JAY!!! I **hope** you read this before tomorrow! Please remove
the heads from the alcohol right now... it is unpredictable what
long-term immersion in 91% isopropanol will do to a head assembly..
but I doubt anything good.
It is possible to soften and dissolve the coil binders, and
possibly to delaminate the magnetic core... and at the least to
impregnate the coils with alcohol, which will then be released as a
vapor or liquid contaminant over time... maybe carrying goo from the
stack.....
I hope that nothing evil comes of this... but overnight soaking
in **anything** is >not< the way to clean up magnetic heads.
Hoping for the best..
John