Introduction: Ferromagnetic Fluid

Magnetic silly putty was pretty awesome, but it's time to take it to the next level with

ferromagnetic fluid!

Making your own ferromagnetic fluid (ferrofluid) is super easy, and it uses the same easy to get black iron oxide powder as the magnetic putty. The best thing about ferromagnetic fluid is that there's many ways to make it. Depending what medium you add to the oxide powder it will react differently; a low viscosity medium like water will allow you to play with magnetic fields with immediate feedback, a higher viscosity medium like mineral oil will suspend the oxide particles and create beautiful sculptures of magnetic fields. I'll show you how to make both.

Ready to get polarized? Let's make!

Step 1: Supplies

Picture of Supplies

Since we're working with paint pigment you'll need to protect your work surface, and wear protective gloves so you don't stain your hands.

Step 2:

Picture of

Add a small scoop of iron oxide powder to a clean and dry glass container. You won't need much, about one half scoop for a 6oz (175ml) container.

Fill remainder of container to the brim with water. Don't worry about any dry pockets of powder after the water is poured on top, the oxide powder will eventually be saturated with water.

Step 3: Seal With Caulking

Picture of Seal With Caulking

Playing with ferromagnetic fluid is super fun, spilling it isn't.

To protect against eventual spills a bead of silicone caulking is added to the threads of the container and the lid tightly screwed on, creating a waterproof seal. The container was left upright to cure for a few hours.

Step 4: Add Magnet

Picture of Add Magnet

After the caulking has cured you're ready to play with your container of ferromagnetic fluid. Bring a magnet close to the container and watch the magnetic field become visible as the iron filings attract in the water medium.

Try hovering the magnet at different distances away from the container to create different visual effects, or try dragging the magnet around the container and watch the filings pile up.

Step 5: Ferromagnetic Fluid With Oil

Picture of Ferromagnetic Fluid With Oil

Another great medium to display a magnetic field is in a neutral oil. This type of ferromagnetic fluid makes a blob-like creation with similar properties for viewing the magnetic field.

Along with the black iron oxide you'll need mineral oil and a thin plastic dish to hold your liquid (I used a lid from a take out container).

Step 6: Add Oil and Mix

Picture of Add Oil and Mix

Scoop black iron oxide powder onto your dish and pour mineral oil over, stir until mixed completely and there are no lumps.

Step 7: Introduce Magnet

Picture of Introduce Magnet

Place magnet underneath the dish and watch as the viscus ferromagnetic fluid takes the shape of the magnetic field.


Have you made your own ferromagnetic fluid? I want to see it!
Share a picture of your version of this project in the comments below and be awarded a 3-month Pro Membership



osterac made it! (author)2015-10-25

Thanks for the instructable!

I mixed the black iron oxide with some olive oil and suspended it in rubbing alcohol. For the jar I got a jar of Capers and emptied it out - don't think I'll be eating the Capers though.

政蓝 (author)osterac2017-02-04

How many iron oxide and oil u put????

政蓝 (author)osterac2017-02-04

Success or not

mikeasaurus (author)osterac2015-10-26

The mix seems to be perfect. Glad this worked out for you!

Thanks for sharing a picture, enjoy the Pro Membership!

AdamC221 (author)2016-10-06

Will using a plastic container yield different results?

mikeasaurus (author)AdamC2212016-10-07

Should be the same, though a plastic container might get scratched over time from the particles and become hazy.

Eli9232 (author)2016-08-04

I do believe you mean to say "Mesmerizing" I probably will memorise that recipe, (It truly is fascinating) but I dont think thats what you meant.

dcq32 (author)2014-11-02

What is the procedure for the disposal of the fluid

SherylinRM (author)dcq322016-07-17

If you spread it around the base of a maple tree the leaves will turn a brighter red in the fall.

They love iron so long as you dilute it a lot. Say mix what you have with a gallon [or four liters] of water :)

Just an idea :)

mikeasaurus (author)dcq322014-11-02

You want to dispose of it? I still have mine at my desk to play with.

If you must get rid of it, since it's just a small amount of iron pigment, you could dispose of it in dirt.

ryan422 made it! (author)2016-06-26

looks really cool thanks tons. sorry for low quality pictures I made both types.

mikeasaurus (author)ryan4222016-06-27

Nice job. You might want to put a lid on your fluid so it doesn't make a mess if you spill it!

ryan422 (author)mikeasaurus2016-06-27

I learned that the hard way lucky I wasn't wearing any good cloths.

asphalt (author)2015-08-27

asphalt made it! (author)2015-08-27

I used rubbing alcohol for my suspension medium.

mikeasaurus (author)asphalt2015-08-27

Whoa, that looks so clear. Thanks for sharing, enjoy the Pro Membership!

asphalt (author)2015-08-27

golab61 (author)2015-04-19

hi. I was wondering is there any way to make a magnetic paint so the surface covered by that paint acts as a magnet?

mikeasaurus (author)golab612015-04-20

Well, the iron oxide is a paint pigment. Maybe try and mix a higher concentration of the powder with a paint base and see what happens?

CrayfishYAY made it! (author)2014-12-24

I remember when I was in Alabama, I went outside & used a magnet to collect magnetic rocks. Then I spent long & tedious hours to finally get magnetic powder. I mixed the powder w/ vegetable oil, stuck 3 "sizzlers" under the plate, & this is the result:

mikeasaurus (author)CrayfishYAY2014-12-25

Wow, that's a cool story. I love that you had to find your own iron to make this. Thanks for sharing!

Enjoy the 3-month Pro Membership!

violingirl made it! (author)2014-12-19

Thanks for this great project.

mikeasaurus (author)violingirl2014-12-25

Thanks for sharing your version. I hope you still have fun playing with it.

Enjoy the 3-month Pro Membership!

Leei1337 (author)2014-10-30

How well would this work if I scaled it down? I am wanting one as a keyring so I've got something to fiddle with ?

ottermann (author)2014-07-31

Can you mix up a batch with the mineral oil, then put a small amount in a vial and fill the vial the rest of the way with more oil? If you do, does the 'blob' retain it's cohesion? Or does it dissipate?

mikeasaurus (author)ottermann2014-07-31

Excellent question!

While making this Instructable I experimented with a few different mediums to suspend the iron oxide powder; Alcohol, acetone, water, and mineral oil.

I found that the mineral oil was too viscus and suspended the powder making the fluid cloudy. Here's the picture of my results.

Hey Mike, is there any performance variance between the natural and synthetic Fe3O4? I know there is a large variance in particle size but wasn't sure if it was of consequence for this type of experiment. - Thanks in advance for your time and consideration.

ElectroFrank (author)mikeasaurus2014-08-05

Oil comes in many different viscosities which could be experimented with. Car engine oil would probably be too thick and dark. A light "sewing machine oil" might work well, or how about "baby oil" ?

Perhaps even your thick oil might clear if a magnet was left beside it for a while ? And in oil, would even plain iron filings work OK ?

THIS is almost a ferro magnetic fluid

GwydTUnusual (author)ottermann2014-07-31

That is the same exact thing I thought...Would it work?

laffinm (author)2014-08-13

Could it be possible to use fine shavings from a file to be used for this, or would they be too large?

Magitor (author)2014-07-29

This is not a ferromagnetic fluid....

Azzurro (author)Magitor2014-08-02

I agree. this is just ferromagnetic stuff in fluid.

Laral (author)Magitor2014-07-31

It is absolutely a ferromagnetic fluid by definition. What it is not is ferrofluid. There's a difference.

Magitor (author)Laral2014-07-31

Actually the word ferrofluid is portmonteau of the ferromagnetic fluid. A fluid wich has ferromagnetic property.

Laral (author)Magitor2014-07-31

Mere semantics. The word ferrofluid is in common use so it is well understood what it refers to. That's what both you and tallest are referring to. And, of course it's better than this but so what? Try making some…

suomy.nona.14 (author)Laral2014-08-01

the term 'magnetic powder suspension' is also in common use, and actually correct, unlike ferrofluid

Laral (author)suomy.nona.142014-08-01

Huh? Show me one reference that uses magnetic powder suspension and then use it in a sentence. What do you mean by "actually correct, unlike ferrofluid"? Sounds like utter nonsense to me…

tallest (author)Magitor2014-07-29

Agreed, I have the real deal; and this, while cool, is not the same. The real stuff uses nanoscale magnetite coated with a surfactant to prevent clumping, and is much thinner in consistency than the mineral oil stuff here. The particles of magnetite used in this instructable are too big and uneven, and without the surfactant the fluid won't move right when a magnetic field is applied.

This project could still be a good way to introduce kids to the basic concepts involved though.

MaggieS1 (author)2014-07-31

Hey! Could someone please tell me what this really is if it's not a ferromagnetic fluid/ ferrofluid? My knowledge in chemistry is pretty basic but I would love to show this to my classmates in school actually knowing what I'm talking about!

Also, does the water stay clear or will it get cloudy over time? Will it have the same effect in oil? And if I don't add anything to it?


jwhitley (author)MaggieS12014-08-01

Unfortunately, the title is a bit misleading. This is not actually ferromagnetic fluid, it is a ferromagnetic material (iron oxide) in a fluid medium (as Mike mentions in his comment here). A ferrofluid is usually made by using nanoparticles suspended in an oil. The entire medium moves in reaction to the presence of the magnetic field rather than just the ferrous particles. Unfortunately, making nano-scale, highly-round particles of iron turns out to be very difficult and expensive. It's also nearly impossible to get off of you because of the type of oil used. For an example of what it looks like and how it acts, see:

suomy.nona.14 (author)jwhitley2014-08-01

this must be the only correct piece of information in this whole instructible

mikeasaurus (author)MaggieS12014-07-31

It's ferrous powder in a fluid medium. It's an inexpensive DIY approach to visualize magnetic fields.

I've made a few, and the one sitting on my desk for 2 weeks is still clear. You should see my reply to otterman in the comments on my experiments with oil as the carrier in a jar (hint: oil works better on a flat surface as I show in Step 6-7 of this project).

I'd love to see your results!

MaggieS1 (author)mikeasaurus2014-07-31

Oh I didn't realize there were more steps! That is pretty amazing.
I'm already looking up where I can buy this. Thanks for the reply!

Laral (author)2014-07-31

Hey Mike, though you never answered my PMs, I see you went and bought the Fe₃O₄ from AlphaChem that I recommended. I have made liquid demonstrators like this with mineral oil, water, and alcohol, but I find that just containing the powder dry, in a sealed container works best. It allows more freedom of motion and awesome spikes and manipulations. I have also used, dry and wet, the really cool magnet powders, both alnico and NIB, from SuperMagnetMan. I find that dry works best and I prefer the alnico because it glistens and does not dust up the plastic like the NIB does.

avonborowsky (author)2014-07-30

Doesn't it get stain with time because of the water?

jcraig20 made it! (author)2014-07-30

This stuff is cool to play with especially if you have lots of magnets and kids and a place that you don't mind getting messy.

Verticees (author)2014-07-30

I like the GIFS you included to show its behavior! Awesome!

文邱 made it! (author)2014-07-30

I made it last year, but I add glycerin in the container.

Jan_Henrik (author)2014-07-29

:( "Chemicals" are not sold to germany, but nice project!

About This Instructable




Bio: I'm Mike and I make crazy things at Instructables HQ in San Francisco. Follow me and try a few of my projects for yourself!
More by mikeasaurus:Router Planer10 MORE Woodworking Tricks the Pros UseSliced Wood Coasters
Add instructable to: