Potassium Dichromate (Bichromate) on Mahogany

[tylereot]

Thanks to the unending generosity of Cagey, I've been doing some experiments with that toxic orange stuff: K2Cr2O7.

Using some scrap from my mahogany jaguar project, I mixed up a cup of warm water with a half teaspoon of dichromate.  This was applied to the mahogany in a wide stripe, until it was quite wet.
In 10 minutes, I took this picture:


I then wiped half of that treated area with rice vinegar, and mixed in another half teaspoon of Dichromate into my 1c of water, giving me a concentration of about 1tsp/ 1c.
10 minutes later, it looked like this...


An hour later, everything had mostly dried, giving it a look like this...


Clearly, the vinegar had indeed stopped the process at 10 minutes, where the untreated areas continued to darken.  The Dichromate really brought some contrast to the grain, in addition to darkening it.  I'm going to give it a light sand when it's really dry, and shoot a coat of crappy lacquer over it to see what it gets.  I expect I'll wish it were a little redder, which might be doable with either a drop of red stain in the dichromate (might blow myself up!  :icon_tongue, or perhaps a touch of red dye in the lacquer.

 

[bagman67]

Pretty dang groovy, Tyler.  I foresee happiness in your future with that 'hog.


My own instinct would be to tint the lacquer, if that should be necessary, rather than introduce a new chemical to the K2Cr207 solution - not having any idea what metal oxides or other chemicals in the dye might react.  You could luck out and no harm, or you could wind up with a cruddy precipitate or worse, evolve some harmful gas. 


In any case, it would be hard to judge what the dye or pigment is really doing when you add it to an orange-colored solution, and much easier if you add it to a clear vehicle such as lacquer or poly.


Looking forward to the ongoing experimentation.


Bagman

 

[Patrick from Davis]

Dyes tend to have lots of delocalized electrons, they absorb light where we see it.  Dichromate will kick the crap out of the dye, and oxidize/break the dye molecular bonds up.  Of course concentrations and individual chemicals will behave in their own manner, but that is the generalized pattern of dichromate.  I can't stress this enough, dichromate is bad stuff.  Chromimum ions and very strong oxidizer.  It is something that will burn the hell out of things, and then the chromimum ions (or various chromate forms) are not exactly friendly to biology either.  Please use caution.
Patrick

 

[tylereot]

Yeah, thanks guys.  Patrick, that absolutely makes sense, knowing what little I've read about the Dichromate.  Yeah, extreme caution: gloves, dust mask, goggles.

Here's what happened with a little 320 sandpaper and a shot of the very last of a can of crappy lacquer. 


It does seem to bring out the red in it a little, and clearly darkens the untreated wood.
It's also clear that it's easy to sand through, and will, therefore be a PITA to get finished on the guitar.  But I think you're both right about a little touch of red in the clear lacquer being a Good Idea.  I'm still not sure using a brown stain might not be easier, and I won't have to deal with toxic orange crap.  I'll try that too, since I've still got more routing to do.

 

[bagman67]

Will the dichromate dissolve in alcohol?  That might alleviate the tendency for the solution to raise the grain.  On the other hand, the alcohol would be so volatile that (a) it might not allow the dichromate to be in contact with the wood in solution for long enough to do its job, and (b) dissolved chemical might also evaporate with the alcohol, and you could end up inhaling that crap.  So maybe not such a good idea.


I agree that on the scale of nasty chemicals, tinted lacquer is probably better than a chromium solution, if the cosmetic results are otherwise equal.

 

[tylereot]

Ehrm... no, I'm not going to try anything more volatile than this stuff already is.
I'm not at all convinced that this is my solution.

Next, I'm going to try similar stuff with red and brown stain, at least I don't think I need a hazmat suit with that.
I tried a 'cordovan' and a 'red mahogany' and 'brown mahogany', but there was a fair amount of purple in them.  :icon_tongue:
I think I'm also going to need a darker grain filler.

 

[Cagey]

Interesting. I didn't experiment at all - I just went for it  :icon_biggrin:

I'm surprised that it sands through that easily. I was under the impression the effect went deeper than that. But, I started into grain filling before I did any sanding, so that probably held the paper back a bit.

 

[Patrick from Davis]

The dichromate is a salt, it isn't going to go into gas phase.  Unless you find a way to make it into plasma, in which case the guitar body is probably in a lot of trouble.  Hmm, a quick look up, and the dichromate will oxidize ethanol into acetic acid.  As mentioned before, strong stuff, be very careful with it.
Patrick

 

[tylereot]

I played around with some Color Tone stains this morning, medium brown and mahogany red, on the back of the same piece of mahogany.
I think this is the direction I'm going to go.

You'll see the area on the left in the picture is more brown, area on the right more red.  This has one wash coat of lacquer over it.


I may wind up adding an amber tint to the lacquer to try to get that vintage 'glow' of the Chris Craft mahogany.

 

[Cagey]

I like the dyes better, too. Makes for a really sharp piece of scrap. Imagine what it'll do for your fiddle!

Now, square that piece up and continue finishing it, screw some hooks into it and make a key hanger to hang by the door.