Railroad lanterns were used outdoors, so bumps, rust, soot and grime are usually the rule and not the exception. Some were painted by their owners to try to prevent rust. There are many different ways to clean the paint and rust off lanterns, but it's best to use a citrus-based solution, which is safe on any kind of metal, whether it is tin, aluminum or steel, unlike lye, which is dangerous to use on aluminum.
Examine a lantern before you buy it, as cleaning can only go so far to restore it. If pieces are broken, or need soldering, you may need a professional to help restore your railroad lantern.
Use a damp rag to clean away dirt, dust, soot and cobwebs from your lantern.
Disassemble your lantern. Take apart the globe retainer and retainer spring and the font, remove the burner from the font and detach the clip-on or twist-on bells. Place these items in a 5 gallon bucket for safekeeping.
If you have doubts as to how to reassemble when finished, sketch out the elements and where they go on the lantern.
Apply a citrus-based paint stripper to old paint on your lantern following the directions on the bottle.
Clean with water and dishsoap. Rag dry thoroughly.
Remove any rust using a rust-removing product for metal surfaces, following the instructions on the bottle. Use it on the lantern as well as its pieces.
Clean with dishsoap and scrub with four S.O.S. steel wool pads.
Wipe dry with a rag and use a blowdryer for 30 minutes or until completely dry to avoid any new "flash" rust from forming.
Modify any parts of the lantern you wish by purchasing replacement parts. However, mark the replacement part with a small tag indicating it is a replacement and the date it was replaced so that, if you sell the lantern in the future, the collector has the lantern's complete repair history.
Solder any holes or broken parts with a soldering iron and solder.
Put all the pieces back together again.