Why is my silver turning cloudy after annealing at 600C when I
anneal in Nitrogen?
I don’t know if anyone has answered this question or not. However,
there may be several reasons and forgive me if I make assumptions
that are not true, I am just trying to cover most of the problems
1: The annealing furnace hearth or chamber may not have been purged
of all the air or moisture.
The Nitrogen used could be contaminated with air and moisture.
Of course, the cool down rate in the normal atmosphere can create
surface discoloration, as well.
As far as the “dull” anneal problem, the chamber also must be
totally sealed or the “inert” atmospaher gases must be pure and
exhibit a positive chamber pressure where oxygen and/or moisture
cannot get to it. Cool down has to be in the in the inert
These are some of the most frequent problems I personally have seen
Also, the American Society of Metals, Metals Handbook, 8th Edition,
Vol. 2, HEAT TREATING CLEANING AND FINISHING, page 306, depicts the
annealing curves of Precious Metals including Commercial Fine Silver
and Sterling Silver.
The tell tale story on the Commercial Fine Silver is the Percent
Elongation curve where elongation is meaured and plotted against
Annealing Temperature. This curve shows where the Fine silver
increases % elongation from approximately 10% at 400 F (NOT “C”) to
approximately 50% Elongation at 600 F. The curve appears almost
vertical between those temperatuires. This major change in
elongation after exposure to 600 F strongly suggest, after exposure
for a period of time (you have to dertermine that length of time
experimentally for your application), you can obtain nearly full
anneal. Apparently, you do not have to get into the RED heat range
for annealing silver.
The same is true for the Sterling, except the rapid change in %
elongation is experienced between 500 F and 700 F.
I, personally, use both flame and furnace annealing practices and
follow the “pickling advice” unless I am doing quantity, which very
seldom. Oh! I pickle straight from the furnace to the pickle (while
the piece is HOT).
I hope this helps. The experimental approach for your specific
application certainly is recommended and the above is a
I hope this helps.
Metallurgical Engineer, P.E.
Amatuer Jewelry “player”