Since fish-bladder isinglass is, I think, water-soluble and mica is not, I
would guess mica for carriage windows and fish-bladder isinglass for
egg preservation, probably along the same lines as sodium silicate or
water glass (this is a guess).  Mica was historically used for furnace
windows and I would assume for other applications.  Get in touch with a
Smithsonian history of tech person.  Ellen Lawrence.