[ttlsksky]

I tried to put the 'Ferrofluid' and the clear liquid in a large glass tank.
My glass tank was bonded with silicone.
However, silicon reacted with 'Ferrofluid' ('Ferrofluid' became sticky and hardened).
Perhaps 'Ferrofluid' seems to have chemically reacted with silicon because 'heptane' is the base.
What kind of glass glue can replace silicone?
Perhaps the epoxy is good, but it is not elastic.

[Enthalpy]

Or did heptane evaporate, leaving a thick residue from your ferrofluid? You could compare with the ferrofluid in a dish plate.

Elastic and sticking to glass, that's silicone. There would be more options with PMMA if it's compatible with heptane.