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re-plating bridges

Discussion in 'Luthier's Corner' started by mss, Oct 29, 2004.


  1. mss

    mss

    Sep 11, 2004
    I have a few gold bridges (1 Kahler, no longer made, and 2 Schaller) and I am interested in having them plated black. Is this at all practical, and if so, is there a specific type of plating I should look for?
     
  2. Hmm, "practical" may mean different things...

    It IS possible to remove the plating and make them black. That's the simple side of the process - stating it. Doing it is another thing. I've done some experimenting and I've found two routes you can go - chemical "blueing" or powdercoating. The blueing technique I've done in an old BAII bridge. This will work as long as the metal is steel. First I sandblasted the chrome finish off of the bridge then I used Hoppe's Cold Blue on the sandblasted piece. I did as the instructions told me and wiped on the finish. This worked pretty well but I would have totallyl immersed the piece knowing what I know now. It's hard getting the stuff into all of the corners. It turned the metal a nice black and etched the surface back to where it was a bit smoother than the blasted one. Once you've done this and it's dry, you should buff it and then clear coat it to avoid scratching. This method will cost all of about $8 per bottle of blueing and you will probably use a bottle per bridge if you totally dunk the entire piece. I've got to warn you though, this method is delicate and can be imperfect in the process. You might have to do it twice to get a perfect surface. The bubbling action of the chemicals can sometimes leave marks in the black surface that are difficult to buff out.

    The other way would be to powder coat the piece. Powder coating is a type of "painting" but it's done a different way. The target piece is prepared normally and then has an electrode attached to it to give the piece a positive (+) charge. The "paint" is actually a dry powdered, thermoplastic pigment. It is sprayed through a special gun that gives it a negative electrical charge (-) and that makes it stick to the target piece. While still charged, the piece is then baked at a temperature that melts the pigment into a solid skin over the entire surface of the piece. Powdercoating is extremely hard and durable. It's been used for decades in the high performance auto industry as an impact and solvent resistant coating that can really take the abuse. So how would you do it at home? Two vendors make consumer powdercoating kits for home use - Eastwood and Harbor Freight. The process is the same, but you would use your kitchen oven to bake the pieces after spraying. These kits (less pigments) are around $100. You could also look for a local source for this process. I would estimate that each piece would run $20-$30 for prep and powdercoating if it were done by a small shop.

    So now you see how volume could affect your choice. If I had a bunch of pieces to do and I expected to do more, I would probably go powdercoating and do it at home. But that's just me and I'm waaay different than most folks. :D
     
  3. mss

    mss

    Sep 11, 2004
    Thanks very much, hambone. It sounds like powdercoating is the thing to do.
     
  4. pilotjones

    pilotjones Supporting Member

    Nov 8, 2001
    US-NY-NYC
    A bit more info- one of the platers my company uses is offering "black zinc." I don't know exactly what it is (such as a variation of the zinc white chromate or zinc yellow chromate conversions), or if it is of high cosmetic quality, but you might inquire about it. Come to think of it I should ask them for a sample some time.

    Ham, do you think powdercoat is tough enough to stand up to having saddle height adjustment screws scraped across the base plate surface as intonation is set (assuming the bridges in question work similarly to a Fender or Badass)?
     
  5. If a smooth, flat bottomed screw is used, then yes, I think It will work fine. This stuff is really tuff and if you don't break through the surface, just doesn't scrape off. Remember, a blasted or chemical etched surface is best for powdercoating. That rough surface helps with the grip. Besides, I'm of the opinion that during the life of most bridges, there is very little movement of the saddles. Once a set of strings is decided on, that keeps things close from that point on.
     
  6. pilotjones

    pilotjones Supporting Member

    Nov 8, 2001
    US-NY-NYC
    Yes, sounds reasonable. The coating is awfully tough, and if the metal surface is prepared to have a little roughness as you said, it will bond all the better. Probably a good idea to polish the bottoms of adjustment screws a bit before use, just to be sure.

    One other thing. If the clearances between parts are very tight, the finished parts might not assemble. Powdercoating adds a few thousandths to each surface. Again, no problem if there's reasonable looseness before coating, though.