Picture of Creating your own ferrofluid without caustic chemicals

This instructable explains how to make your own ferrofluid without using any chemicals.
The magnetic particles will be extracted from an audio cassette and they'll get mixed with vegetable oil (regular cooking oil).

This instructable is relatively short because there isn't much more to explain about it. It's really easy to do, but it takes a few hours to do.

Please pay attention to all notes regarding safety!

Step 1: Requirements

These are the parts you need. I'm sure you have all of them at home already.

- an audio cassette.
- a sharp knife.
- vegetable cooking oil.
- a small bucket for the ferrofluid.
- a metal plate (see step 3).
- a strong magnet (not required for actually Making the ferrofluid).
- some stick to mix the particles with the oil.
- scissors.
- a lighter or matches.
- a fire extinguisher for if you set your house on fire with the lighter.
- a piece of cardboard with small ridges. (or no ridges at all is even better)
Romninja10 months ago

While I know this ibles is ages old,i'm still going to ask my question, what happens when you put your ferrofluid in water? Does it float around?Sink?Does the magnetic powder mix with the water? I'll make this when I've got the time for it.

-max-3 years ago
stick the magnet inside it!
Electorials (author)  -max-3 years ago
But then I'll never get it clean again :(

exactly.. hehehe

nbeched2 years ago
I had to repeat these steps 14148 times :)
Electorials (author)  nbeched2 years ago
haha xD me too
strmrnnr3 years ago
One of my Subscriptions on YouTube put this video out about mineral oil. The man is a chemist. You may even find some experiments with the liquid in his past videos.

This one concerns mineral oil. Did you know baby oil is the most refined mineral oil on the market and it is cheap.


NurdRage is his Handle.

Happy New Year Brother.
strmrnnr3 years ago
This Instructable may give you the metal you are looking for. It does get away from the tape theory, but will possible give you another source for material.

I had built one of these (easy as pie or easier), but never had a chance to use it due to my gypsy nature.

BrittLiv3 years ago
Are you sure, that this is pure ferrofluid? I don't think so, because only type I cassettes are based on gamma ferric oxide. In your case it says big "Chrome" on the cassette, so I'm pretty sure it's based on a mixture of chromium dioxide and a bit of ferric oxide. Maybe that's what's "wrong" with it...
Chromium oxide is ferromagnetic as well, but I would still try to use a cassette, that is based on pure ferric oxide.
Electorials (author)  BrittLiv3 years ago
Thank you for telling me about that.
I also think that that's the problem, I'll try using with other cassettes.

But how can I make sure which cassettes have pure ferric oxide tapes?
I'm not sure, as far as I remember, it says so on the cassette (maybe not on every type). The possibilities are:

Fe2O3 (gamma ferric oxide) (those are apparently the older ones)
Fe3O4 (magnetite)
or CrO2 (chromium dioxide)

Maybe the colour of the tape can be an indicator, but I'm not sure about that... Ferric oxide is red-brown, Chromium dioxide and magnetite are black.
Electorials (author)  BrittLiv3 years ago
Oh! Thank you Very much!

I indeed also have red-brown tapes (most of them are) but I can't seem to separate the magnetic band from it :/
try submerging it in acetone it will melt the glue and separate the ferric oxide from the plastic film
this might be silly but what about using a VHS tape?
strmrnnr3 years ago
Maybe it would by more active with a thinner oil - grapeseed maybe. I like the idea. Have you tried video cassettes? Wondering if the powder is a better grade metal.
Electorials (author)  strmrnnr3 years ago
I'll try both ;)
but I don't know what's wrong with this ferrofluid :/ it doesn't make those cool spikes.
Mmmm... I think that it could be for two reasons, or maybe the relation between them: The fluid's viscosity and the magnet's size/strength. What do you think?
I'm not an expert or anything but I thought you had to have something acting as the surfactant that kind off pushes it all away from each other. I would think you would have to use something else. (never tried it, just suggestion/curiosity)
Electorials (author)  FueledbyRamen3 years ago
I could try that too yes
Tolderian3 years ago
I'm sure there's a reason... but I'm dumb... so I'm gonna ask. Since there aren't stupid questions... just stupid people. I.e., me.

Why not use mineral oil? Wouldn't veggie oil go bad and smell like super-anus in time?
Electorials (author)  Tolderian3 years ago
It does already smell super-anus :P

It's not a stupid question at all because I also don't know the answer. i'm going to try with different types of oil to see which work best.
Try mineral oil. You can actually submerge your computer in it as it does not conduct electricity or go bad.

I watched a vid awhile back on using it on a computer aquarium. I thought about using it so I never have to dust my machine ever again... but seeing your vid thought it'd be perfect. Not knowing if it has any properties that'd inhibit its magnetic something-or-other.

Electorials (author)  Tolderian3 years ago
Thanks, I'll try it ;)
Electorials (author) 3 years ago
Would anyone maybe try to make this at home, with different types of oil?
I would like to see the results :)
gomiboy3 years ago
If you skip the step where you separate the magnetic band from the plastic band and just burn the tape as it comes out of the cassette, would that work? It voids the "harmful chemicals" part, since I'm sure inhaling the plastic fumes would be nasty, but I'm curious to know if you would still end up with a useable end product.
Electorials (author)  gomiboy3 years ago
I think the plastic would melt and you'd end up with a tough disc but maybe you can use it as a frisbee!
You can then deflect it's path with a magnet ;)
Kiteman3 years ago
Picky point: everything is chemicals. The magnetic tape, the vegetable oil, the air you breath.

Maybe you should say "without using any harmful chemicals"?

Electorials (author)  Kiteman3 years ago
you have a point there :) I changed it.