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Questions and answers about ferrofluid

Table of Contents

What is ferrofluid?

Ferrofluid is a black ferromagnetic liquid that strongly reacts to magnetic fields. Depending on the strength of the magnetic field and its distance to the ferrofluid, intriguing patterns and many uniform-looking peaks are formed (a so-called ferrofluid hedgehog). There are different ferrofluids on the market, oil-based ferrofluids and fossil fuel-based ones. The ferrofluid in our assortment consists of oil as a carrier substance and a large number of ferromagnetic particles (magnetite, iron or cobalt). These particles have a diameter of only a few nanometres. And that’s what makes it so fascinating because a nanometre is one-millionth of a millimetre, i.e. 0,000001 mm!

Other interesting characteristics:
  • Working temperature: -20°C – approx. 130°C
  • Boiling point: > 250°C
  • Autoignition point: 180°C
  • Freezing point: -50°C

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How does ferrofluid work?

There is more going on in the black liquid than meets the eye. The reason for these characteristic peaks of the ferrofluid is a complex interaction of different forces.
We’ll try to explain it in a simplified way: To ensure the iron particles float around freely in the liquid and do not settle on the bottom, a certain substance, a so-called surfactant, is added to the solution. The iron particles are coated with this surfactant. Without it, the iron particles would clump together. It also holds the particles and the oil together. Ferrofluid is a viscid substance; it is more viscous than other liquids. When a magnet is held to the ferrofluid, the viscosity prevents the iron particles from separating from the carrier liquid. On the one hand, the iron particles are attracted by the magnetic field while, on the other hand, the surfactant simultaneously pulls the particles back into the viscous carrier liquid. Since the iron particles are repeatedly attracted by the magnet, the characteristic peaks form.

Why was ferrofluid developed?

Ferrofluid was developed in the 1960s by NASA scientist Steve Papell. He was looking for a way to direct the liquid fuel from rockets to a fuel pump in the engine despite the prevailing weightlessness in space. This gave rise to the idea of developing a ferrofluid fuel that could be drawn into the pump using magnets. However, ferrofluid did not become the established solution for this purpose.

What is ferrofluid used for?

Ferrofluid is ideal for experiments and to make magnetism visible. That is why this ferromagnetic liquid is often used in schools to better illustrate facts such as magnetism during physics lessons. But ferrofluid is also often found in technology, for example in loudspeakers, as well as in industry and medical engineering.

Please note: The ferrofluid from our assortment is not suitable for use in tweeters and loudspeakers, as this ferrofluid dries out quickly when exposed to air. This will damage the speakers and render them useless. Our ferrofluid is only suitable for demonstration purposes and experiments.

What is the shelf life of ferrofluid?

Ferrofluid can dry out after a certain time, and the shelf life depends on several factors. The carrier liquid of our ferrofluid M-FER-10 evaporates if the liquid is exposed to the air for too long. It is a process that is highly temperature-dependent. At room temperature, the concentration will change within a few months. This affects the distribution of the iron particles in the carrier substance and leads to partial sedimentation, i.e. settling of the iron particles. However, if the ferrofluid is stored in a sealed glass container, it can have a shelf life of up to ten years.

Is ferrofluid toxic?

Ferrofluid is based on hydrocarbons. The composition is similar to motor oil. So ferrofluid is safe but should not be ingested or inhaled. It can also cause severe eye irritation. Therefore, when using ferrofluid, be sure to protect yourself by wearing protective clothing, gloves and safety glasses. The ferrofluid from our assortment will not give off any toxic fumes as the substances contained within dissipate quickly.

How do I remove ferrofluid stains from the skin and clothing?

If ferrofluid gets on clothing, it will be impossible to remove the stains. For experiments, wear protective clothing or old clothing that can get dirty. Ferrofluid will cause stubborn stains on the skin as well. Be sure to also wear gloves and safety glasses when using ferrofluid.

How do I dispose of ferrofluid?

The composition of ferrofluid is very similar to motor oil. Therefore, dispose of ferrofluid as hazardous waste at the municipal collection point just as you would with motor oil. Small amounts can also be disposed of in the household rubbish. To do this, fill the ferrofluid into a tightly sealed plastic container or soak it up with paper towels.

Application examples

Ferrofluid makes it possible to create fantastic sculptures. In the video, screws were used. The ferromagnetic liquid has also been used for many great projects. And it remains a hit with our customers for magnet applications. Here you can discover a selection of interesting customer projects:

Ferrofluid in water

If you add a few drops of the ferromagnetic liquid to a container filled with water and hold a strong neodymium magnet next to it, you can observe very clearly how the ferrofluid behaves. However, if you use pure tap water, an oil film will form on top of the water due to the oil components of the ferrofluid. The solution: Add table salt to the water. Learn how to do this in our customer project Ferrofluid in a glass.

Other fascinating projects can be found in our magnet applications on the topic of ferrofluid.

Safety tips

When using ferrofluid, always wear long-sleeved protective clothing, gloves and safety glasses. In case of contact with the eyes, rinse with water for up to 15 minutes and seek medical advice. In case of contact with the skin, rinse immediately with plenty of water and soap. Ferrofluid should not be ingested and is highly flammable.