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
Hey there b-limo,
I went thru this with my Kef Reference 104/2's recently, so I thought I'd add my two cents' worth. First, kudos to you brave diy'ers, I hope you all succeed. I took my Kefs to a trusted repair guy and he told me the ferrofluid had dried up - then led me to Midwest Speaker Repair for a pair of new tweeters, which supposedly have specs close to the original, and some say sound better. They were $60 each, I had them installed and the sound is really good. (Had to also rebuild the woofers, common with this mid-80s model).
Contact Bill Legal at Miller Sound in PA if you want someone to do them for you,

Happy Listening.
Bill is excellent and highly recommended. Just rebuilt one of the acoustic couplers from one of my Vandy 2CE Sig’s. Very very reasonable and a great guy.