Can You Make Your Own Magnetic Ink?
Here [Catarina Mota] is showing off a ring of magnetic ink printed on a piece of paper. It's strong enough to hold a disc magnet in place when the paper is raised vertically. By mixing it with acrylic medium in a vortex mixer you end up with a homogeneous ink. ...
Pour a bit of vegetable oil into a shallow dish, just enough to make a thin film across the bottom. Pour iron filings into the oil and mix the two until they have become a thick, sludge-like material. This is your ferrofluid!
Making Ferrofluids - MagLab
If you tried to make a MICR Inkjet cartridge, all the magnetic particles would simply settle to the bottom, and you'd be left with regular ink. So the right kind of ink simply is not available. ... It is even possible to buy MICR toner cartridges specifically for check printing.
Laser Printing, Magnetism, and You: How Self-Printed Checks Affect ...
Ferrofluid is a liquid that is attracted to the poles of a magnet. It is a colloidal liquid made of nanoscale ferromagnetic, or ferrimagnetic, particles suspended in a carrier fluid (usually an organic solvent or water).
Ferrofluid - Wikipedia