Pretreatment of the glass by: 1) soaking it overnight in a strong solution of KOH in ethanol or 2) by coating the inside with Scotchgard® spray and drying will help the ferrofluid drain more rapidly
or you could try applying a film forming sealant such as they use on concrete garage floors
quoted from " http://www.everythin...oor-sealer.html "
FILM FORMING SEALERS: These form a protective film on the surface of the concrete. This thin film blocks water and harmful chemicals from being absorbed into the concrete.
Film forming sealers are great for decorative concrete because they will darken and highlight the colors in the concrete. The film or clear skin it leaves on the surface will be slippery when it gets wet. Non skid additives can be used to keep the surface from being too slippery.
There are three types of film forming sealers, Acrylics, Polyurethanes, and Epoxies. Acrylics are the easiest and least expansive to use. A good water or solvent based acrylic is all you need for a very good, easy to apply garage floor sealant.
Acrylic floor sealers can be applied with a pump up sprayer or paint roller. They usually dry within an hour and come in different sheen levels, if you like a shiny gloss look this is the sealer to get.
not very scientific i know , but neither was the lightbulb when it began cheers!
p.s. after treating the container, make sure to fill it with the desired medium first , then add the ferrofluid (add just under the surface tension) no air pockets allowed
i have seen windex used but i am not sure if it would eventualy break down the ferrofluid's "carrier fluid"
