Chrome, foil, and four evenings of rust
The fork and the rear triangle of this frame are chromed, or were, and when the bicycle arrived they were mostly a crust of brown and orange with chrome visible underneath in patches. I had read that aluminum foil and water would take surface rust off chrome without scratching it, and I did not believe it, so I tried it on the least visible part of the left chainstay first.
It works. A ball of kitchen foil, dipped in a bowl of water, rubbed over the rust with moderate pressure. The foil is softer than the chrome but harder than the rust, and the water carries the oxide away as a gray slurry that looks alarming until you wipe it off and see bright metal underneath. The first 10 cm of chainstay took about fifteen minutes and went from brown to mirror. I then did the whole rear triangle over two evenings, roughly four hours total, and the fork over two more.
Where it does not work is where the rust has gone through the chrome and into the steel beneath. Those spots, and there are about a dozen on the fork crown and the dropouts, come up as dark pits rather than bright metal. I cleaned them as far as the foil would go, then went in with a small brass brush, then wiped the whole area with a solvent and sealed the pits with a thin coat of clear paste wax. They are visible if you look, and I have decided to leave them visible. Replating the fork would cost more than I am willing to spend on a bicycle that is going to live outside sometimes, and the pits are honest.
Practical notes for anyone doing this: wear gloves, because the slurry stains fingers for days. Change the foil often, because once it tears it starts to drag rather than polish. Keep a second bowl of clean water for rinsing. And do it somewhere with good light, because the difference between a stubborn patch of rust and a pit that is never coming out is hard to see under a single garage bulb. I found three “stubborn patches” on the fork that turned out to be pits only after I had spent twenty minutes on each.