Homemade aluminium foil capacitor

Thread Starter

Babu Mistry

Joined May 25, 2019
Hi there,

I'm interested by capacitors and super capacitors and so i decided to make my own.
This is the textbook, school science project variety of capacitor, with A5 sheets of aluminium foil
separated by photocopy paper (as the dielectric).

This has been interesting. I've been able to get my capacitor to slowly release it's
charge over a period of 70 seconds (after the battery is disconnected)
before the display on my multi-meter registers zero volts.

Commercially manufactured capacitors can hold a charge practically indefinitely.
What i would like to know is:
Why does my homemade capacitor not hold a charge:
(It starts to discharge the very moment i disconnect the battery).

Both (aluminium) sheets are surrounded on both sides by paper.
It's not clear to me how, or why, my capacitor is discharging.

Thank you to anyone who can offer some suggestions or solutions

Sally :)
Hi Sally it might have a short in between the paper and aluminum foil. now I need your help how long is foil used in capacitor 12 Volt 0.22uf any idea.

Mod edit: Moved from old thread.


Joined Jan 12, 2015
I made a variable capacitor once with my daughter who was about eight at the time. I told her we were going to make a radio that didn't need batteries and make it out of ordinary junk (except of course for a diode!).

I calculated the approx. capacitance I could get and the approx. inductance and found I could get some medium wave frequency without too much effort.

The variability was essential though in order to adjust and find any stations.

The way I did that was a tall empty aluminum beer can, some very thin paper wrapped around that and a kitchen foil sleeve around that. The sleeve fit snug and could be slid back and forth.

Attaching wires to this was a drag but doable with fine wires and tape.

Well it worked (a crystal set) and she was amazed, it was great to see a young child mesmerized by something like that using pretty much kitchen junk.

Thread Starter

Babu Mistry

Joined May 25, 2019
Hi, Frind's,
Thanks for all the answers, but I just managed my problem instead of making a paper capacitor.
I bought a car distributor condenser open its outer Mattel casing and used the inner foil capacitor in my project it works very fine.
Thanks, Friends.