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Chemically Coloring Mahogany Strat with Potassium Dichromate

Cagey

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I finally got around to routing out the pickup cavity for a humbucker at the bridge position on a mahogany Strat body I bought some time back, so it was time to start finishing the thing.

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You can see how the wood has started aging already by where the wood is fresh cut. I think the thing's over a year old, maybe two, and still raw.

I debated all sorts of finishes on the thing, from gloss black to tobacco burst to wipe-on oil over stains or dyes until I finally read about Potassium Dichromate. It's known by several names such as Bichromate of Potash, Dichromic Acid, Dipotassium Salt, and Dipotassium Dichromate but they're all the same thing. It's a natural chemical that is good for a number of things, but for woodworking it can rapidly "age" woods that are heavy in tannins such as cherry, oak, walnut and especially mahogany.
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It doesn't take much of it to get the effect. An 8oz bag as shown above is probably a lifetime supply, at least for me. Opinions vary as to how much you need to use, but between a teaspoon and a tablespoon to a cup (8oz) of hot water and you've easily got enough to do 3 or 4 guitars. I put about a tablespoon into about 10oz of water, and this is what it looked like...

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Apparently, the stuff is quite toxic and will cause contact dermatitus that's difficult to treat, and is especially hard on the eyes and lungs if any gets in them from the dust or splashing. Cancerous as hell, too. All that fun stuff. So, wear all the appropriate protections (rubber gloves, eye cover, breathing mask, apron, etc.) and watch what you're doing. If you're interested, there's a Material Safety Data Sheet available.

I applied it with one of those cheap sponge "brushes" you can get in 6 packs for about $4. You can see the tip of it to the lower left of the poison in the upper picture. Since it's water-based and goes on kinda thin, it appears to dry pretty quick. With one application, this is what I had after about a half hour...

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As usual, it's not as impressive in the picture as it is in real life. But, it's nice. The quality of the grain is preserved in a way that isn't with stains and dyes. I expected it to be more reddish, but it may just be that particular chunk of wood. I'll see what it looks like in the sun tomorrow, once I start with the beauty finish.
 
THat looks like a very cool undertaking, Kevin - looking forward to further developments, and natural daylight photos.

Bagman
 
Interesting, thats looks great Cagey. Once you are finished, how to you go about removing any residual Potassium Dichromate from the body?
 
These guys say just let it dry overnight before applying tung oil (finish application starts at about 1:45 or so):

http://www.diynetwork.com/videos/egyptian-dresser-ep.-2-part-4/27199.html

Not sure what happens with lacquers or other hot finishes.
 
nexrex said:
Interesting, thats looks great Cagey. Once you are finished, how to you go about removing any residual Potassium Dichromate from the body?

I'm curious about that, too. I'm not sure you have to. Nobody seems to talk about it that I've been able to find. So, I think what I'm going to do is put on all the protective gear again and take some 0000 steel wool after it, then wipe it down with a water-dampened rag to get rid of the major dust. Give it a couple hours to dry well, then take some 400 grit after that since the water may raise the grain again a little bit, then I'll hit it with a tack rag to take that dust off. Then, I'll wipe it down with naptha, let that boil off, and put on a coat of sanding sealer. That ought to do it.

I don't want to clean it with anything volatile while it's dusty, because it's an oxidizer and there's a slight risk of spontaneous combustion. I've read you have to be careful where you put rags/brushes/applicators that have the stuff on it where it might contact things that are highly volatile, such as other rags with cleaners on them. But, once it's finally sealed, I think it'll be safe to play with.

At that point, I'm torn about what to do with the grain pores. I'm going to put Behlen's Master Gel polyurethane on as a final finish coat, which is supposed to level out pretty well on its own. But, I don't know how well it fills. I have some clear grain filler from Colortone, but as I've mentioned before it's pretty thin stuff. I really don't want this to turn into a never-ending project where I sand and fill for weeks on end before getting into the final finish steps. I've got to move in 3 weeks, and I'd like the thing to sit a while out in the open before I put it in a case.
 
bagman67 said:
These guys say just let it dry overnight before applying tung oil (finish application starts at about 1:45 or so):

http://www.diynetwork.com/videos/egyptian-dresser-ep.-2-part-4/27199.html

Not sure what happens with lacquers or other hot finishes.

That was an interesting video. But, they seem to gloss over some of the details about the Potassium Dichromate. Or, maybe I'm just taking the MSDS too literally. I know if you read those data sheets on acetone, naptha, MEK or any of the many chemicals that we use all the time in finish work and just take for granted, they're pretty scary, too.
 
Cagey said:
0000 steel wool

Speaking of toxic ... :p

What have you got against white scotchbrites?
I discovered those during my last ( and first actually ) build and put my bag of steel wool in the garage where it belongs ... only to be used on rusty tools etc. and outdoors.

And as far as the Potassium Dichromate goes ... isn't there a safer way to get the same look?
 
I just happen to have some steel wool around, and don't have any Scotchbrites at the moment. Next time, for sure, as I don't appreciate the detritus steel wool leaves behind. It's like packing peanuts or hardwood sawdust or sandblasting sand, only much, much worse.

As for a safer way to get the same look, no. Not really. It's a whole different process. Besides, most finishing chemicals are highly toxic and/or cancer-causing. We just don't think about it. Familiarity breeds contempt, and all that. I just happened to look into it with this stuff because it's out of the ordinary for me.
 
Interesting thread.

Thanks for sharing.
It's stuff like this that keeps me coming back to this forum.

I'll bet that is going to take on a whole new dimension with some clear (whatever you end up using).

Keep us posted.

James
 
Well ... I'm planning a build with a mahogany body and I like how this is looking so far.
Please keep us updated with pics!
 
Watershed said:
It's stuff like this that keeps me coming back to this forum.

Same here. No matter what you think you know, there's always a new failure or success to add to your knowledge base so you can improve your own art.

Watershed said:
I'll bet that is going to take on a whole new dimension with some clear (whatever you end up using).

I'm highly encouraged by what I saw when it was wet.

The neat thing about this process is that it doesn't cover anything up or add anything to the wood. It simply emphasizes its natural appearance as time would affect it. So, you keep all the inherent character, figure, depth, etc. Plus, it's not a particularly "surfacey" sort of thing. It's in the wood itself, using its own chemistry, kinda like a natural tan vs. a spray-on tan for going to the beach. It's subtle, but noticeable.
 
Steve_Karl said:
Well ... I'm planning a build with a mahogany body and I like how this is looking so far.

Be aware that there are differences in how mahogany from different areas responds. Philippine, Honduran, African, West Indian varieties will all return different colors ranging from brown to rust to red. I'm not sure what this body is made of; perhaps somebody at Warmoth could speak to that. In any event, I can't imagine being disappointed.
 
I finally was able to get back to this today. I followed the plan I described earlier with a minor modification. I knocked it back with steel wool, and cleaned it up with a water-dampened pocketless t-shirt shop rag, took some 320 grit after it once it dried and cleaned that up with naptha, but before putting sanding sealer on it I decided I didn't like the way the end grain looked. So, I mixed up some tobacco brown dye w/ 100% alcohol, opened a beer for myself so the guitar wouldn't have to drink alone, and darkened the edges of the thing, just slightly blending it into the front/back like a burst sort of a thing, but not that pronounced...

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Is there anything beer can't do?

As it works out, I probably should've added some black to that tobacco brown. Or, maybe just some more brown. Anyway, what little burst effect there was got lost when I put on the sanding sealer...

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Isn't that an oogy mess?

...because the raw wood darkened up on its own a bit, diminishing the contrast between the dyed areas and the raw wood. But, I can live with it. Hadn't intended to burst it anyway; that was just a leavening move to even out the end grain appearance.

We'll give it a few hours to harden up, then start punishing it with the sandpaper again and see how things look.

Incidentally, the sanding sealer is brushed on; that's why it looks so ragged. Also, the apparently wild difference in color between these two shots isn't real. It's due to the first shot being in normal shop light (this is a bright shop), and the second one had the camera's internal flash on.
 
You got all of the necessities on the work bench including the beer. It's coming along quite nicely. :eek:ccasion14:
 
Thanks. Y'know, beer's not just for breakfast any more. It goes well with finish prep, and equally so with staining and sealing. Today, we'll find out if it enhances Behlen's wipe-on polyurethane <grin>
 
clewnii said:
Lookin good there dude.

Well, the coloring is, anyway. The in-between steps with sealers and fillers don't make for very attractive surfaces right away. But, that'll change as it progresses.
 
Well, after several false starts, life, and other intervening complications, I finally made some progress on this thing.

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The edges aren't as dark as they look in these shots; the camera was getting tricked by the sunlight in the background. They're actually about the shade of coffee. It's a transparent tobacco stain. It's also a bit wider around the edges than I planned, but what the hell. It's still purty. Now comes the waiting until buff/polish.
 
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