With huge swathes of people either out of work or working from home, many are now attempting all manner of exciting or silly projects in their downtime. [Emily Velasco] is no exception. She decided to explore the feasability of printing with highlighter ink.

The hack starts with a rather ancient inkjet printer, so old that it works with tractor feed paper. [Emily] set about gutting several highlighter pens and squeezed out the ink reservoirs into a ladle. The printer’s ink cartridge was then filled with the fluid, and a test print was fired off. Upon initial extraction, it appears blank. However, with the aid of a UV light, the printed pattern is revealed. It appears that the inkjet is printing a very faint image, such that the system almost works as an “invisible ink”.
It’s a fun little hack with an old printer, made easier as it lacks the DRM of newer models. It’d probably be quite achievable with a dot-matrix, too. If you’re similarly tinkering in the innards of your peripherals, be sure to let us know. Video after the break.