Advocatus Diaboli

Question for chemists: KOH as part of wood treatment?

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As part of my treatment for coloring the wood, I use a 3% solution of KOH alternating with Ferric Nitrate.  I had been told by a chemist friend that it shouldn't do any damage to the wood, but recently I was talking to another chemist who thought it could cause some longterm issues.  Thoughts anyone?

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IMHO, anyone who has to ask questions like this shouldn't be fiddling with anything stronger than baking soda and vinegar until they're better enlightened.  BTW, a 3% solution of potassium hydroxide meets the definition for corrosive rather than merely irritating, and ferric nitrate is a powerful oxidizer.  Here's some basic knowledge:

 

https://en.wikipedia.org/wiki/Potassium_hydroxide

https://en.wikipedia.org/wiki/Iron(III)_nitrate

https://en.wikipedia.org/wiki/Base_(chemistry)

https://en.wikipedia.org/wiki/Acid

https://en.wikipedia.org/wiki/Oxidizing_agent

 

Now, study the question for yourself, and, as always, choose wisely.   :)

 

BTW, asking specific questions of professional friends grabbed at random can be misleading.  Chemists, like doctors, lawyers, engineers, geologists, and luthiers specialize at the working professional level.  Like ask a guitar dude about french polishing your violin, then ask somebody here.........  :lol:   

 

Synthesizing polymaths and real generalists are rare, and normally drift into some odd interdisciplinary thing or other (project management, "intelligence", systems analysis, unconventional warfare, writing sci-fi, organized crime.......), change careers serially, or whatnot.  We are blessed to have an unusual number of them running loose on MN.

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I'm not a chemist, but the rule I use for my own work is to avoid using strong oxidizers, strong acids or bases, and products which are highly hygroscopic (or tend to increase moisture absorption from the air), A lot of this comes from talking to, or reading what has been written by wood technology people (such as Bruce Hoadley), and people in the preservation business (such as museum conservators).

So neither KOH or Ferric Nitrate sound good to me.

 

We have a long history showing that plain-ol' wood is pretty stable stuff, as long as the moisture content doesn't get too high.

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David, I wouldn't consider using either of these independently.  I was told that using them together caused them to bind and essentially precipitate an iron oxide pigment into the surface of the wood.

Why ,for colour or?

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As part of my treatment for coloring the wood, I use a 3% solution of KOH alternating with Ferric Nitrate.  I had been told by a chemist friend that it shouldn't do any damage to the wood, but recently I was talking to another chemist who thought it could cause some longterm issues.  Thoughts anyone?

 

David, I wouldn't consider using either of these independently.  I was told that using them together caused them to bind and essentially precipitate an iron oxide pigment into the surface of the wood.

 

It's the word "alternating" that caught my eye here.  Implies that you are brushing on solutions of first KOH, then Fe(NO3)3, which is going to let unneutralized reagent get at and into the wood.  Also remember that the ions dissociate in solution, and that small amounts of nitric acid will unavoidably form, along with potassium nitrate that will be left behind.  If any Fe(NO3)3 is inadvertently left behind, the stuff is hygroscopic as well as chemically obnoxious.  Washing the surface (and/or treating it with lower activity acids and bases) to remove unreacted reagents and by-products, as would be done after an etching operation to ensure that it's stopped, will remove your precipitate as well.  Wouldn't just using a fine suspension of rust in water do a safer job for you? :)     

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As part of my treatment for coloring the wood, I use a 3% solution of KOH alternating with Ferric Nitrate.  I had been told by a chemist friend that it shouldn't do any damage to the wood, but recently I was talking to another chemist who thought it could cause some longterm issues.  Thoughts anyone?

I have had good success with oldwood1700.com and their ground.

Placing it in the U.V. box produces a real nice color.

 

 

 

http://postimg.org/image/fn7oy1k0r/

 

post-25139-0-18505300-1453825642_thumb.jpg

 

 

I am not a chemist, but I do not have to be one.

 

I will be probably be trying Joe's varnish on top as a student here has said some nice things about Joe's varnish.

 

http://www.violinvarnish.com/

 

A few of the other students here are using OldWood1700 and so that is why my test sample is from OldWood1700.

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AD,

When we use these "wet chemistry" reactions on the wood surface we can be reasonably sure of the initial outcome...but we have no picture of the long term as we do not know when or if the reactions are completed.  Neutralizing the surface only neutralizes the surface.  I have seen many instruments survive and thrive after such treatments and I have seen instruments that will allow you to adjust the sound post from the outside after as little as 5 years.  Perhaps you are comfortable with the risk.  I agree with David that the risk is unnecessary and therefore ill advised. 

If the issue is wood color there are many safe approaches to this issue. 

One thing I have observed many times is that the reflective results of chemically treated woods are not the same as we see in untreated wood or old instruments.

on we go,

Joe

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The attached indicates the final coloring product is ferric hydroxide, rust. What by products remain would have to be considered.

 

post-24779-0-15115900-1453846440_thumb.jpg

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I think Devil's Advocate has a very clever idea. There are ways to ensure that no (little) residual reactants remain. Absorbent paper to blot up some residuals is a start. If the iron nitrate is fully converted to rust, perhaps a mild vinegar solution will mop up the remaining KOH. 

 

Give it a shot.

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I agree with the first chemist. You should be safe. The reaction products are insoluble brown ferric hydroxide (not rust, which is ferric oxide) and potassium nitrate (which some people here apply for color), both in small amounts. The greatest danger would be from an excess of KOH, which will attack the lignin in the wood. But you aren't dealing with such quantities. I have no opinion on the appropriateness of the treatment.

 

Lyle Reedy

Retired cellophane/pulp/paper chemist

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Avoid getting KOH in concentrations mentioned on your skin,

or heaven forbid, in eyes. Hence, rubber gloves and splash

goggles are strongly recommended.

It seems there ought to be alternatives to

using the wood surface as reaction vessel.

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Lyle Reedy

Retired cellophane/pulp/paper chemist

As a paper chemist, does anything come to mind which would darken the wood uniformly (not "burn" the end grain and summer growth on the top), not attack the wood much, and leave a residue which completely stops reacting with the wood? And also doesn't leave any hygroscopic "salt" residues?

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captain hook- read the attatched- this is number two

 

Rust is not so simple its a mixture of various forms,mainly whats called  `hydrated ferric oxide` and `hydroxide-oxides`. :)

Thanks, but let's save the geochemistry of the iron minerals for other threads on other forums. It's mildly complicated.  I figured saying "rust" was good enough for the current purpose.  I was just hoping here to help someone avoid ruining their fiddles or burning themselves, and maybe get them to read a little chemistry in self-defense.  :)

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As a paper chemist, does anything come to mind which would darken the wood uniformly (not "burn" the end grain and summer growth on the top), not attack the wood much, and leave a residue which completely stops reacting with the wood? And also doesn't leave any hygroscopic "salt" residues?

Ammonia fumes work for me. No residue at all. It does tend to darken the winter growth a little more than summer. Soaking in household ammonia can make wood brittle and the color may not be what you want.

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Ammonia fumes work for me. No residue at all. It does tend to darken the winter growth a little more than summer. Soaking in household ammonia can make wood brittle and the color may not be what you want.

Yup.  As described in several other threads, it gives one a nice excuse to raise rabbits, as well.  :)

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I've experimented with this process as well. The results are lovely. I too have wondered about long term effects, but then I thought that this is basically the same process people have used to "set" the blacks of their purfling while dyeing. Wouldn't we know, through trail and error, any negative long term effects? 

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If you want to see where the color comes from add some ammonia to crushed rosin. I have samples (crushed rosin) over 20 years and have shown no change. I'm pretty sure any rosin that fell into the pee bucket also got the same treatment. Urine in contact with any organic substance will develop ammonia.

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If you want to see where the color comes from add some ammonia to crushed rosin. I have samples (crushed rosin) over 20 years and have shown no change. I'm pretty sure any rosin that fell into the pee bucket also got the same treatment. Urine in contact with any organic substance will develop ammonia.

 

Have you never tried it for making varnish?

Well, I should ask first: what color is this rosin reacted with ammonia?

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