Explaining the science of doorknobsfrom @fineasjackson

Transcript

So look at this old tarnished doorknob. It seems dull. It looks dirty. If you moved into an older house, your first instinct might be to polish it or rip it out entirely and replace it with a matte black or stainless steel handle. But that dark cloudy finish isn't dirt. It's proof that the handle has been protecting every hand that's ever touched it. This is Chasing Best episode 48 and today we're looking at the invisible engineering we erased from our homes. For decades, heavy unlacquered brass was the standard for doorknobs, push plates and handrails. We assume today that this was just a Victorian style choice. But our great grandparents weren't just decorating. They knew what this metal did. Brass is an alloy of copper and rank, and copper has a property called the oligodynamic effect. When bacteria or viruses land on unlacquered brass, copper releases ions that breaks them down. Within a few hours, they're dead. The surface essentially sterilizes itself between every hand that touches it. And this wasn't a secret. Before antibiotics, hospitals deliberately spec'd out high touch surfaces with brass. Think bed rails, door handles, instrument trays. But in the mid twentieth century, our tastes shifted. Stainless steel and aluminum came in. They were cheaper, better, and crucially, they stayed shiny. They looked clean. So best stripped the brass tier, replaced it with stainless steel and cheap painted metals. But the problem is that bacteria can survive on stainless steel for days, sometimes weeks. Every hand that touches that shiny handle picks up whatever the last hand left behind. The services that good the cleanest worse doing the best. And even worse, when people do buy brass handles today, they often get them lacquered. That means coated in a thin layer of plastic no that the handle itself doesn't tarnish. The problem is that plastic seals off the copper entirely. It stops the metal from doing anything at all. Now the next time you walk into an old house and see a dark cloudy brass handle that looks like it hasn't been cleaned in decades, don't polish it. That tarnish is the metal reacting with the oil and microbes on every hand that's turned it.