Hi, I wondered about this stuff so I checked out their web site.  Lots
of interesting stuff there.  But I'm not sure what use this stuff would
be to restore a piano or anything else assembled with hide glue.

In the description it says "The nice thing is that it won't seep into
glue joints, so you can use it around a bridge or neck reset or anything
like that."  So, if it wouldn't seep into a glue joint, what use is it?

I suppose you could use it to clean up hide glue or white glue from a
surface, but you can clean up hide glue with water.  At this price,
it's even more expensive that bottled water.

Regards,
Craig Smith