Commercial conductive ink is expensive and you’re stuck with the formula available; this DIY version allows you to tweak and customize your conductive ink to meet your needs.
Jordan Bunker wanted some conductive ink for projects but none of the ink he found met his needs–it was either too expensive, the DIY formula was overly complicated, or it was incompatible with the materials he wanted to put it on. After he stumbled upon a white paper by the UIUC Materials Research Laboratory he set out to follow in their footsteps and make his own particle-free, highly-conductive, and low-temperature ink.
It’s not a dirt cheap process, and he gives a fairly stern warning at the beginning of the guide:
NOTE: Please don’t do this at home unless you understand the risks and dangers and know how to avoid them. In fact, it’s best that you have a chemist or someone experienced with how to handle chemicals properly help you.
Ammonium hydroxide is nasty stuff. Formic Acid is even worse (It’s basically liquid pain. It’s the chemical in ant bites and bee stings that makes them hurt). Please respect this stuff.
That said, the results are quite impressive–check out his full build guide for more examples of his circuits-on-glass examples.