Craig Smith wrote, "So, if it wouldn't seep into a glue joint, what
use is it?"

Luthiers commonly steam joints open and then need to remove the glue
residue without taking any wood away, so sanding is not an option.
As Craig notes hide glue is usually easy in this regard, but the
"what good is it" may come in its promise to also remove Elmer's Glue
and Titebond.  As in mechanical instrument work, these adhesives are
also the scourge of the stringed instrument repairperson.

Does it work?  I've no clue, but most StewMac products are at least
worth a try.  The pricing may reflect the fact that it's targeted to
small instruments, not pianos.

Cheers!
Roger Wiegand
Wayland, Massachusetts, USA
http://www.carouselorgan.com/