How To Polish Bare Metal

The impetus for this post comes from the Medieval Arms and Armor exhibit at the Art Institute of Chicago. Specifically, this breastplate:

It's a cool looking piece of hardware, but what bugs me about it is the polishing detail. It's all scratched up! Imagine if your mechanic did that to the finish of your bike! Some poor peasant got a whipping for this, and a well-earned one too. Here's a closer look:

Yuck.



That armor is made from steel, and steel corrodes. Duh.

These days we use sand paper to wipe away blemishes, but they would have used an actual stone back then, or they'd drop the armor in a sand-filled barrel and roll it around the yard for a while. Either way, it gets pretty scratched up.

Bernhart Polyrer (c. 1425)

In modern times, again, we'd use progressively finer grit sandpaper to whittle away the scratches until they're polished so thinly that an observer can't see the difference anymore.

And that's exactly what I plan to do with this hub:

This old pista hub was once owned by the 1967 Illinois State Track Champion, and might have been one of the hubs she used to secure her victory.

As you can see, it has a factory-produced mirror finish that time and use have turned a little smudgy.

I will use a technique called "wet-sanding" to remove the mirror finish and replace it with a more even polished aluminum patina.

To do this yourself, you'll need:

• 600, 1000, 1500, and 2000 grit sandpaper

• A dab of water

• Patience

The goal is to strip the old finish with the gritty paper, then smooth it out with the finer stuff. 

I should say now, if it isn't obvious, that I'm writing this post during the off season. Which is to say, I have time and idle hands. 

Tips:

Rip small corners of sandpaper for easier use, and keep a clean towel on hand to wipe junk away. 

Create a "grain." That's the term for the direction of the scratches. You only want scratches to go one direction, which means all of your scrapes have to come from the same source. 

Wet the sandpaper in a bit of water, then start from one end of the hub and slide the sandpaper to the other end. Rotate the hub by 1/64th of a turn and slide from one end to the other, again. Repeat until you've gotten back to the first slide marks. Do this with the 600 grit paper first, then the 1000 grit, then the 1500 grit, and so on. 

It's important to keep your hand-pressure even too. Push down too hard and you'll make a gouge. 

You might find that once the factory finish is gone the metal looks wavy. This is because, well, it is. The formed metal in forged hubs like the one in this example doesn't settle evenly when pressed into shape, that's part of the reason the factory likes to apply a mirror finish, it fills in the small indentations to make the hub look smooth. To remove the waves, go over them with the 600 grit sandpaper and even pressure until they go away. This will take a while. 

After about six hours or more, this is what the hub should look like: 

As you can see, the hub catches and distributes more of the sun's light, and thus looks brighter than the mirror finish. 

This finish, however, is fragile. One stray strike of sandpaper against the grain can ruin an hour's worth of work. That's why I focus on the inside of the hub, specifically the "Campagnolo Record" label. The outside of the hub just got a quick treatment with a swatch of sandpaper wrapped around a power drill, but I still used the same method of increasing grit from 600 to 2000. 

The final task involves using a finishing product, like Mequiar's various treatments, followed by carnauba wax. Step one: use a scratch removal compound to prep the surface. Step two, use a polish to clean the surface. Step three, use the carnauba wax to seal the surface. Follow the product directions to get the best shine.

Quick note on Meguiar's products: I do not work for this company, nor do they give me and $ to support their product. However, I've detailed a lot of cars and bikes, and in my experience the Meguiar's stuff works best. If you want to save money, Turtle Wax is a decent runner-up at half the price. 

And just like that, you've wasted the whole day! Good job!