There are downsides to this method, the first being that a cracked ammonia
annealing furnace is not inexpensive. The second issue is that the hydrogen gas
will easily work into the sterling silver piece and find any cuprous oxide (Cu2O)
beneath the surface layer. The reaction produces water vapor, which is a much
larger molecule that cannot easily escape through the surface layer. The pressure
from the steam exerts stress on the grain boundaries and creates blisters on the
surface of the metal