Masterclass: How to polish aluminium parts, with CycloRetro
Welcome to Masterclass, the latest new series on CyclingTips. In it, we’ll take you behind the scenes with renowned artisans to share the tips and tricks which help make them masters of their craft. In some cases they’ll be skills you can practise at home, other times they’ll simply provide an advanced understanding of how something is created.
In this first addition, we look at how to mirror polish new or used aluminium with Chris Howard of CycloRetro.
Polished, chromed, and silver components are coming back. Whether it’s the boom in rebirthing vintage rides to their former glory for events like L’Eroica, or through those building a brand new bike with a classic aesthetic, the love of shine is making a resurgence.
Chris Howard runs CycloRetro, a small home-based business based in Melbourne that is focused on bicycle restoration, pantographing, polishing, and replicating designs of years past. Over the last few years, Howard, a trained graphic designer and former bike painter, has earned himself a reputation as being an artisanal master in his restoration craft.
Wanting to know more about how he goes about turning well-loved and dull bike components into mirror-polished masterpieces, I visited his workshop and bothered him with a bunch of questions. They were questions he was more than happy to answer because, as it turns out, polishing parts takes a long time (warning: it’s a tedious task), and Howard would happily spend that time elsewhere in his restoration business.
Before we start, it’s worth knowing what can and can’t be polished. For Howard, he mainly works with aluminium and steel components. Carbon components are obviously off the table, as are plastic. This can make polishing new high-end components rather limited.
“Looking at new Campagnolo, it’s pretty much Potenza or Athena [ed. which is discontinued],” says Howard. “You can get really tricky, such as swapping Super Record shifter/brake blades and paddles out for Athena metal versions, so you can end up with Super Record guts, but in a silver finish. Likewise, I’ve turned silver Potenza cranks to make it look like Super Record.”
Looking through Howard’s workshop (away from the polishing area mostly pictured), there are stacks of boxes containing new Campagnolo Potenza components, and a number of plastic tubs filled with older and highly sought-after Campagnolo components. “I don’t often take new old stock (NOS). Usually, people send me well-abused stuff, stuff that I can then restore,” he says. “I like to resurrect old stuff, rather than destroy NOS. But dealing with newer Potenza stuff, you have no choice.”
Amongst the stacks of Campagnolo, I didn’t find much Shimano at all, something that Howard admits he only sees 10% of the time.
“For Shimano, any metal components can be done, but the aesthetics may not lend itself all that well to the polished look,” Howard says. “Dura-Ace 7700 is what I do most of in Shimano, also 7400 stuff.”
Howard’s claim of not seeing much Shimano may undersell his experience with it, and he later suggested that he’d done approximately 40 7700 groupsets over the years. More recently, he’s also dabbled with a few 7800 groupsets, sometimes pantographing older logos on to the surface.
Speaking of Potenza, Howard suggests that starting with the silver groupset makes the work much easier. It means you can be a little less anal about polishing every single nook and cranny. But unfortunately, as Howard has found, Potenza in black is readily available and the silver option is forever in short supply. Sometimes he’ll avoid the six-month wait and choose to polish the black components. It’s certainly more work, but sometimes you have to work with what you’ve got.
Just as any chef will tell you, most of the time investment is in the prep work, and it’s no different in Howard’s craft. Howard will disassemble the selected parts as much as needed. With newer Potenza, he chooses to keep many of the factory riveted pieces together, choosing instead to work with the complete sub-assemblies.
Older Campagnolo components are easier to disassemble, providing more ready access into the tight spots and with less risk of damaging delicate parts. Keeping a careful check on every single separate part is critical, especially little washers and other tiny bits that are essentially irreplaceable.
“You can go nuts and remove all the parts, but you should just take off what you have to. I leave the springs in, ’cause I work around it,” Howard says. “Campagnolo are going to assemble these much better than I can, so if I don’t have to pull it apart, you’re better off not to.”
Stripping, anodising, coating, and painting
Once all the parts are in pieces, Howard will work on removing whatever logos and coatings are in place. It can be very tricky to know what coating each component uses, and as Howard has found out, there’s very little consistency, even within the same groupset. Using the Potenza examples, Howard showed amazing efficiency in making the stock logos disappear.
“The first process is to remove the logos. Most come off easily,” Howard says. “Steel wool for the brake calipers. Paint stripper to remove the screen printing, such as that found on the rear derailleur. The brake levers are extremely stubborn. You have to sand off the logo on the brake levers.”
With the logos removed, it’s time to strip the anodising away.
“Easy-Off Oven Cleaner is the easiest way to get anodising off,” Howard explains. “I go through this stuff like you wouldn’t believe. It’s very cheap. I can use a tiny amount at a time without the chemical going off. And it’s readily available. It’s very effective at getting the anodising off.
“Cover it well, do it in a nice ventilated area, and don’t breathe it in. It usually takes a few minutes. Brake calipers and levers are generally more stubborn and require a second coating, whereas the cranks and derailleurs, the anodising comes off really quick. For Potenza, if the part is still shiny, it still has anodising on it. You want it more evenly dulled. Sometimes it can take five minutes, sometimes it can take five hours [with the oven cleaner].”
Howard explained that Shimano’s older Dura-Ace stuff is clear coated, not anodised. So you’ll need to use paint stripper on it before starting any polishing.
“After the oven cleaner, you want to clean everything off [with water]. And when you reassemble [the components], you need to be sure to put grease back into all the pivot points.”
Buffing to bare metal
Once the chemicals have done their thing, it’s time to get buffing. In buffing, you’re effectively taking microns of metal away to achieve a smooth and consistent finish. “If you’re working with older groupsets, that have dings and scratches all over them with use, then a coarse cutting compound and a coarse cutting wheel will do the job,” Howard explains. “You’re effectively restoring the alloy back to what it used to be like at the factory; you’re getting it back to the nice, smooth finish. From there, you can engrave, and then highly polish the component.”
However, it’s not just old parts that need such treatment.
“The frosting (of Campagnolo Potenza, as pictured above) can be hard to get off. Some of the anodising, such as on the levers, will leave indents in the metal once you’ve stripped it off,” Howard says. “From there, you still need to buff it out of the metal, effectively cutting the metal down past that point.”
Tools of the trade typically include a buffing wheel mounted on a bench grinder. However, it is possible to achieve similar results with a small rotary tool (such as a Dremel) or purely by hand with progressively finer grades of sandpaper and steel wool.
“A standard bench grinder will do the job, but I prefer something with a little more horsepower than the cheapest units. Doing so allows you to use a bigger wheel.”
For those sticking with sandpaper, start with dry, then move to wet/dry paper, then to fine grits, such as an 800-grit wet and dry.
If you do decide to go the bench grinder route, then Howard suggests using a high-grade cutting compound, with a cutting compound wheel. The cutting compound is effectively a wax-based product that has some fine grit in it. The embedded abrasives help cut away at the surface, and the wheel merely acts as a way to hold and apply the compound.
“You usually get it with polishing kits,” Howard says. “I use the Josco brand. There’s a whole heap of other ones out there.”
“Things can get really hot when you buff parts (on a wheel),” he continues, while wearing some thick leather workshop gloves. “Sometimes it’s best to juggle between multiple parts so they don’t get too hot. Likewise, you need to be careful where any rubber or plastics are involved, such as on the rear derailleur. If you can get it too hot around here, it can be the end of that derailleur.”
“It is a learning process,” Howard explains. “If you’re working with older, damaged parts, where there’s road rash or a gouge, then you have to work the aluminium in the same way [of the gouge]. The aluminium is effectively made up of pores, and when you get a scratch, you need to understand the structure of the metal. You can’t just polish them out from one direction; you need to constantly change direction to evenly polish the grain.
“Diagonally, up and back, side to side. it’s like sanding warped floor boards: you need to do it evenly and until you get that flat finish. You need to get rid of all the against-the-grain scratches and achieve a flat finish before you can polish it with the grain. Some people actually like that brushed looked, but if you want it shiny, you need to polish it with the grain. If you’re using new components, such as Potenza, it’s easier to do and you’ll get a good finish because it’s brand new.
“On a part that’s quite wide, such as a Potenza crank, you want to make sure that you’re even with your direction and not go off on an angle. Otherwise, you’ll see lines in different directions.”
It’s at this stage of the process that Howard takes the parts into his workshop and does any detailed pantograph or engraving work required. Once that is ticked off, it’s back to the buffing wheel to get the mirrored shine.
Can I see myself yet?
Remember when I said polishing metal is all about the prep? Well, if everything has been done right, the prep is now over and the end is near. In this final step, the goal is to achieve a perfect mirror finish.
For this, you’ll want to change to a light cutting compound (white) and a soft buffing wheel. If you’ve decided to spend hours and do it by hand (and endured the sore fingers), then a metal polish and a clean rag will be the tool of choice.
Similar to the previous stage, the goal is to get a mirror-like finish, but this time, polish it with the grain of the metal. In the example of the Potenza crank, Howard recommends working “straight down on the face of the crank. A nice even finish here is important or otherwise you’ll see it in the sun. But it’s not so noticeable on smaller little parts.”
The end result
In the end, if done right, you’ll be left with a part that makes others stop and take notice. You can clear coat your handiwork, or just occasionally go back to that last polishing stage when required.
As one would expect, Howard says that this type of labour-intensive work can be slow going.
“I’d only get a set of levers and one set of brakes done in an entire day of work,” he says. “That’s from starting with a part straight out of its original box, to being able to put it back in the box as a completed product (including pantograph work).”
Pricing wise, for CycloRetro to customise and polish a set of Potenza levers, it would typically cost about AU$180. Both brake calipers would be AU$150, and a crank is AU$150. All up, customers could expect to pay AU$600-$700 in labour to have a groupset stripped, polished, and pantographed. And if you follow Howard’s requests, pantograph work would cost less.
“I’d love it if people did their own polishing and sent it to me pre-polished”.