The Studio – Jewelry Blog by Rio Grande

Metal Hardness: It Ain’t So Hard

Feb 7, 2013
10 Comments

Knowing how to choose the correct hardness of sheet and wire metals for your jewelry techniques and designs helps you achieve the good-looking, long-lasting results you want. Below, we share some of what we know about metal hardness and we hope it enriches your experience at the bench.

Metal hardness is one of the trickiest things to try to explain—the term is relative to the particular metal or alloy, for starters; depending on the elements that make up each particular alloy, what's called "hard" in one metal won’t bend, form, work, or feel the same as a material designated as "hard" in another metal.

The Hardness Relativity

Metal is composed of individual crystals arranged in a pattern and density specific to that type of metal. Because of this, the range of hardness from soft to hard will be relative to each metal (see the Vickers hardness chart below). Dead-soft sterling, for example, does not feel or behave the same as dead-soft white gold.

If you will be soldering on the piece you're making, you may as well start with dead soft because it's easy to work with and any hardness the metal may have will be lost when you apply heat to solder. If you will be cold-working the metal (manipulating, forging, twisting, folding, etc.), you may want to start with dead-soft metal and anneal it every so often as needed to resolve the work-hardening and return the metal to a dead-soft state. Jewelers who wire-wrap usually use 1/2-hard wire because it holds its form well in the finished design—as the wire is bent to wrap it, the working hardens the wire further so that the finished jewelry is stronger.

Any kind of cold working such as rolling, drawing, bending—even uncoiling and coiling wire—increases the hardness incrementally. Annealing can return the metal to dead soft, and further work will again begin to harden it. Mills that make sheet and wire typically measure the hardness of their products based on how much the product has been worked (a percentage of reduction, for example, in rolled sheet or drawn wire) since they were last annealed to dead soft.

The descriptions below offer, in general, what you can expect from the various hardnesses, but remember that these will vary in degree depending on the metal you’re working with, what you’re making and how you work.

Dead Soft

Metal that is dead soft is in a relaxed state at its molecular level, so it is easy to bend, shape and hammer. The act of bending or shaping will gradually work-harden the metal—right up to the breaking point. Dead soft metal will not hold its shape if put under stress in structures such as hinges or clasps.

1/2-Hard

Metal that is 1/2-hard has been worked a bit, tightening the grain at the molecular level. This metal is harder to bend and hammer, but it is still possible in some cases to shape the metal—it just takes more force. While still malleable, it will also hold its shape under a certain amount of stress; it is ideal for wire wrapped structures that will support other components. If you are fabricating an item that needs both strength and a thinner gauge, you would probably choose 1/2-hard.

Full-Hard

Metal that is tempered (or significantly work-hardened) will be difficult to bend but will hold whatever bend you put into it pretty stubbornly. This hardness is ideal for clasps or hinges.

Spring-Hard

Metal thoroughly hardened will lose pretty much all of its malleability and will actually spring back into its original shape when bent by hand. This hardness is ideal for ear wires, jump rings head pins and pin components.

It is important to remember that metal hardness is changeable. Metal alloys will harden and soften in a number of ways. Most metal alloys used to make jewelry become harder from cold-working (stressing) them and can be made softer by a process called annealing.

Work-hardening can be pictured easily if you imagine bending a paper clip. Keep bending the paper clip back and forth, and eventually it breaks. With each bend the wire has become "work hardened" and more difficult to bend until it simply can’t bend anymore and breaks instead. The same thing happens to sheet metal passing through a rolling mill or to wire pulled through a draw plate—each pass makes the metal a bit harder. Twisting wire will work-harden it, too; this is great to know for making ear posts—by adding a twist, you can keep the wire round while giving it more strength. When hammered into shape on a steel plate, sheet and wire become work-hardened (and they take on a nice hammered texture, too). Basically, anything done to the metal (without heat or abrasives) that changes the shape of the metal—such as bending, forming, twisting, stretching and so on—work-hardens it.

The point here is, if you start with dead soft metal and work it or stress it, it will get harder. If you heat and cool alloyed metal in a very specific process, you can harden it. On the other hand, if you take a harder metal and heat it either by soldering on it or by deliberately annealing it, you can soften the metal—all the way back to dead soft, if that’s what you want.

So What Hardness Should I Use?

For our customers, we tend to start by asking questions that can help narrow the options—starting with "How do you want to use your metal?" and "What metal are you using?"

If you will NOT be wire-wrapping:

  • Will you be applying any heat to your metal?
  • Do you plan to acid-etch the metal?
  • What type of jewelry are you making?

If you will NOT apply heat to the metal, we tend to recommend a dead-soft hardness and let the work harden the material in the finished piece. For items such as cuff bracelets, we tend to recommend 1/2-hard because they will further work harden, and you want the finished piece to be stronger than, for example, a pair of earrings. If you WILL be applying heat, start with dead soft because the heat will remove any hardness anyway. You can harden the finished piece as needed (see heat-hardening link below). If you plan to acid-etch the metal, we tend to recommend 1/2-hard or spring-hard varieties.

If you WILL be wire-wrapping, we tend to recommend:

  • For sterling or Argentium silver, use 1/2-hard. (Argentium tends to work-harden more readily than traditional sterling, so you may want to try a dead soft in that metal to see how it suits your work.)
  • For 14K white gold, use dead-soft.
  • For yellow gold, use 1/2-hard for 19–22 gauge; use dead-soft for 18 gauge and heavier.
  • For base metals, dead soft is the starting point for just about everything and can be work-hardened if needed.

If your finished silver or gold pieces will take some stress when worn (rings or bracelets, for example), you can harden the finished piece by heating it to increase its hardness. See our handy how to heat-harden silver tip for more information about this.

We hope this helps unravel the mysteries of metal hardness. At least it may be a good start. Nothing teaches better than experience, so I encourage you to experiment with hardness. Push the envelope and try different things with different hardnesses. See what works best for the work you’re doing and pieces you’re creating. And let us know what you discover—we love learning from your experience, too!

Eddie Bell
Mark Nelson

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Comments (10)
  1. I understand all the above pretty well. I do have one question though; short of buying hard sterling wire, how do I get my ear wires to firm up without distorting them? I’ve hammered them but they ever seem to get as rigid as I’d like and are usually easily deformed. Any hints for toughing up my ear wires?

  2. Eddie you have the ability to take technical information to a level that is more interesting and useable. Nicely done. I will be referring to this frequently.

  3. What a GREAT ARTICLE! So concise. I spend a lot of time talking with students about temper — now I can just send them to the blog!

  4. We’re so happy to know that you found this information helpful and that it can be a resource for your students. Thanks so much for reading and taking the time to share your feedback!

    –Molly

  5. Wendyoes — You need to tumble them. Have a look at item 202209. It is an economical way to harden your ear wires, jump rings, etc. This was my favorite purchase from Rio last year. It is also a great way to put a quick polish on components or finished pieces. This is a kit that comes with everything you need except silicon lube, which will ensure a perfect seal when closing the tumbler.

  6. I too ruined a pair of earings that I built fine silver wire into PMC3 earings. The wire was flimsy so I carefully used hammer to work harden with disastrous results. Of course all of this was post firing and I couldn’t replace the ear wires. Still working on fixing this.

  7. Hardening sterling silver ear wires.
    It takes quite a bit of work to make a significant difference in the stiffness of sterling silver wire. For example, if start with soft wire and you get a 20% reduction by drawing the wire through a drawplate, that will result in about 25% increase in tensile strength and that would then be considered ¼ hard. Just hammering lightly on the wire will give it a kind of “case” hardening but the core of the wire will remain soft because it wasn’t deformed. This is what happens when an ear wire is put in a tumbler, as was suggested in one of the posts. In fact we use that technique using a magnetic pin finisher to add a little hardness to some products. You can notice the difference after working it in this way. However, that isn’t the same as starting with a hard piece of wire. If you don’t want to buy half hard wire to make ear wires you can make your own if you have a drawplate and draw tongs. A 38% reduction will render the wire to ½ hard, which is about right as a starting point for an ear wire.
    Eddie

  8. Fine silver ear wires
    I don’t know of any way to make fine silver stiff enough to make a good ear wire. The reason silver and gold are alloyed with other elements is to make the resulting alloy stronger. So you might wonder how adding soft copper to soft silver can make the silver alloy harder. Metals have a crystal structure in their solid state but since atoms are too small to see, I’ll enlarge them to marble size. If you can visualize a shallow box and the bottom is completely covered with marbles of the same size. Tip the box up so all the marbles are tightly packed. The horizontal rows will stagger, i.e. marbles in one row fall into the gap between the two below it. If you draw the pattern out on paper you could see marbles lined up in crossing diagonal rows in addition to straight horizontal lines but the vertical row would be interrupted by the offset of half a marble every other row. The point is, this is what a metallic crystal plane looks like and you could pick out straight parallel rows. A metallurgist would say the rows are in a lattice. Because the marbles are all the same size the lattice lines are straight and parallel. Imagine that some of the marbles are randomly removed here and there and replaced in the exact same spot with smaller marbles. Tip the box so all the marbles crowd one another and again are tightly packed. Now you should see that the lattice lines are distorted here and there where the smaller marbles allow the marble above it to fall out of line. Silver atoms have a radius of 1.75 angstroms (Å), gold atoms are nearly the same size at 1.79 Å, but a copper atom is somewhat smaller 1.57 Å. The effect of lattice distortion is an alloy with greater strength and hardening and metallurgist call this solid solution strengthening. So why did you mention the gold atom radius, grasshopper asked. Well, it was to point out what may be obvious to you by now. That is adding soft gold to soft silver doesn’t produce a harder alloy because the atoms are about the same size and there is little lattice distortion. However, adding copper to gold does make a harder alloy for the same reason that it improves the strength of sterling silver. Fine silver has not lattice distortion so it will always be softer than sterling.
    Eddie

  9. That makes a lot of sense. I wonder how many instructors have this knowledge. I guess it’s one of the problems in using the ear wire as a design function. I have to remove the copper from sterling silver to add to PMC. I thought I was saving myself a step not having to deplete the sterling silver by using fine silver. I’m going to try to tumble earings and see what happerns (pair #2). I wish I had this article prior to making 2 pairs of earings. Very helpful information Eddie. Thank you for your time and knowledge. PS: I’ll post pics when I’m finished.

  10. I sure hope this doesn’t sound ignorant…and, I am a student. :) I read your instructions for Heat Hardening things like bracelets & rings…however, WHAT do you do this in? A special Kiln? Would you mind giving some information on the equipment needed to do this? Thanks so much.


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