I had an old toner cartridge lying around, so I took it apart and emptied the toner into a jar. I had heard that one could make a ferromagnetic fluid using toner powder and oil, so I mixed a little powder with some kerosene that I had on hand. Turns out, kerosine does something wierd to the polymer part of the toner, and instead of becoming a solution, the toner powder coagulated into a rubbery mass that had a consistency similar to chewing gum.

When I put a powerful magnet from a hard drive next to it, the ball was attracted to it, which surprised me a little, as I had seen on wikipedia that toner had no magnetic components (any more) So, the questio is, Why is printer toner powder magnetic? Is it because carbon is paramagnetic?

Also, what happened to the polymer when kerosine was added?


A clarification- I think the polymer is a resin (based on what the kerosene did to it)

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    $\begingroup$ The toner might contain magnetite or iron powder. Both are magnetic. $\endgroup$ – aventurin Jun 6 '16 at 18:52
  • $\begingroup$ Some toner is magnetic but not all toner. Some was designed to be machine readable but that is far less common now. You cannot assume from one example that it applies to all toner as many people trying to make ferromagnetic fluids have found out. $\endgroup$ – matt_black Oct 2 '18 at 23:23

One of the major ingredients in modern printer toner cartridges (for laser printers) is magnetite, Fe3O4. It is used a charge control ingredient, known as a triboelectrification agent. 'Tribo' comes from the Greek meaning 'to rub' (carfeul if you google that one), and essentially refers to the creation of static charge through friction. This is required to have the printer particles stick to the paper. You can read about triboelectrification here. Magnetite, of course, is magnetic, and this is why your toner can produce a ferromagnetic fluid.

Other ingredients in toner cartridges include waxes, polymers and pigments. Many formulations are water or alcohol based and the toner is actually prepared as an emulsion which is filtered and dried. In order to get this material dissolved into kerosene, you probably need to add an emulsifying agent. Oleic acid is commonly used to achieve this, as it is a long chain acid that has both polar (hydrophilic) and non-polar (hydrophobic) properties.

  • $\begingroup$ So what is the kerosene doing to the polymer? When I added kerosene to the powder it pretty much instantly clumped up into a gummy mass. Is the kerosene polymerizing the resin? $\endgroup$ – Warpspeed SCP Jun 7 '16 at 3:26
  • $\begingroup$ Unlikely to be polymerising. More likely it is simply coagulating, but there will be some components that have partial solubility in kerosene; waxes and and some resins. Overall, it is probably a water based or hydrophilic formulation. $\endgroup$ – long Jun 7 '16 at 8:30
  • $\begingroup$ by water based, do you mean like acrylic paint (which becomes water insoluble when dried)? $\endgroup$ – Warpspeed SCP Jun 7 '16 at 9:03

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