Etruscan gold bead diffusion bonding

Cited as evidence that soldering predates the modern process by thousands of years; the joint was effectively a transient liquid phase diffusion bond.

Soldering and brazing are the exact same process. One occurs at high temperatures, one at low temperatures. How did we get to two different sets of terms? Soldering came first. Soldering has been done for thousands of years. I showed you the little solder beads on the Etruscan earrings and King Tut's dagger, where they were soldering with tin. Tin has a melting point below 450° C — it's 212° C — so it's soldering. They actually ended up forming a transient liquid phase diffusion solder joint. Soldering has been around for years; brazing came a little later and people gave it a different name.

Etruscan gold earrings used tin between copper-base and gold beads to make TLP diffusion bonds, ~600 BC. Sectioned jewelry shows tin gradient by microprobe. Tom's rhetorical move: "the Etruscans didn't file an infringement" against the Pratt & Whitney patent.

For example, the Etruscans — I think I told you this before — this is a gold earring made by the Etruscans around 600 BC. They used this technique to put these little gold beads on what is a copper or brass substrate. You can kind of see the color of the gold beads. Here's a bad joint — see the defect — obviously they threw this earring out. People have actually sectioned some of this Etruscan jewelry and shown that they used tin with copper and gold to make a transient liquid phase diffusion bond. So in fact you could argue that the Pratt & Whitney patent could have been invalidated, but the Etruscans didn't file an infringement.

Etruscans used tin to bond gold beads to copper objects ca. 600 BC by furnace heating, producing diffusion bonds. Tom's recurring joke: Pratt & Whitney patented the process in 1972 only because the Etruscans didn't file an infringement.

Welding is often applied as an art. As soon as someone gets a new heat source, they often try to use it to weld. People discovered over the ages how to do soldering and brazing on art objects. They even learned to do diffusion bonding. When we get to diffusion bonding, I'll tell you the story about how the Etruscans used to use tin to bond gold beads to copper objects. They just put them in a furnace and ended up getting a type of diffusion bond. I always say Pratt & Whitney patented this process in 1972 only because the Etruscans, who used it in 600 BC, didn't file an infringement against them. Some people think that King Tut's dagger had the same type of gold beads attached to it by this type of diffusion bonding. No one knows because no one's willing to cut up the dagger to find out.