Vern Burke, SwiftWater Edge Tool Works
There’s a lot of debate in the antiques world about removing “patina” from metal objects. I’m going to talk a little bit here about patina and old tools.
The first thing to keep in mind is not to try to turn a nice vintage tool into a new one. Vintage handsaws, planes, and other woodworking tools can keep the signs of their use that give them character and still be put in condition to be perfectly usable. These goals aren’t mutually exclusive.
Let’s take, for example, handsaw cleaning. The first thing to come off any old neglected or abused handsaw is the surface rust. Rust is always bad, period, and should never be left on any tool you care about. It’s that simple. Get rid of the rust.
The next layer down after taking off the surface rust is usually a smooth, dark brown layer, mistakenly referred to as “patina”. Really, this is just yet another layer of rust. Handsaws may also have a layer of old pitch mixed in with the rust too.
A lot of people like to remove pitch from a handsaw by chemically softening it. In my opinion, this is likely to just make a mess. If the pitch is hardened, scraping it is usually the fastest way to remove it.
The last layer is the dark stains that rust leaves as a shadow when it’s gone. This is the signal to stop cleaning. Rust shadows don’t hurt the blade at all and any attempt to remove them will sacrifice steel from the blade, just the thing you don’t want to do to a nice vintage tool.
It’s also worth noting that rust and old pitch will impact the performance of the blade, since they add drag. A blade nicely cleaned down to just the rust shadows will be smooth and have little friction, making a better user saw.
Clean, but know when to say when.