Tips for Successful Metal Polishing
I’ve never been a particularly patient person, but I’m learning. And nothing helps teach patience like a project that demands patience. Take metal polishing. On the surface (pun intended) it seems like a simple proposition; clean the surface first, slap on some polish, work it in with a clean cloth and voilà, a perfectly polished and gleaming surface results. Unfortunately, when you’re working on old iron, it’s not always quite so simple.
On the bikes we regularly work on around here — mostly an odd assortment of 1970s to early 1980s Japanese and European road bikes — the major issues we see with metal surfaces are pitting and surface degradation from constant exposure to the elements, and — especially on mid-1970s Japanese bikes — hazing of polished engine cases with clear-coat finishes.
Surface degradation from exposure is a problem experienced by all bikes that see regular use. It can easily be kept at bay by simply cleaning your bike after every ride, or at least every other ride. A quick wipe-down of polished surfaces, followed by waxing, will add years to metal and painted surfaces, protecting them and staving off mild oxidation. It’s a best practice we know we’d do well to follow, but often don’t.
While getting a good sheen on our clear-coated engine cover — the subject of this issue’s How-To — we learned one very important lesson: Successful polishing takes lots and lots of elbow grease.
There are, unfortunately, no magic fixes. There is no one product that miraculously cleans and restores neglected surfaces, returning them to a brilliant luster with little more than a light rubbing. The hard truth is, once a surface has diminished significantly it takes work, and a fair amount of it, to restore that surface back to its original sheen.
Our clear-coated but faded engine cover (the clutch cover from editor Richard Backus’ 1983 Laverda RGS 1000) would only return its sheen after lots of labor. We tried other methods first, but hand sanding was the only thing that worked. Chemical strippers, which we figured would work great, were surprisingly ineffectual. We found that wet-sanding with 400-grit wet/dry sandpaper before moving to polishing compounds for a final polish worked best, and we should have gone to a final 600-grit for a really spectacular finish. A good polishing wheel was also critical, as was, well, patience.
It’s important to appreciate that there is no one way to clean and polish. There are things to avoid; harsh chemicals don’t seem to offer real advantages, and possibly place your health at risk. And there are protocols; start coarse and finish fine. For instance, on tough jobs, first wet-sand the surface with 400-grit, followed by 600-grit to remove any sanding marks. Follow up with a polishing wheel, starting with a brown compound, then a white compound, then a final finish with a hand polish. Over time, you’ll develop your own processes that work best for you.
After thoroughly cleaning our engine cover first, we tried stripping off the old clear-coat with a commercial paint stripper, figuring that should work well as clear-coats are usually a lacquer finish.
Unfortunately, that hardly put a dent in the clear-coat. It did, however, soften it enough to allow us to scratch some off with a fingernail.
Next, we tried a medium-grit green scuff ball on a high-speed drill. While this has worked well with raw aluminum, it wasn’t effective on our clear-coated cover.
Next, we tried sanding with 400-grit wet/dry. Fill a bowl with water and add a small drop of soap. The soap keeps the sandpaper clear when you dip it in the water, and the water lubricates the sandpaper and keeps it clear while you’re sanding.
Now we’re getting somewhere. It took about 20 minutes to get to this point, and the dull parts show we still had a ways to go.
Once we had the entire cover sanded, we rinsed it thoroughly and then put it to a Sisal buffing wheel, using a brown compound. The results were immediate and impressive.
While buffing, clean your buffing wheel regularly. Metal gets bound in the compound and can abrade surfaces more than you’re looking to. A simple trick is to wrap a hack saw blade with duct tape and carefully stroke it across the spinning wheel.
After buffing our cover with brown compound, we used wadding polish to remove all the wax before giving a final buffing using white compound. You can see the finish is really starting to come up.
Once we finished with the buffing wheel, we hand-polished the cover with Mothers Mag & Aluminum Polish to get a nice, even luster. There are still some visible scratches, suggesting we should have done a finish-sand with 600-grit. That’s a lesson we’ll remember for the next time.
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