I have a bunch of strong magnets from old hard drives and I am thinking hard how this could finally be a good use of them. But the tube is opaque, so I can't see how I can make a toy out of it.
I guess I have to buy a copper tube to find out.
I guess I have to buy a copper tube to find out.
Some commercial products were Magview, Magcheck, Ferro-see, and Sprague-Mag. I don't know if any of these are still available.
The spray is iron powder suspended in a fluid (like trichlorotrifluoroethane) that evaporates rapidly and leaves magnetic particles oriented according to the magnetic field. The pattern can be made permanent by spraying with a fixative or hairspray, or lifted with cellophane tape.