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I've been working on a '49 Gibson J45 that has been well thrashed. The goal is to turn it back into a player, not restore it - it was just too crunched up. I've got the splits in the back and the sides fixed and glued the back on. Unfortunately the guitar needs a new top, a previous owner sanded the finish off of it and it was too thin to use. Someone had refinished the guitar with what looks like spar varnish.

I'm not real happy about the glaring white color of the spruce on the new top and I would like to darken it some. I've tried doing that with shellac before and it just made it look kind of yellow so I was wondering if I could treat it with potassium permanganate so it would oxidize the top? I've used the potassium permanganate successfully on replacement braces and such but have never tried on such a large area. My tests on scrap are encouraging but not conclusive.

The final finish will be shellac.

Anyone have any experience trying to do this?

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Steve Smith
"Music is what feelings sound like"

Fortunately I got more response at the MIMF. Apparently very few folks have experience with potassium permanganate so I get to pave the way. Last night I brushed a dilute mixture of the potassium permanganate and distilled water on both sides of the top. It changed the color but it happens so fast that it is difficult to brush evenly. Spraying would probably be better but great care would be needed as this stuff is a strong oxidizer and you want to be careful where any overspray goes. I will post as I go if only to get it in the archives here.

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Steve Smith
"Music is what feelings sound like"

So the color came out good but it was blotchy because of the uneven application of the potassium permanganate solution using the brush. The color was thin so it was easy to sand off. I'll wait until the top is braced and on the guitar before I try again. I think using a very dilute solution in a spray gun would allow more control and since it is so easy to sand off I'm not so worried about ruining the top. I also did the back since when you wet one side you should also wet the other side; it also came out blotchy but I'm going to leave because I think it will look "right" inside the box - and I don't want to sand off my brace layout

Another idea I received were to use a dilute mixture of tea or coffee (I suppose whatever is the morning beverage of your choice) but I have not tried this yet. I have lots of cutoffs from tops so I'll prep a reasonable sized piece and try this too.

Of course several folks have recommended I put the color in the finish base coats and then cover with clear. This may even be the best idea and is something I've done before so I'll save this as the fallback.

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Steve Smith
"Music is what feelings sound like"

Don't know if you've seen it but Stewmac has a Youtube of /Mamie Minch oxidising new Spruce parts and lightening dark cracks/pick wear on an old guitar top here:
[youtube]https://www.youtube.com/watch?v=tViTWUL8Was[/youtube]

Thanks Mark - Yes, I have seen that. She has a few good techniques for dealing with trouble spots on older guitars using both potassium permanganate to darken and oxalic acid to lighten the wood.

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Steve Smith
"Music is what feelings sound like"

If you could do it without warping i would say leave it out in the sun. Everytime i have left some scrap in the sun it really deepens the color of light wood.

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久保
美智え

Leaving it in the sun would probably work too but I would have to leave it somewhere outside and I'm afraid it would get damaged.

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Steve Smith
"Music is what feelings sound like"

I use water based dye frequently. I apply a light water washcoat as a preconditioner. The dye goes on more evenly. Maybe this would help with your application.

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wah
Wah-wah-wah-wah
Wah

Dan, do you spray your dye?

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Steve Smith
"Music is what feelings sound like"

No, I just wipe it on. Oh yeah, I wet the top, let it dry, and then sand after the grain is raised before I apply the dye.
Of course, I am just a beginner, so I may be doing it all wrong.

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wah
Wah-wah-wah-wah
Wah

Put it in a tanning booth.

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Lance Peck

A few years ago I could have done that easily. Now I don't anyone that has a tanning bed anymore

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Steve Smith
"Music is what feelings sound like"

Deteted the double post and added:

I decided to brace the top and glue it to the box and finish the binding before I try to spray it with the potassium permanganate solution. Finished shaping the braces last night so should get it done in the next few weeks.

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Steve Smith
"Music is what feelings sound like"

Last week I managed to do some tests with the potassium permanganate. First shot is with a brush and it's just not a viable method for application for large areas, in my opinion. Second shot is sprayed on with my old detail spray gun. Potassium Permanganate is the same mix in both photos, mix is a medium purple - probably about 1 teaspoon of powder to 1/2 quart distilled water. Sprayed in one application.



Sprayed on looks very promising. Shading was very easy to control, much like spraying tinted shellac.

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Steve Smith
"Music is what feelings sound like"