Ferrofluid magnetic Cores

[d3x0r]

For lack of anywhere better to post this also.

Was looking around following an interesting joule-ringer replication by lasersaber(http://www.youtube.com/watch?v=PoEXCweMxhk or http://www.youtube.com/user/lasersaber#p/u/3/glRuwV9IlaY ), who was saying his cores were metglas, which wikipedia has listed as 1 milllion times more permable than air; which I am beginning to doubt the legitimacy of, but anyhow, my first idea was to use a stranded iron core, but then I remembered ferrofluid, and I'm having a hard time finding useful information on the relative permeability of ferrofluid.
I did see an article where ferrofluid might be added to existing transformers; but they were still implying that they would keep the solid magnetic core(?)

Also wouldn't the MEG ( htp://www.youtube.com/watch?v=F3bVUr5nHaM ) benefit from sucure a core?

[d3x0r]

I have some ferrofluid.  I ran to the hardware store and bought some 3/8" ID 1/2"OD plastic tubing, and a plastic T connector.  I wound a stranded iron core (not sure how iron it may be a steel of some sort) that was approx 3/8" diameter, which I then chopped in two.
I rolled some coils that were about 7m of 24 gauge wire about 1/2"ID and about 3/4" long.  (fairly sloppy) but good enough to use my signal generator to trigger one coil and scope the other, with one side of everything grounded, could pick up something resembling the signal, at a distance that would be beyond a capacitive coupling (ie. removing the core removed the signal also)  I tried a couple other solid cores that were just bars (but they were a bigger diamter also.  (Oh I used a peice of the plastic tubing around the core to space it within the coil about where the ferrofluid path would be). 
So; fairly confident in my benchmark, I moved the coils to a length of tube that was approx the diameter of the stranded iron wire core, joined them together, and filled with ferrofluid to the top.  fairly certain I had most of the air worked out (maybe not, could have been bad air bubbles).  and I got much less signal transfer through the core.
1) maybe the density of iron in ferro fluid is much less than that of iron wire (molarity?)
if 1) maybe I should try and evaporate some of the mineral spirit off of it?
Alternatively, maybe I should work to process it to be some sort of gel?  One of the cores that lasersaber(?) mentioned was it was kind of rubbery when he took the plastic case off of it?