I recently decided to make my own ferrofluid toy to play with. I built a sealed enclosure at my local fablab, and the end result was perfect. It worked just like in the videos you see online, and I couldn't have been more pleased.

But then, after a week or so, I noticed that the fluid was moving a bit more sluggishly, and not long after that, it would barely react to the magnet at all. Now when I try to play with it, I have to press a big magnet right against the surface, and then the "fluid" moves completely uniformly -- less like a fluid and more like a big black rock.

The only thing I can think is that maybe the suspension fluid I used had a gradual drying-out effect on the ferrofluid. When I was originally building the thing, I did some googling to find out how best to do it all, and I found an old post on this very forum, suggesting the use of isopropyl alcohol, so that's what I used. I also used the same type of ferrofluid as the OP in that thread.

So would a different type of suspension fluid keep it from hardening like this? Or am I wrong about the cause? The only other thing I can think of is that maybe it's because there's a little air bubble in my enclosure. It can't be any external factors, because it's sealed completely airtight.

Any ideas? Thanks!

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    $\begingroup$ The manufacturers of the ferrofluid actually provide a phone number. It may be a little old-fashioned but you can always try calling them and asking them if the solvent you used is incompatible. $\endgroup$ – Buck Thorn Jul 26 at 18:44
  • $\begingroup$ How about I don't have to click on a link, where I can then guess what other link you mean, to find out what you did? ;-) $\endgroup$ – Karl Jul 26 at 19:02
  • $\begingroup$ Sorry — let me clarify: I’m using FerroFluid EFH-1 by FerroTec - amazingmagnets.com/show-decimal-ferrofluid-0250.aspx $\endgroup$ – Explodey Jul 27 at 22:12

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