High iron content varnish.

[NickyBass]

I've heard that the top of late 19th century stringed instruments can turn almost black because they used a varnish with a high iron content. Is there truth to this? And if so, can it be restored to it's lighter color while keeping the integrity of the original varnish? How much would it affect the value if one where to have the top completly refinished? I know on vintage slab basses, it's borderline blasphomy. Does the same hold true for DBs?

[mje]

This got me reading about varnishes, especially the article here:

http://www.scavm.com/Fulton.htm

I suppose this could happen if red iron oxide (Fe2O3) was converted to black oxide (Fe3O4) whcih can happen in the presence of heat and CO, or moisture, or perhaps in an acidic varnish, or...?

I can't imagine how you could convert it back.

[nicklloyd]

Originally Posted by NickyBass

I've heard that the top of late 19th century stringed instruments can turn almost black because they used a varnish with a high iron content. Is there truth to this? And if so, can it be restored to it's lighter color while keeping the integrity of the original varnish? How much would it affect the value if one where to have the top completly refinished? I know on vintage slab basses, it's borderline blasphomy. Does the same hold true for DBs?

There are countless old, valuable basses with dark varnish. Oxidation takes it's toll, and the bass turns black/dark brown, etc. I would not vote for a refinishing job, as a rule of thumb.

[NickyBass]

Hey, thanks for the replies. I wouldn't refinish an instrument unless absolutely neccesary. I was just wondering how it would affect the value. In this case, just the top has darkened, and the back and sides are more of a dark cherry color. It looks a bit odd. Not a big deal though. I was only hoping that something non-invasive could be done. So, nothing can fix oxidation then? Oh well, as long as it sounds good.