I'm guessing this perfect storm of conditions is what started the whole ammonia on brass issue:
Season cracking[edit]
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Cracking in brass caused by ammonia attack
Brass is susceptible to stress corrosion cracking,[35] especially from ammonia or substances containing or releasing ammonia. The problem is sometimes known as season cracking after it was first discovered in brass cartridges used for rifle ammunition during the 1920s in the British Indian Army. The problem was caused by high residual stresses from cold forming of the cases during manufacture, together with chemical attack from traces of ammonia in the atmosphere. The cartridges were stored in stables and the ammonia concentration rose during the hot summer months, thus initiating brittle cracks. The problem was resolved by annealing the cases, and storing the cartridges elsewhere.
I agree that using a few drops of Brasso in tumbling media won't do any harm. I'll continue to use the NuFinish & keep the Brasso for polishing the bric-a-brac.
Interesting article.
Ammonia is used in some copper remover solvents. There are different strengths! of ammonia. 5 to 20% or more.
It certainly can damage brass and other things, all depends on what percentage and for how long.