UPDATE POST: 6/21/11
I updated my method and materials somewhat. The initial post below is still a worthwhile read as it leads into the updates I posted here.
INITIAL POST: 11/25/2010
While I don't think my polishing efforts are any better than a lot of what I see here in C&V I get lots of questions via the forum and via PMs about my techniques. I've bounced this idea around for a while and given I'm stuck basting a 20 1/2 pound turkey for the next 5-ish hours I thought I'd start a thread that I could 1) give a description of what I do and 2) keep updated as I find different techniques and ideas.
I certainly hope this doesn't seem presumptious on my part but with the number of questions I get, heck, I figured this would make it easier on me to respond (paste a link baby!) and to give a little more detail than I normally might.
Please keep in mind, what I'm talking about here is how to work on aluminum. For chrome I'm still working things out, there are much better people than I at chrome. I defer.
All the techniques I'll describe here are hand techniques, with the possible exception of the abrasive balls below...but they are used in a hand drill (and most everyone has one) so... You don't need buffing wheels and the like to polish a quality part. Those tools can take time off the process but not necessarily get you a higher quality result. I view my polishing activities as relaxing. Wet sanding is done at the laundry tub but once I get to polishing I have a huge beach towel that I spread out over myself, sit down in the easy chair, and polish while I watch TV and drink a Coke Zero or herbal tea (not a beer fan, sorry ). It's a lovely way to spend an evening.
Some of the different "tools of the trade" that I use:
- Wet/dry sandpaper. I like going to auto parts stores and/or dedicated auto paint stores as they have a wider selection and much finer grits than a hardware store usually does. I've used grits from 220 to 3000. Buy good sandpaper, 3M, Norton...it makes a difference.
- Sanding sponges. Good for long parts like crank arms and such with rounded edges that the sponge can conform to. Used wet. I don't use them all the time but I keep the on hand.
- Abrasive balls (link) in the power drill. I like these for doing an initial "clearing" of the part, more below. I'm also looking for smaller versions.
- Mother's Mag and Aluminum Polish (link). The workhorse of the process.
- Blue Magic Metal Polish Cream (link). Slower working than Mother's but can get a last bit of shine that Mother's doesn't. I'f I'm going for mirror, it's the last thing I use before NuFinish.
- NuFinish Car Polish (link). While I have no empirical evidence for this yet I think a quick wiping with NuFinish protects the bare aluminum somewhat from the elements. I include it here because I'd love some other people to try it and see what their experiences are. I do know that it works well as a quick prep before bike pr0n pics I like it on frames too. I use the liquid.
- Turtle Wax Polishing Compund (link). Used for anodized and painted parts.
There are three categories of parts that I look at:
- Bare aluminum.
- Aluminum that is anodized/painted and I want to remove it.
- Aluminum that is anodized/painted and I want to retain it.
One obvious question is "How do I determine if my part is coated?" There are tests one can do with a multimeter by measuring resistance on the part's surface and other techniques. Googling may help too. What I do is to find an inconspicuous spot, get a rag with a tiny dab of Mother's, and wipe. If the Mother's turns black nearly immediately the part is surely uncoated. Try in a few more spots, especially where the finish might appear different than other places. You may have clear anodizing that has worn off in places in which case the best thing would be to remove it and polish. Of course, if the parts are of "historical" significance or particularly valuable you should take that into account before doing anything to change them significantly. I like shiny parts (although I read with interest about folks using techniques to get to a satin finish) but I'm sure there are parts that should stay as they are and retain their patina to match a particular bike or build. Painted parts should be fairly obvious.
The very first thing I do is clean all parts throughly 1) because I like clean parts and 2) if the parts are clean its easier to see where they need work. I'll use a combination of things, Dawn dish soap, Simple Green, citrus-based, "Amazing" from the dollar store. All have their place and use. Cleaning could be another post all in itself but be careful with cleaners like Simple Green, citrus and the like. If used too strong or in a hot solution (or both) they can really change the look of a part. Don't ask me how I know. I'll just say I had to polish three chainrings I hadn't counted on...
Part of through cleaning is disassembly. I take apart brake calipers, noting things like order of washers and nuts, rear derailleurs (as much as reasonably possible), and other moving parts that don't require punching out rivets or anything. I don't disassemble an RDs parallelogram . Stems and seatposts get bolts removed. Anything that is steel/chrome gets an oxalic acid bath, even if I can't see any rust. When parts are reassembled they get lubricated in all the right spots. It's amazing how much better a 30 year old RD works after just a little care, even if it's been sitting in a co-op parts bin.
Now we know if our part is coated or not, it's clean and disassembled, and the aluminum pieces are ready to be worked. Here we go, forgive me if I ramble.
- The first thing I do now is a pass with one of the abrasive balls. The reason for this is twofold: 1) to remove shopwear and cut surface oxidation and 2) to even the surface to make finding nicks, scratches, and other flaws easier. Depending on the condition of the part I may start with either of the grades of abrasive ball above. I chuck it up in the cordless drill, hold the drill with my right hand, and manipulate the part against the ball with my left. I always finish with the fine ball and I do use them in order, coarse to fine.
- Once I've identified the nicks and other flaws I want to remove it's on to wet sanding. Depending on the depth of the flaws I want to remove I may start with either of 220/320/400. If the part is pretty much flawless you can even start at 600. Sanding the flaws can be tricky. To remove the flaw you need to remove material but you can't concentrate your sanding locally in one place. If you do you run the risk of "scalloping" the part...having visible depressions in the part once it's highly polished. I alternate between short local strokes and long strokes over a bigger section of the part, centered on the flaw. This is one reason I'm against using Dremel-type tools for this work. It's just way too easy to remove way too much material quickly, and locally. Hand work takes longer but is "safer" IMHO.
- I continue wet sanding using increasingly fine grades of sandpaper, all in order: 800/1000/1200/1500/2000. I'll sand lengthwise with the part, then at 90 degrees. This allows you to work the part faster....sanding creates fine scratches in the direction of your stroke. By switching directions you cut across those scratches which are removed more quickly. If you try you can feel the pull of the paper change, or I can by now. This is also a way to determine when you're ready to go to the next finer grade. The paper will feel different. I use a lot of paper and switch as soon as I feel the grit is becoming worn. Another thing that helps, especially when you get to the finer grits and you're more polishing than sanding, is to presoak the paper in water so the paper gets more flexible. The finer grades then can act more like a rag than stiff paper. It helps get into inside curves better.
- I'll usually stop at 2000 grit anymore. I think it's a good balance between smoothing the part well in prep for polishing and not standing over the laundry tub any more than needed. My tub needs to be 6 inches higher! Stop at 1500 and you'll polish longer, go to 3000 and you'll spend more time sanding. It's a trade off but I've found that 2000 works well and is readily available, finer grits can be hard to find sometmes. I have gone on to 3000 grit as an experiment. If you work it right it can create a nice satin finish but it's hard to do evenly on parts with lots of curves. I suspect the Scotchbrite techniques I've been reading about for a satin finish may work better. On a flat part though, 3000 grit gives you a finish much like that of Nitto Pearl parts.
- Once all the wet sanding is done: flaws removed (or diminished as much as possible), surface left nice and even by the 2000 grit paper, it's on to polishing. I start with Mother's. Dab on a rag and just start rubbing. ASIDE: On the subject of rags, I bought like 200 of the red shop rags at Harbor Freight. This differentiates them from anything of my wife's. I save them up until they're just about all dirty then run them by themsevles in our HE washer on the "sterilize" cycle. Dry them and they're ready to use and my wife and I don't argue about rags anymore I keep one rag specifically for applying the Mother's. I then have several for buffing off the Mother's and I keep one or two handy for buffing once the Mother's is removed. I keep track of them and use them only for those purposes for the duration of the current polishing session. Eventually one of the ones used for buffing off the Mother's gets slightly impregnated. This is a magic rag. Once you get one of these it's the one I use to see where I am once I think I'm about done with Mother's. There's something about that light level of impregnation that works.
- If I'm going for a real high shine I'll use the Blue Magic after I'm all done with Mother's. It works slower but I think it imparts just a tad higher mirror shine to a part. I don't like the smell so I use it sparingly. I love the smell of Mother's it reminds me of working on bikes
- At this point I'll wipe the part down with some liquid NuFinish and it's done. Lube, reassemble, stop and admire your work.
Aluminum that is anodized/painted and I want to remove it.
- Removing anodizing or paint can be done physically (by sanding, lots of work) or chemically (with some lye-based cleaner). The lye-based product I use is Easy-Off oven cleaner, or generic equivalent. It's convenient, easy to spray into nooks and crannies, and you can use only what you need...no containers of lye hanging around. Please, Please, PLEASE, read all the cautions, look up an MSDS, whatever. Use the stuff responsibly. Protect your workspace! To use it just spray the part evenly, wait a minute then rinse off. See what it looks like. Different coatings will require more treatments, longer treatments, or both. You'll have to figure that out via experience.
- Having clean parts is paramount here as if you have grease, oil, or dirt on your part the lye won't work there, or work to a lesser degree, and you'll have a mess of a surface.
- Once you have your coating removed you may have a black mottled surface. No worries, don't have a heart attack! See above and follow all those steps now that you have a bare part.
Aluminum that is anodized/painted and I want to retain it.
- If you've decided you want to keep your anodized or painted parts the best you can do is to clean them well. There's really not an "anodizing" polish I've been able to find. If someone knows of one, by all means, please post it!
- In the case of anodized parts I'll clean them well and just wipe them down lightly with the Turtle Wax Polishing Compound. I think the compound is just abrasive enough (EXTREMELY FINE) to remove and pesky oxidation that will come off, yet isn't aggressive enough to visibly scratch the anodizing. For instance, the Dia-Compe 500G calipers on my Fuji America...they are clear anodized and the anodizing was slightly dull from age. I went at them with the polishing compund and the surface evened out and took a tad of a shine to it. I'm sure they're not what they looked like from the factory but they looked very good without going through the trouble of removing the anodizing and starting from scratch.
- For painted parts treat them like you would any other paint you want to restore...polishing compound, ScratchX, etc. The white painted stem on my Fuji Tiara looked pretty bad when it came off the donor bike. Scuffed, black streaks here and there, not ugly but not pretty. 2-3 minutes with the polishing compound and then NuFinish and it looked (and looks ) like new.
Well folks, that's about it for the bulk of what I do. I do have two more tips I'd like to pass on though:
- The abrasive balls REALLY excel at one thing, refreshing seatposts. It always drives me nuts to have zig zags...plain posts are easy, just sand and polish. But, if the post has the machined ridges in it (are they called something?!) around the circumfrence of the post you're talking about a LOT of sanding to get that kind of post smooth and shiny. The abrasive ball, worked parallel to those ridges works WONDERS in reducing the appearance of the zig zags without significantly harming the ridges. You just have to try it sometime. And, at the end, no polishing tends to be necessary.
- Change sandpaper often. I mentioned it once before but I will again. There's no sense in trying to work a part with worn sandpaper. It's not expensive and fresh paper is so much more able to remove material. I dislike spinning wheels!
PLEASE, feel free to add to the thread. One of the things I want to experiment with is the various techniques to impart a satin finish. As I do and get some results I'll be sure to update my post here at the start of the thread. Unfortunately, taking pictures of different surface finishes is nearly impossible. If I get to that point I'll try some nice cloudy day pics to see if one can discern differences.
So many people have different good polishing ideas and techniques. Let's get them all into the same place! Now, that I've started this thread about aluminum polishing I'd like to ask that someone good with chrome, someone good with OA, and someone good with frames and paint restoration do the same.
If you've read this far I commend you! Please ask questions and post your thoughts and ideas. I always like to hear how other people do things.
Cheers and Happy Thanksgiving!