Cleaning old bells

[Carl Scott Zimmerman]

Photos in RW articles about bell restoration projects almost always 
show that the bellfounders and bellhangers respect the antiquity of 
the bells.  New fittings are cheerfully bright with new paint, but 
the patina of the bells is undisturbed.

Unfortunately, that respect for antiquity is not widespread in 
America.  The major maintenance firms seem bent on persuading their 
customers of the "need" for sandblasting or other harsh methods of 
polishing to make old bells "look like new."  I find that practice 
deplorable, and speak against it when I can, sometimes comparing it 
to making one's grandmother get a facelift so that one doesn't have 
to see her wrinkles any more.

But I'd like to have some more specific recommendations to make to 
those who are considering renovation projects.  Hence this message, 
with the following question:

What methods do English bellfounders and bellhangers use to clean 
grease, bird droppings or other forms of dirt from old bells without 
disturbing the patina significantly?

Thanks in advance,

Carl