Can I heat-harden sterling silver with ruby in finished pendant?

Gem Related Discussion
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I make jewelry for fun and I recently made a pendant with sterling half wound wire as a mount for a ruby. The ruby is not high quality by the standards of the trade but I like it.

The problem is that when working the wire, it’s become too soft and I fear it won’t hole the stone securely if it gets banged around or flexes. Ordinarily I’d harden the wire first and then minimally shape, but I got a bit excited about the shaping midway through the process and i’m tweaking it, the wire got softer.

One thing I read is that sterling can be heat hardened (it’s beyond the point of work-hardening without starting over. Since the stone is already mounted, I don’t want to unmount to harden if I don’t have to. So my question is can I hear harden the silver with the ruby?

Note; the ruby not heat treated which is one of the things i like about it, and although at best, my oven is won’t exceed about 600 degrees F, so I don’t think that will change the stone, but ai could be wrong on that. Any suggestions would be much appreciated.

Thank you!

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To answer the question you posted… :slight_smile:

It would be very risky to heat-harden (tempering) the silver with the stone in-place. Corundum is still prone to thermal-shock.

The best options:

  1. You can harden the metal using a burnishing tool to “work-harden” the wire, if the stone is already mounted. This is tedious work, but effective.

  2. If you have a tumbler, you can use steel shot to burnish the piece. It will become work-hardened just after a few minutes. (Don’t recommend tumbling with stone in place.)

  3. Annealing the silver (without the stone in place) is fairly easy. Heat the piece evenly to 900c (dull pink) using a larger torch tip, then immediately quench it in water, then pickle to remove the scale.

Sterling tends to soften after applying solder, if it is allowed to air-cool. Immediately quenching it afterwards helps, but that becomes a longer process having to pickle between each solder step.

Cheers!

-Troy

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Can you hammer-harden it? heat hardening is not that often done with silver, and generally takes 1300 degrees or more, plus quenching and multiple steps-- and an oven won’t do it. Hammering would make more sense if it’s possible.

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I have to agree with troy. repeated heating and quenching will risk fracture of the stone by thermal shock. If the stone is unheated treated, you are taking a risk even though you are using a low temperature, in changing the stone. cpearson also makes a point the tempering temp of sterling is higher- 1300F or more… a dull red… Your best bet to protect a valuable to protect a valuable stone is to remove it, despite the added hassle. Better safe than sorry. Work hardening either by hammering or burnishing can be done but if the wire is thin, hammering will flatten the wire out. Burnish is tedious especially if there’s a lot to burnish… it would be easier to remove the stone and reset it.

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Thank you, very helpful. I think I’m going to do the heat treat option and just bite the bullet and remove the stone.

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Thanks, I will take your advice (and that if the other commenters). I appreciate it.

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That is an option when I remove the stone. To be sure, if i use a torch for the initial application of heat, and then long periods at 600 degrees or so (60 mins, roughly), is that effective, or is the oven simply not hot enough to matter?

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My understanding is that you have to take it to 1300-1350 F first, then quench, cool, and bring to 600. So definitely not an oven thing.

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Hi Paul,

I just realized I called out 900 Celsius versus 900 Fahrenheit for the temp unit… Sterling melts at 893C / 1640F. Apologize for that!

I have not been very successful with the dull red temps as @cpearson1960 and @StevenH26783 mentioned. Which is definitely in the range of annealing and probably better for delicate wire work. I’ve been relatively successful using ~900-1000F, dull pinkish red, but what works for me is definitely a personal preference.

For the tempering step, a standard oven may reach 600F, but our oven (and the Mrs… will not let me test it :slight_smile: …) only goes up to 550F on the dial.

A toaster oven might be an option, never tried though.

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I don’t think that a toaster oven will get that hot either. I generally don’t heat harden my work. I probably will need a kiln with good temperature control. If are going to do filigree and fine wire work it might be worth investing in. Look kilns up at RioGrande. You could pose the question also to the Ganoksin/Orchid website… several of us are both this and the Orchid website. If you aren’t on Ganoksin/Orchid, it’s worth it if you are a jeweler, either just home hobbyist or professional.

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Many silver alloys can be heat hardened, which means the metal becomes harder as its thickness is reduced. Here are some steps for heat hardening silver:

  1. Anneal: Heat to 1200°F (760°C) for 30 minutes for assembled pieces and 1370°F (743°C) for non-assembled pieces.
  2. Quench: Quench in water or pickle solution.
  3. Heat: Heat to 650°F (343°C) for 30 minutes.
  4. Air cool: Allow to air cool.

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Stuller

Articles: How To: Annealing Gold, Silver, and Platinum - Stuller

Nov 16, 2023 — The more you reduce the thickness, the harder the metal gets. … Many silver alloys can be heat hardened. Process to heat harden, anneal for 30 minutes at 1200°F (760°C) for assembled pieces and 1370°F (743°C) for non-assembled pieces followed by rapid water quenching. To harden, heat to 650°F (343°C) for 30 minutes, quench or air cool. For Continuum sterling silver, use a higher temperature of 800°F (427°C) for 30 minutes to harden. Fine and sterling silver will work-harden when rolled, drawn, or forged. … Most of the platinum alloys cannot be appreciably heat hardened. Platinum alloys will work-harden when rolled, drawn, or forged.

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United Precious Metal Refining, Inc.

Helpful Hints for Sterling Silver - United Precious Metal Refining, Inc.

Dec 2, 2020 — Sterling silver may be hardened by the following methods: For hard rolled sheet, plate and wire, solution anneal at 1200 degrees F. for 20 minutes and quench in water or pickle solution. The articles are then placed in a pre-heated oven at 300 degrees C / 575 degrees F. for 1 hour and allow to air cool.

You can also try these methods for hardening sterling silver:

  • Hard rolled sheet, plate, and wire

Solution anneal at 1200°F for 20 minutes, then place in a pre-heated oven at 575°F for 1 hour and allow to air cool.

  • Argentium silver

Heat in an oven or kiln to 580°F for 45–60 minutes, or at 365°F for approximately two hours. Air-cool to room temperature.

You can also harden sterling silver by rolling, drawing, or forging fine and sterling silver.

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PS: if you are going to use a torch, “blue temper” is 575F… this works best for tempering small homemade steel tools such as punches out of tool or carbon steel. Dark gray is 800F. The steel has to be shiny clean. You can experiment with shiny clean wire and small pieces of clean silver sheet to see temper colors starting with straw at 390F through purple to dark purlple at 520 -540F… These temper colors are approximate and show some slight variations from different tables. Also note that temper colors are transient… continued torch play will overshoot, backing off the flame will undershoot… small steel tools can be tempered easily as steel can be quenched. I don’t think it would be possible to use a hand held torch to apply the exact temperatue for any systained period of time…
A discussion can be found on the ganoksin/orchid webside by googling “tempering silver”… Prolonged overheating of silver will cause it to crystallize and cause it to become crumbly… learned that accidentally and ruined a piece I assume that you are working with sterling. Fine silver temps a slightly different… the bottom line is that even with a kiln, heat hardening of sterling silver does not work very well.

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Super duper helpful. Thank you!

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are you tracing amber trade routes also? How is the turquoise project going? Have you made any more headway?

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Yes and sort of. For millennia, various long-distant routes interconnected, so it’s part of the story. My focus has been more on the Indian Ocean and Red Sea, but there are many “hub” points that changed over time, and a lot of… well, how do I say this, “effort” went into controlling various segments, as it could make an empire incomparably rich (through taxation and duties, both ways).

I had to draw a line in the sand and stop the research to pivot to documenting. It’s such a deep, and to me, cool subject that I feel I could just keep going. So hopefully i can get a draft out for review in the next month or so.

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Once reviewed and cleaned up will you be publishing? Would be very interested in reading your work.