Reoxidizing rosewood

[David Houchens]

I'm working on a 1986 D28 that had a large (fist size) hole knocked in the back. Somebody tried to put the pieces back together. A few small pieces were missing. I took the pieces back out to get a more level surface.  I've got the pieces back in and as level as they would allow. While level sanding the repair, some of it went through the finish. Rather than the brown,aged look of the rest of the rosewood on the guitar, these spots now look like (what they are), freshly sanded rosewood. I tinted my lacguer a little but as I thought it would, it only made the wood darker. Has anyone had success bleaching or oxidizing rosewood to match older wood?

[Mac Walker]

I asked the question about oxidizing mahogany in order to darken here:

http://fretsnet.ning.com/forum/topics/what-causes-honduran-mahogany...

From wikipedia -

"Wood treatment -
Potassium dichromate is used to finish certain types of wood. It brings out the color and grain to a very deep, rich appearance. This is particularly effective on mahogany.[4]"

I tried it on a piece of scrap mahogany and it worked well. I can't speak for how well it works with rosewood, a quick google search didn't reveal anything either, hope this helps....

[David Houchens]

Thanks Mac. I do remember reading about that on a violin site. I googled it and it was listed as an art supply in one place. I'll try the local shop.

[Howard Klepper]

So the older wood under the finish is lighter? I'd recommend you not try and bleach or oxidant; you are like to make it worse. Time will heal it.

[David Houchens]

Howard, Just to see if we mean the same thing, the wood that is still under the finish is lighter than the fresh sanded wood where I went through the finish leveling the repair. So you suggest to just finish over and let it lighten with age? The guitar is 24 years old. Although it may have been this light for years, I would think it would never catch up, unless there is a limit to how light it can go. And even then, wouldn't it take years?
Not arguing understand, I realize time is how it got this way but not being a collectable guitar I was hoping to improve the looks of the repair somewhat. It is such difference in color that it looks really bad. I ordered some Dichromate from Int. Violin today. It was only $5 so if I end up not using it it won't be a great loss. I'll try to get pictures up tonight if I can. Got a sinus infection going on. Kinda feel like " some sonofagun has killed me with a brick". Love that Grayson and Whitter.

[Frank Ford]

I've yet to find a decent solution to this problem - every kind of bleach I've tried has been disappointing.

Here's a tip you might want to try as you're messing around with touchup. If you want the finish to darken the wood as little as possible, try sizing the raw wood with hide glue first - you might get a nice surprise. . .

[Howard Klepper]

Potassium dicromate does an effective job of darkening mahogany. I've never heard of it being used on any rosewood, but I'd sure be surprised if it lightened it. The thing about bleaching an area is that it always comes out splotchy, and it's even more likely to do that if there is lacquer on the rest of the back. I guess that someone somewhere has done this successfully, but I haven't seen it.

Either lacquer the repaired area and wait for it to even out, which may take years and a bunch of sunlight, or sand and refinish the whole back. Which may lead to sanding and refinishing the sides, too, if they are a lot lighter.

Lacquer (unless it is toned or has yellowed) doesn't actually darken wood. It reduces specular reflections, which appear to the eye as white light and make a surface look lighter.

[Howard Klepper]

I meant diffuse reflection, not specular. The edit button on this website doesn't work for me on my Mac.

[Howard Klepper]

Hmmm, actually, it is the specular reflection that often appears whitish. The lacquer reduces the whiteness by concentrating specular reflections in particular spots. Isn't the Net wonderful?

[David Houchens]

Thanks Mac,Howard and Frank. I will try franks tip on sizing it with hide glue first and go with that or just sand out the whole back. I appreciate you sharing your knowledge on this subject.
I'll save the dichromate for...well ..something....maybe.
Thanks again to all

[Kerry Krishna]

I'd like to step in here for a min and talk about Potassium Dichromate. I worked in the soil Science Labs at McGill University in Montreal for 4 years. There were dozens of chemicals that were locked up that only the lab supervisors had access to. In our lab, the most dangerous chemical in that cabinet was Potassium Dichromate. The only better guarded , more dangerous thing in that lab was Radioactive material! I had to receive Haz Mat safety training on it too. Can't breath it, touch it anything... While using P.D. the one time, I spilled one single drop on a countertop. Everything used to clean up that tiny spill had to go into special sealed containers ( that I did'nt even know that we had) and some company had to make a special trip to the lab to pick it up for destruction. And I got in quite a bit of trouble too , let me tell you. As far as Cancer causing agents, it is wayyyy up on the list. It TOTALLY freaks me out coming onto a forum like this and hearing so casually about this toxic stuff. I was allowed to use it only under VERY specific circumstances and only under heavy direct supervision to use it. There was a large thread over on Mandocafe all about this a number of years back. Please find some other way to accomplish what you need to do. I really did think that most everyone on these Forums were aware of the danger of it. Why is that?

[Mac Walker]

I think it's only dangerous in Canada? Just kidding, I had reservations myself when I saw it was listed as a class I Carcinogen. But the reality is that is takes years and years of exposure (i.e. in a leather tanning factory for example) for problems to develop. If proper precautions are taken, i.e. adequate skin, eyes, and lung protections, the exposure risk is non-existent. Probably equivalent to gasoline in terms of its cancer risk. Also it's not regulated in the States like it is in Canada, which should tell you something.

[Kerry Krishna]

Oh my... You are kidding right???