Ferromagnetic Fluid




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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!

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Step 1: 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:

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

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

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

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

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

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


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37 Discussions


Question 3 months ago

how much water do you need to make it what is


2 years ago

Will using a plastic container yield different results?

1 reply

Reply 2 years ago

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


3 years ago

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.


4 years ago

What is the procedure for the disposal of the fluid

2 replies

Reply 3 years ago

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 :)


Reply 4 years ago on Introduction

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.


4 years ago on Introduction

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

1 reply

Reply 4 years ago on Introduction

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?


4 years ago

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 ?


5 years ago on Step 7

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?

5 replies

Reply 5 years ago on Introduction

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.

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 ?


5 years ago

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