MIMF

I am 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. Anyway, the guitar is getting a new top, unfortunately, and I'm not real happy about the glaring white color of the spruce. My question is: can I treat it with potassium permanganate to age the top? I've used it successfully on replacement braces and such but have never tried on such a large area. My tests on scrap are encouraging but not conclusive. Hopefully one of you has been down this road and can provide some insight. Thanks.

put your finish on it and let it sit in the sun .
or use a uv light .

I would probably mix some tint of amber and/or brown with lacquer or whatever finish on the first few coats. Experiment on scraps. Sunshine will oxidize the wood and also a lacquer finish, but it just takes longer!
Good luck. It looks like an interesting project.

Since you will need to raise the grain before you apply the finish you can use tea or diluted coffee to stain the new wood. You need to get the surface well and evenly sanded and blemish free before any color is added, because any irregularity in the surface will take up stain differently than surrounding area. Test on scrap first to find the concentration that leaves the right amount of color. Don't try to take it all the way to "old" , just put some bit of color on it and then you can always add some tint to the finish if you find it needs a bit more when the finish wets the surface. Wetting the surface with finish usually darkens the color a bit so don't go overboard in the staining. Try it on scrap first.

Is there light colored binding? If so it is easy to add a bit of color to the finish and spray over the binding, then lightly sand the corner edges with 1000 grit or so to approximate the years of wear. Clear over that.

Thanks for the input everyone. I'm pretty comfortable with using color in the finish but was hoping the potassium permanganate would give a true aged look. I will test some diluted coffee (I've used that before on bone) on a cutoff. Michael, the binding will be light colored so I will try your technique there as well. Looks like I will go with nitro instead of a shellac finish because I will be more comfortable with that when putting on multiple layers of color.

Never heard of using potassium permanganate to age spruce, but I have used it a lot in my day job, including lab work and environmental field work. The solution starts out as very purple and it has a strong oxidizing effect, similar to hydrogen peroxide. It degrades organic compounds which may be responsible for the aging effect. However, the purple stains maybe somewhat permanent. I would go with the tea/coffee recommended by Michael, or a dye tint.

Potassium permanganate should work O.K. to "age" the surface. Use a dilute solution and wet the top thoroughly to get a uniform color. The solution works better on some woods than others so you may or may not like the effect. A light sanding can remove some of the "color" and flatten any raised grain.

I've used the potassium permanganate to age patches and new braces - it works pretty good, the purple color goes away as the wood oxidizes. At least I can make a new patch look like an old patch I will admit I'm mostly nervous about using it on the whole top since it's such a large surface area. I'm already in the hole on this repair and don't want to add another top to that.

Based on your comments I'm leaning towards this approach: Mist the top with a dilute solution of potassium permanganate and watch it as it changes a bit at a time. If I don't like where it's going I will sand it and go with the tea/coffee or tint the finish.

FYI Mamie Minch did a little video for StewMac which shows it pretty well. She also uses Oxyalic acid as a bleaching agent.

A J-45 should have a sunburst top(the J-50 was the natural top), and if you do that, it will look "right".

Mario Proulx wrote:A J-45 should have a sunburst top(the J-50 was the natural top), and if you do that, it will look "right".

I thought about that but the owner said he liked the "natural" look. Apparently this belonged to a buddy of his who went to Vietnam and didn't make it back so he has a strong sentimental attachment to it (otherwise it wouldn't have been worth fixing in the first place).

I went ahead and brushed a dilute solution of potassium permanganate and distilled water on both sides of the top last night. The color changes quickly when you brush it and it is hard to keep it even but it looked pretty good. The water doesn't dry fast but the chemical reaction happens about as fast as sprayed shellac flashes off. Depending on how it looks when it is completely dry I might sand it back some and try spraying a coat.

Using the potassium permanganate the color came out good but it was blotchy because of the application with the brush. Fortunately, the color was very shallow so it was easy to sand it off. I'm going to wait until the top is attached to the guitar and I'm ready for finish before trying anything else.

Pre-wetting the top with water and then using the dilute solution may give you a more even affect. Spraying seems like it would be a good way to go, although I've never tried that. I generally apply it with a soppingly wet rag and then immediately wipe it off going with the grain (usually on furniture).

Thanks Clay, it's nice to hear from someone who has worked with it before. I can see where the sopping wet rag would work much better than the brush - I just couldn't keep the brush loaded well enough. I think I will test the spraying method on some cutoffs. If I can get the application to be even then the color change is exactly what I'm looking for.

Any photos of this process? Is this the right kind of stuff, or does it need to be laboratory grade?

http://www.amazon.com/KP02N-Greensand-F ... VX4HUI/ref

I will take some photos but haven't done so yet. I've got the braces ready so will probably glue up the top sometime in the next week.

I don't know enough about this to know if the product you are looking at will work. Here is what I've been using, also from Amazon. http://www.amazon.com/Potassium-Permang ... A2BX46TEBS

Finally some photos of 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.

Recall that this is is a chemical reaction with the wood, and it's pretty obvious where I tried to darken some light areas and that turned out way too dark.

Spraying this on was much like spraying tinted lacquer, pretty easy to control the shading and I like how even it came out. Before spraying it looked like the top next to it.

This video has good instruction about using Oxalic Acid (Barkeeper's Friend scrubbing powder is a cheap option) to bleach some cracks and pick wear and Potassium Permanganate to age replacement Spruce braces on a 100+ year old guitar top. Much more authentic than using stain and dye.
http://www.youtube.com/watch?v=tViTWUL8Was