The jewelers stuff is just alum. Every generation seems to forget the trick
and someone capitalizes on this by putting a bunch of alum in little
bottles.

They sell a bunch and disappear before the old timers can stop laughing.

There was recent reference here to the use of alum (septic pencil), but I
believe that was for use for a tap snapped off in aluminum.
I could move the hole over and retap, but it would throw off the symmetry
of the piece - however if the worst comes to the worst.
Help!

Alum works fine on bronze.

Use a saturated solution. You have to keep it hot and the tap immersed. If
you can't do either, you are just gonna waste your time.

Paul K. Dickman

Alum, or Aluminum Potassium Sulphate, when added to water is Sulfuric
Acid.
Available in flooded cell auto batteries, and in the drain cleaner
section of some hardware stores.

Nasty stuff on skin or eyes.
I have no idea if it reacts with Bronze, but it does dissolve steel,
heat speeds up the reaction.

Dave