Gold cohesion experiment (ultra-high vacuum, 1950s)

The foundational experimental proof that primary chemical bonds have million-psi strength when surface contamination and roughness are eliminated. Used to set up the two-axis framework (contamination, roughness) for the rest of the module.

If you keep something clean and bring it together without any oils or absorbed gases or anything else on the surface, and you actually have two primary bonds coming together, they will bond with tremendous strength. They did this in ultra-high vacuum systems with gold back in the 1950s. They would take two very flat surfaces of gold and bring them together in an ultra-high vacuum after they made them very clean, and they would stick together with the strength of a braze joint. They would still fail at the braze joint, and that's because — well, does anyone know why? What's the second inhibitor to bonding? It's not just chemical contamination on the surface. It's surface roughness.