Gold Leaf Science: Why Gold Can Be Beaten Hundreds of Times Thinner Than a Hair
Gold can be beaten into leaf about 0.1 micrometers thick, hundreds of times thinner than a human hair, because it is the most malleable metal known. Its atoms sit in a face centered cubic crystal that lets layers slide past each other instead of cracking. For readers in Los Angeles who love both science and fine jewelry, this is the same property that lets a goldsmith shape, texture and set a ring by hand.
How thin is gold leaf, really?
Gold leaf is usually around 0.1 micrometers thick, according to Wikipedia's entry on gold leaf, which draws on The Physics Factbook. The Physics Factbook collects several sources and gives a range of about 0.1 to 0.125 micrometers, or four to five millionths of an inch. Wikipedia's article on gold states that a single gram of gold can be beaten into a sheet of about 1 square meter, and an ounce into about 28 square meters.
At that thickness, gold stops behaving like the solid metal you know. Wikipedia notes that gold leaf can become semi transparent, and that light transmitted through it appears greenish blue, because gold strongly reflects yellow and red light. Hold a sheet up to a window and the warm gold you expect turns into a cool green glow. The color of gold is not only a surface; it is the way the metal treats each wavelength of light.
Why is gold so malleable?
Malleability is the ability of a material to deform under pressure without breaking. Gold leads every other metal here, and the reason lies in its structure and its bonding.
- A face centered cubic crystal. Gold atoms pack in a face centered cubic lattice. This arrangement has many close packed planes, which give layers of atoms many directions in which to slip.
- Metallic bonding. In a metal, outer electrons are shared across the whole crystal. When a layer of atoms slides, the bonds do not snap the way they do in a brittle ionic crystal like salt; the electron "glue" simply follows.
- Dislocations. Real crystals contain line defects called dislocations. When you hammer gold, these defects move through the lattice, letting the metal flow a little with every blow.
- No oxide skin. Gold is chemically noble and does not form an oxide layer in air, so a goldbeater can keep working the surface without it turning brittle or flaky.
Wikipedia's gold article also notes that gold can be drawn into a wire a single atom wide and stretched considerably before it breaks. Few materials tolerate that kind of treatment.
Goldbeating: a craft thousands of years old
People understood gold's malleability long before anyone could describe a crystal lattice. According to Wikipedia's entry on gold leaf, Egyptian artisans were beating gold into leaf about five thousand years ago, pounding it with a round stone, and gold leaf work is known from Anatolia, in present day Turkey, as early as about eight thousand years ago.
The traditional process is a lesson in patience. A gold bar is rolled to about 25 micrometers, cut into squares and interleaved between layers. In the early trade those layers were goldbeater's skin, a membrane made from ox intestine; today materials such as Mylar are used. The packet is hammered, the leaves are cut and restacked, and hammered again, until the finished leaf is about 100 nanometers thick. Most goldbeaters make 23 karat leaf, according to the same source.
From gold leaf to a ring: the same property at work
Jewelry is not made of gold leaf, but every handmade piece depends on the same malleability. Pure gold is too soft for daily wear, which is why fine jewelry uses 14K or 18K alloys: a little copper, silver or other metals make the crystal harder while keeping it workable. Our guide to the chemistry of yellow, rose and white gold explains how those alloys change color and strength.
Texture is where malleability becomes visible. The Celestial Raw Ring is 18K solid gold with an organic raw texture and earth mined conflict free diamonds scattered like stars. The surface keeps a record of how the metal was shaped, the way a beaten leaf keeps the memory of each hammer blow.
When a diamond is set, malleability matters again. A goldsmith pushes metal over the edge of the stone to hold it, relying on gold to move without cracking.
The Wavy Diamond Heart Bangle uses 17 g of 18K gold shaped into a wave, with ethically sourced natural diamonds totaling 1.05 ct and a central heart diamond of approximately 0.65 ct. A curve like that is only possible because gold agrees to bend.
Why this matters when you buy gold jewelry
- Karat is a trade off. Higher karat means richer color and softer metal; lower karat means a slightly harder surface.
- Texture hides wear. Raw and textured finishes show fewer fine scratches than high polish.
- Gold can be reshaped. Because it is malleable, solid gold can often be resized or repaired, and it can be recycled, which plated jewelry cannot offer.
Margaret Krinetz Fine Jewelry, handmade in Tel Aviv and shipped to Los Angeles, works with this property every day. Margaret, who has a background in physics and biology, still finds it remarkable that the same atoms that turn green in a thin leaf can hold a diamond for a lifetime. For the cosmic side of the story, read where gold comes from.
Frequently asked questions
Is gold leaf real gold?
Traditional gold leaf is real gold, most often 23 karat, beaten to roughly 0.1 micrometers. Imitation leaf made from other metals also exists, so check the label.
Why does thin gold look green when light shines through it?
Gold strongly reflects yellow and red light, so the light that makes it through a very thin sheet looks greenish blue.
How long does delivery to Los Angeles take?
Every piece is handmade to order in 4 to 6 weeks, then shipped by DHL Express to Los Angeles in about 3 to 5 business days, with free shipping on orders over $1,500.
Curious how a ring is shaped from metal that behaves like this? Explore the handmade gold rings or write to us through our contact page.
Sources: Wikipedia, "Gold leaf" and "Gold"; Jenifer M. Vilfranc, "Thickness of Gold Leaf," The Physics Factbook (ed. Glenn Elert).