The one thing everyone gets wrong about cleaning ancient coins

I see people scrubbing their new finds with soap and water all the time on here. That ruins the patina and can actually damage the surface details. I learned this the hard way after ruining a nice Roman bronze from a dig in York last summer. Just use distilled water and a soft brush if you really need to clean it, and even then go slow. Has anyone else accidentally stripped the patina off a good coin?

3 comments

3 Comments

drew_hart41mo ago

Distilled water still strips patina if you scrub too hard. I've been cleaning coins for about 8 years now and a lot of that patina you think is damage is actually the original surface. Some of my best looking bronzes came out looking dull and flat because I was too careful with water. The real trick is leaving them alone unless there's active bronze disease. If the dirt is stable, just let it be. I have a Trajan sestertius that looks horrible but the patina is completely intact and that's worth more than a shiny one.

ivan7741mo ago

Keep a soft toothbrush and distilled water handy but only use it if you see white powdery spots. If the dirt isn't moving or flaking, walk away from it.

the_piper1mo ago

Oh wait, that's a really good point about patina being the original surface! I've been collecting Roman coins for a few years now and I see people on eBay paying way more for dug up crusty bronzes than the cleaned ones. So here's my question - how do you tell the difference between stable patina that's actually protecting the coin versus active bronze disease that's gonna eat through it? Like is there a test or something? I've got a Constantius II coin where the surface has this weird greenish crust but it hasn't changed in over a year, so I'm scared to touch it but also worried it might be slowly rotting.