Dried up Ferrofluid?


What causes ferrofluid to dry up?  Heat, usage, age?  Is there a usual shelf life, as in, do most 15-20 year old tweeters that originally used ferrofluid, need new ferrofluid?

How is it checked, where is it bought, is the replacement generally the same from tweeter to tweeter?

Thanks ahead of time for any info regarding this!  I figure that there are quite a few good speakers out there that are getting up there in age so this may be something I’ll want to learn to do!
128x128b_limo
Im a prep’er, lol.  You may have cases of water, I’ll have cases of ferro fluid.

Its just that a bunch of speakers I look at buying are getting up there in age.  Some of them are 20 years old...
I went through the exercise about a year ago with some old soft dome Scanspeak tweeters.  I did watch a few you tube videos explaining how to disassemble the tweeter, clean out the old fluid and install new fluid.

It turns out my Scanspeak classic tweeters were much easier to disassemble than the tweeters on you tube.  Once disassembled, you use blotter paper and I think alcohol to soak up and clean any remaining old fluid in the tweeter "well" (my word) and then buy and install new fluid.

I spoke with Madisound and they thought it would be ok to not replace the fluid at all, and I believe (might not remember correctly) they said many new tweeters don't use the fluid at all. I ran them a little without fluid but ultimately installed the fluid and like the sound better.
If you are interested in getting your hands dirty, consider a new kit instead. Built the whole thing from scratch. :)
Erik, I asked you a while ago, but you never answered.  I read your paper on a pair of speakers you built, but asked how many pairs you have actually assembled?  Is it the one pair, really just curious, I am not handy and wouldn't dare try.
@jetter

I answered you. Go back and look.

But truth is I have never built cabinets. The cabinet for the SNR-1 was custom built by Lee Taylor of Taylor Acoustics.

The other 2 models used kit boxes. In all cases the part selection and schematics were my own.