VersaInk Versaink-Nano Magnetic Ferrofluid 100ml (VIMF-6697)

Most of the fluid is magnetic but it leaves an oily film behind that you cannot see through. I wanted to be able to keep it in a glass and show the kids but as soon as it is pulled to a portion of clear glass and then released it leaves behind black oil. Worked for a few minutes and then you could no longer see inside the glass. Would be happy to hear if there was a better solution to what I need.

Ive been woring with ferrofluid for a while and tried a couple of companies. But they always rust because of the iron, i just figured id try this one and it was litterally just ink