.

Lemon juice has been used as invisible ink for centuries.

Messages written in lemon juice are invisible to the naked eye. However, when brushed with a mix of iodine and water, they become quite visible.

You can use an updated version of this technique by modifying an

HP ink cartridge so that it prints in lemon juice instead of ink. Here’s how to do it.

TOOLS & MATERIALS

HP inkjet printer
Color ink cartridge
C-clamp
Hacksaw
Chisel
Latex gloves
X-Acto knife
Paper towels
True Lemon crystallized lemon juice ( 15 packets)
Small mixing cups ( 2)
Wide electrical tape
Zip-lock bag
2% iodine tincture

Photograph by Garry McLeod

92 Make: Volume 16