Here is a quick video of our anticlastic cuff bracelet. Note how the cuff is only flexible in one direction: read on to find out why!
The short answer is: well, it depends on how you work your gold whether or not it will come out soft and flexible, or hard and springy (like ours).
By hammering gold while it is cold, you cause the very atoms of the element to rearrange themselves and to lock together. This increases the tensile strength of the gold, allowing it to have better "memory." Memory is when a piece of gold remembers what shape it was hammered into. In our case, it would mean that the gold remembers the shape of the bracelet or earring it was formed into, and so it springs back into shape after you twist it to put it on your wrist or ear.
So you don't heat your gold at all when you work with it? Again, yes and no. We heat the gold ingot once at the very beginning, which softens the gold and allows us to begin work on the item. This process, of heating and softening/relaxing, is called annealing. If you heat gold too much, or if you don't work harden the gold again after, the gold loses almost all of its memory and goes completely "soft." Gold that is totally soft is almost useless as jewelry because any little scratch, dent, or bend will show in the metal. Soft gold is also liable to easily bend (and not spring back) and then break at the bent point.
The final shape of the piece also lends to the strength and springy nature of the jewelry. Most of our bracelets start out in the same manner: after being slightly softened, Bill mills the ingots several times to produce a sheet of metal roughly the same thickness as the desired finished product. He then uses a press to get the basic shape formed. When Bill first began making bracelets, he would hammer a bracelet straight out the flat ingot. However, the amount of hammering and work hardening that went into hand hammering the gold frequently over worked the gold, causing there to be so much stress and tension between the gold atoms that the gold would snap in half. The use of the press puts much less stress on the gold from the very beginning, allowing us to actually work and shape the gold more (before it reaches the breaking point from tension)
There are two main styles of hammering that Bill works in: synclastic and anticlastic:
|Synclastic Hoop Earrings|
- Synclastic means that all the curves of a piece curve in the same direction. Think of the earth: latitude and longitude. While longitude wraps vertically around the globe, and latitude wraps horizontally, they both curve inward in the same direction. This type of forming allows a piece to bend/spring in on that shared curve.
- An anticlastic curve is one where the radial and axial curves do not curve in the same direction. Think of a Pringles chip. The horizontal curve bends upward, while the vertical (lengthways) curve bends down. These two opposing curves pull on each other, creating strength and flexibility in an outward manner.
To achieve these curves is simply another process of work hardening and hammering. As Bill so wonderfully put it, being a goldsmith is wonderfully simple work. Just by hitting the gold with a hammer, the gold spreads out and rearranges itself, forming natural curves. That is, when the gold is hit, the gold is spread out and away from the hit point. That spreading gold piles up in other areas, causing the gold to curve. It is simply by learning various metallurgical principles that allows you to harness this natural desire to curve that you can make springy bracelets!