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Heat Hardening Silver


#1

Dear Orchid-Members! Does anyone know something about heat-
hardening
silver and which alloys are to be used for the process? Thank you in
advance

Sigrid


#2

Heat Hardening Metals Sterling Silver

Sterling silver can be harden dramatically by firstannealing and then
submitting it to a one hour heat treatment at 600 F. The higher the
preliminary annealing temperature (up to1350 F) the harder the alloy.
However,it’s dangerous to quench sterling at temperatures above 1200
F. Therefore, itis recommended to follow this proceduRe:

  1. Heat (anneal) the item to 1200 F

  2. Quench immediately

  3. Place in a furnace preheated to 600 F and heat soak forone (1)
    hour.

  4. Bench cool You can use an anti-oxide of boric acid and alcohol, but
    isdoes not help that much in reducing the oxidation.

Gold Many karat gold’s can be hardened through heattreatment. The
degree to whic h an alloyis hardenable depends on its non-gold
component. The type of alloy will depend on the final hardness.

  1. Heat(anneal) the item to 1100 F - 1200 F"

  2. Quench immediately

  3. Place in a furnace preheated to 600 F and heat soak fortwo (2)
    hours

  4. Beach cool You can use an anti-oxide of boric acid and alcohol, it
    willhelp some what i n reducing any oxidation.

Platinum Platinum will respond to a hardening procedure over a
broadrange of temperatures. This techniquewill yield an increased
strength about 70% from

fully soft. This can be applied to either soft or hardenmetals

  1. Heat item to a medium orange color about 700 C

  2. Allow to cool in the air until no color can be seen

  3. Then quench in water

  4. It is a good idea to repeat this process if a torch isused

another way

1. Heat item to 500 C for 30 minutes
2. Allow to cool in the air until no color can be seen
3. Then quench in water
4. This will harden the metal approximately 3X

#3

McCreight’s book says that you can heat harden sterling silver by
holding at 620F for three hours, then quenching?

(a) don't quote me on the temperature
(b) don't quote me on the time
(c) don't quote me on the quenching 

:-). It might be air cooling, and it might be a lower temperature for
a lower time. I need to go look it up as I’ve only done it once.

Each of my books has a different approach for heat hardening silver,
I don’t know which may be better because I’ve only done it once (via
McCreight’s method) and it seemed to work out pretty well.

  • darcy

#4

Hi Sigrid, I think this has been covered pretty exhaustively in the
past… check the Orchid archives… I believe a soak at 650 deg. F.
for 2 hours or more… but check to be sure.

I am writing to add in the June 2001 issue of SNAG (Society of North
American Goldsmiths) News there is a Tech News article by Jeff
Herman, executive director of the Society of American Silversmiths
regarding Argentium® sterling silver. This is apparently fine silver
alloyed with germanium, as opposed to copper, which provides some
interesting characteristics. The article goes on to discuss working
properties, fabrication and forming, casting, annealing and soldering
and so on, including heat hardening.

What I found very interesting is that this new sterling alloy can
apparently be heat hardened at 450 deg. F., which puts it in the range
for any standard kitchen oven!

According to the article, there is limited availability of sheet to
SAS artisan members, and plans are underway to find a U.S. fabricator
for mass production.

Here’s a URL to an updated version of the article I founds on the SAS
Web site:

http://www.silversmithing.com/1argentium.htm

All the best,
Dave
Dave Sebaste
dave@sebaste.com


#5

in an oven, hold sterling at about 575-625 degrees for 2 hours. Then,
turn the oven off and let cool slowly (4-8 hours, or overnight).

When done properly, you can get a spring hardness to normal sterling.
Also, suggest leaving flux residue on the piece to prevent fire
scale, or putting a small block of wood in the oven to remove any
oxygen.

When done, do NOT anneal. This has to be the last torch or heat
involved operation you do on the metal, i.e., no soldering afterwards
or you lose the hardness.

Mark Zirinsky, Denver


#6

Sterling silver anneals quickly at 800 C. If it is held too long at
this temperature or is heated hotter the grain crystals grow and the
material becomes brittle and unuseable. Annealed steling then can be
age hardened at lower temperatures 200- 300 C. At 200 C it will reach
its maximum hardness in about 8 hours. At 250 C it will reach its
maximum hardness in about 1 hr and then start to soften again. At 300
C it will reach its maximum hardness in about 30 minutes and then
start to soften again. The best aging temperature for both sterling
(92.5 % Ag) and 93.7 Ag is 250 C (482 F) for about 2 hrs - no more.
This is achieveable in a normal kitchen oven. Time and temperature
data is from “Precious metals- science and technology”.

Jesse