I know that some of you are getting tired of this topic. However, I find it interesting. It is one of the major R's of our hobby: Riding, Reading/Research, and Restoration/wRenching. My interest in the discussion was recently piqued by the original Cinelli Model B that is currently on E-bay, contrasted with the current thread on restoration of a Cinelli SC that had been butchered by a previous owner:
I really like the looks of the Model B currently being auctioned. If I wasn't running out of room, I would probably be a hard bidder for this bike. I would opt toward preservation, for the many reasons that have been hashed and re-hashed on the list. Most significantly that once restored, a bike loses the marks of its history, its originality, and often its heart and soul. (what the hell does he mean by that?)
Having said that, I can verify that once rust bubbles up through the paint (like on the Model B Cinelli on E-bay), there is always a lot more where that came from, beneath the surface of the paint, slowly eating away at the metal below. Hard to stop, I think, no matter how liberally you coat with wax.
If restoration is required, my own preference is to match the factory finish, chrome accents, and decals as closely as possible. This is a time consuming process, and one typically not economically delegated to your $100 per hour (or more) painter. I have spent hours in paint stores (and just outside the paint store standing out in the sun light) matching paint colors and the grain of metallic paint to get it as close to the original as possible.
Careful stripping of paint and media blasting are also important to maintain details of the original metal work (ie. the Campagnolo stamp in the drop outs). I have found that most painters apply modern paint, and especially clear coat, too thickly in comparison to original finishes. Sometimes lots of primer coats are used to cover residual pitting left on tubes that have suffered rust damage. Clear coats need to be severely reduced to give the same flat luster (sounds like a contradiction) that was common on original paint. Also, getting the decals right can be a challenge. As has been mentioned in a recent post, many of the 60's, 70's, and '80's decals were never cleared over. Finding reproduction decals that are accurate often requires buying multiple sets from different suppliers for comparison with the originals (if you can). And/or working with a patient decal maker (like Mr. Softley or one of the guys at SSIink) to get every detail correct.
All too often, I have seen frames "restored" (sometimes by expensive high-end shops), with formerly chromed details (ie. fork crowns, drop outs, lugs) painted over, fixed with terribly bad reproduction decals or simply the wrong decals, and nearly always with a clear coat over the top. The finished frame looks nothing like it did when new. Really no need to mark it with the painter's "tattoo" to avoid any deception. No enthusiast who knows anything about vintage bikes would ever mistake it for original paint.
As far as value, I believe when it comes to bicycles, there is no comparison between what someone will pay for a clean original paint bike versus a re-painted restored bike. If the re-paint is done to a high standard (ie. in keeping with the original finish), the differential may not be as great. If not well done, the repainted bike may bring less than a tatty but original paint bike. We will see where the Model B ends up, and compare with a recent auction for a repainted 1971 SC complete with 50th group that never made opening bid of $2,500. (yes not really an apples to apples comparison but still interesting):
I found it funny that John Barron recently (correctly) identified a very high priced E-bay Cinelli (owned by a friend of Greg Softley's) as having original paint by noting that the serial number on the bottom bracket shell was badly filled with red paint, and that no restorer would do it so sloppily. Cinellis have the epitome of thin paint. You can see the file marks on the fork blades through the paint. This is probably why most have rust issues on the top tube. (sweat just eats right through the paint). Generally, there is no clear coat over the decals. Metallic content is so fine it looks almost like paint from an aluminum spray can. I have an original paint SC with a ripple in one of the world stripe bands! So, they were not that perfectly finished, and care must be taken not to "over restore".