Hardening sterling silver

Jewelry Discussion
1

I have fabricated a pickle fork from sterling that was made from
rolled and then annealed sheet. The last annealing left it soft and
it remains softer than desired after the various fabrication
operations.

I can work harden the piece with a Delrin or Rawhide mallet but fear
damaging the surfaces.

How is the best way to harden such a piece?

Thoughts ?

2 
How is the best way to harden such a piece?

Does it have any solder on it? If not it is a perfect candidate for
precipitation hardening. Heat it to 1370F with good flux protection
(this is called solution annealing). Then quench it. After this heat
it to 550F for 1 hr(this is the precipitation or aging part of the
process). It will become quite hard. If it has solder joints then I
would just do the second part and heat it to 550F for 1 hr. It will
get quite a bit harder but not as hard as is possible on the
solution annealed material.

James Binnion
James Binnion Metal Arts

3

Hello Ben, Google or check on articles on Orchid on heat hardening,
that how you do it.

4

Ben- Tumble it in stainless steel shot.

Jo Haemer
www.timothywgreen.com

5

Ben,

I would try to use a vibratory tumbler with stainless steel shot for
4- 5 hrs. This will at least work harden the surface of the silver.

Chris R.

6 
Tumble it in stainless steel shot.

Im afraid that tumbling is given way too much credit for hardening
items. The hard layer that tumbling produces is only a few
millionths of an inch thick. Even light polishing will remove it.

James Binnion
James Binnion Metal Arts

7

I accidentally age hardened some sterling and now am having a hard
time annealing it. Despite repeated heating to 1300-1450 in a kiln
for a period of time, parts of the sheet remain springy while most
are soft. In addition, it is deeply fire stained. Any clues? Scrap
and start over?

8

You don’t mention the size of the fork, or the metal gauge, but one
purpose of annealing is to soften metal, so not surprised. If you
have a tumbler and it fits, try using that for approx. 30 minutes.

Mary Partlan
White Branch Designs

9 
I accidentally age hardened some sterling and now am having a hard
time annealing it. Despite repeated heating to 1300-1450 in a kiln
for a period of time, parts of the sheet remain springy while most
are soft. In addition, it is deeply fire stained. Any clues? Scrap
and start over?

Unless you have taken very careful precautions to protect the
sterling from oxygen while in the kiln you most likely have managed
to oxidize all the copper in the alloy. This will ruin the alloy as
the the copper oxide cannot be returned to copper metal and it will
remain quite hard. Annealing sterling in a kiln requires that you
totally block the oxygen from the sterling this will require more
than just flux as the time in the kiln will exceed the fluxes
ability to absorb oxygen and oxides. You need an oxygen barrier or
controlled atmosphere of some kind.

James Binnion
James Binnion Metal Arts

10

James,

Does it have any solder on it? If not it is a perfect candidate
for precipitation hardening. Heat it to 1370F with good flux
protection (this is called solution annealing). Then quench it.
After this heat it to 550F for 1 hr(this is the precipitation or
aging part of the process). It will become quite hard. If it has
solder joints then I would just do the second part and heat it to
550F for 1 hr. It will get quite a bit harder but not as hard as is
possible on the solution annealed material.

This is very interesting and I wasn’t familiar with this method of
work hardening. Does this method work with other metals or just the
annoyed properties of Sterling. In addition, would this apply to
Metal Clays? If so, which ones?

Thanks for the bounty of
Holly

11 
This is very interesting and I wasn't familiar with this method of
work hardening. Does this method work with other metals or just
the annoyed properties of Sterling. In addition, would this apply
to Metal Clays? If so, which ones?

Only certain alloys will do this, sterling silver (standard
silver-copper alloy uses the temperatures and times I mentioned but
Argentium will do this also with somewhat different temperatures).
The metal clays I know of will not harden this way as they are either
pure metals or alloys that do not exhibit this behavior or in the
case of the new sterling clay they are mixtures not alloys so the
copper cannot be totally dissolved into solution because it exists as
discrete particles rather than a homogenous alloy. Some gold alloys
will harden from heat treatment but with a different underling
mechanism and different process parameters. And it is not work
hardening but heat treating, work hardening implies cold work.

James Binnion
James Binnion Metal Arts