There was an issue of Popular Electronics back in the day that had a reprint of a “what hams did in the 20s and 30s or parts” that described rolling your own caps.
They also made their own resistors out out graphite, but more useful were test-tubes full of water with leads submerged in them. Which also made an interesting variable resistor that might reach the boiling point during heavy use.
Open measuring flask full of salt water with one fixed electrode. Depth of the other electrode in the solution varies the resistance. Amount of salt varies the conductivity.
One of the Boy’s Book of Experimentation projects that would have most politically correct, everything must be safe people running in terror involved a board, two carbon rods from the old Eveready/Rayovac 6 and 9 volt batteries. One set had 1/4" carbon rods, the other 1/2", some sort of glass flask to hold the salt solution and instructions to build a framework to hold another set of the carbon rods. You were building a carbon arc lamp with instructions to start with the electrolyte rheostat having its rods no more than a half inch into the salt solution when you first tried to draw an arc. They also showed you how to make an electric furnace using an iteration of the carbon arc under an inverted flower pot.
Funny that none of my friends and I died of this stuff. We knew it was dangerous, but most of us build careers on what we learned.
This would’ve been much better delivered as text. There was about 30 seconds of informational content, and 7:36 of filling time. I’m also very disappointed by the lack of discussion of any theory at all.