[William Finucane] is making his own litmus paper by harnessing
the power of cabbage. The process is much easier than the faux
gunpowder he made, as it take just the one ingredient and a few
kitchen tools. In case you’ve forgotten your High School
chemistry, Litmus is a set of dyes that change color when
exposed to basic or acidic materials. It is common in liquid
form, or as a paper. [William] is getting his dye from the
leaves of red cabbage by running half a head through a blender
with just a bit of water. Once that is reduced to pulp and
boiled in the microwave (mmm, must smell great!) he separates
the liquid using a coffee filter. A fresh coffee filter serves
as a donor for the substrate, just dip some strips in the
cabbage juice and let them dry. You can test them with some
Ammonia as seen in the video after the break, or just start
grabbing whatever is under the sink and see what happens.