Q: How can I make conductive paint into a liquid switch that turns a lightbulb on and off? --Patrick Stevenson-Keating
A: You’ll need to suspend the water-soluble conductive paint in a liquid it can’t mix with: an oil with low viscosity. We recommend clear baby oil. Put the paint and oil in a hollow glass base below the lightbulb. You can turn on the lamp by tilting the base until the blob of electric paint makes contact with two electrodes extending from the bulb. To turn off the light, simply rotate or tilt the lamp until the paint is no longer bridging the gap between the electrodes.
--Peter Krige, Bare Conductive
As told to Alissa Zhu
This article was originally published in the April 2015 issue of Popular Science, under the title "Tech Support."