Topic: 1950s anodizing project


I am a new member with a restoration project of an old guitar amplifier from the late 50's. There is an aluminum control nob that is missing but I cant quite figure out the finish on it.

I am suspecting anodizing with a subtle bronzish color. Is there any way to confirm that anodizing was the finish used ?

does anodizing necessarily make the surface electrically non conductive ?




Re: 1950s anodizing project

If the color is bronzish, it may be chromic acid anodized.  (aka Type I).  Or it could be simply chromated aluminum using a hexavalent chromate.  Or it could be sulfuric anodized or hard-coat anodized and finished with a chrome-containing sealer.

Do you have any photos to share?

-Dustin Gebhardt, CEF

Advanced Manufacturing/Finishing Engineer


Sanford, NC


Re: 1950s anodizing project

It will be non-conductive if it's anodized.  I would expect that it's anodized given the era.  It may have been organically dyed and after all that time faded substaintially.  But it may have been dyed with FAO, common for electronics at that time, which produces a bronzish gold color.  It's difficult to be sure with any non-destructive test.