Burned Shellac was for over 100 years the only substance that  glued
anything to metal.  In players, it was used to seal valves, put lead
tubes into wood, brass nipples into wood, glue felt to metal as on some
grand hammer rails.  I have found it gluing felt onto piano pedals,
gluing metal fingers to pneumatic boards, felt to wood, I even suspect I
once found a keyboard bushed with it.

To remove it from the old location, use a heat gun and a cabinet scraper
or putty knife.  High heat is not necessary.  If it gets warm enough, it
will come off clean as a whistle.  I wish I had back all the hours I
spent scraping, gouging, and digging with all my might to remove it
before I learned about the heat gun.  Today it is still useful, as I do
not trust plastic glue that much, although I do use it for some things.

When normal finishing shellac gets too old, it tends to stop drying well
and you have to throw it out.  I normally mix up only what shellac I will
use from crystals and alcohol the day before I need it, but sometimes you
have some that sits around too long.  You can use this throwaway shellac
as burned shellac and its age will not matter.  Normal shellac and burned
shellac are two completely different chemical substances.  They are not
interchangeable, however, I have noticed that some players used burned
shellac as a finish on the inside of pouch wells and channels.

My method to make burned shellac is as follows:

Pour regular shellac of normal thickness into a shallow metal container
that can handle the heat.  I use a Tuna can or small saucepan.  I use a
small tin can (tuna) so I can throw it out when I am finished rather than
have to clean out a good saucepan.  I fill the pan about half full.  Have a
lid or a metal panel to put over the top to stop the burn.  Put the can on
a metal surface.  It is not going to be really hot but it will be too hot
to handle for a few minutes.

Light the shellac with a match or Bic.  Using a metal rod that is long
enough, stir the burning shellac until it is ready to extinguish.  Let it
burn until it darkens without getting black. (Not quite as dark as the
stuff you scraped off of the lead tubing in your player piano.)  You will
notice that it begins to smell like a candied apple as the natural sugars
in the shellac caramelize.  Take out the stirrer and put the lid on to
exclude air and put out the fire.  Let it cool, pour it into a plastic
squeeze bottle. (Clear honey bottle) and make more if you need more.
Sealed in the squeeze bottle, it will last virtually forever.

I removed a pipe organ a few years ago that had originally been tubular
pneumatic.  That means it had a lead tube the size of your finger that
went from the organ to the console for every note on the chest primary.
The organ had been installed in 1910, electrocuted in 1970 and yet I
found a VERY old whiskey bottle under the chest full of burned shellac.
Since they used the stuff to install the lead tubing into the wood
spreaders, and the bottle and its cork was the same vintage as the organ,
I suspect it was left by the installers from Hook and Hastings.

Believe it or not, the burned shellac was still good and I have used it
successfully.  I think 80 years is nearly forever for a glue shelf-life to
last.

D. L. Bullock  Piano World St. Louis