Many thanks to Miika Niemimen for this excellent tutorial. Miika's guitar project which cover was made for can be found here on the forums: Real gold top Les Paul
Hi folks! Thought I'd share what I created yesterday. I'm working on a gold top LesPaul (haven't updated the build thread lately, will soon).
Well, I wanted to make a custom trussrod cover with my own graphics and using material that would match the gold tuners and overall gold theme of the guitar. Brass looks very much like gold when polished so I went for that, but you could use other metals.
I recently learned an etching technique to make metal signs so I used the same method here. The technique is similar as making circuit boards so I'd start the search for chemicals at your local electronics component store. Sounds complicated and, yes, it does take a little testing but not very difficult at all. OK, I could have taken the brass plate to be CNC'd but that's really not my point - I really respect handcraft and want to do things by myself.
So here's the way to etch if you want to try it for your unique trussrod cover, or customize any other metal part on your guitar (metal pickup covers, pot knobs, scratch plates, neck mounting plates - you name it). WARNING: Be careful with those chemicals! Use protective gloves, don't breathe the fumes, don't mix them and dispose properly (not in the sink!)
Develop the exposed plate in sodium hydroxide (NaOH) solution (7g/litre of water). The exposed lacquer will dissolve in a few minutes and the unexposed will protect the metal from dissolving in the next phase.
Treat the plate with ferrichloride (FeCl3) solution for about 1 hour (500g of FeCl3 granules per 1 liter of warm water). Look at the plate every now and then. If some part is not dissolving correctly use a needle to scratch the excess lacquer. If a protected area is eroding use the marker to protect it and you may be able to hide the flaw in the polishing stage.
Polish with fine grit paper (I used 2000) and a woollen sock. Reapply gun blue and polish again if you're not satisfied with the darkness. Trim the plate edge with tools of your choice (eg. Dremel, file and sand paper). A layer of lacquer will prevent the brass from oxidizing.