Avoiding that awful green stain

[Randall Steffy]

I have seen nice muzzleloaders of modern build which with time have turned a most horrid green color. Probable cause has been addressed or proposed on this forum before, however a refresher course would be appreciated. And if even one such incident, suprise outcome, can be avoided it would be well worth the time writing a post. At least it seems so to me. It sticks in my head that chromium trioxide may be one culprit, but read somewhere that if applied post AF that the green will not happen. But who can say for sure. I like the color I get from a bottle of chromium trioxide bought from DGW some 30 years ago but will toss it out if there is even a chance of my hard work turning green as the result of something I ignorantly used or used improperly. Please give us concerned ones a heads-up if you are sure of the green problem and cause.
Thanks much.

[Roger Fisher]

The Chrom Tri is the culprit if I remember correctly.  It turns the stock in to a green machine.  Since I have never owned or used any of it I am only 99 % sure about it!

More learned folks will add to this!

[D. Taylor Sapergia]

I have seen the colour to which you refer.  And it was CrO3 that was used.  Mostly it was on rifles and guns built in Washington back in the mid seventies.  At that time, I stocked two rifles in very hard red maple, stained them with potassium permanganate and then Chromium Trioxide, and the came out a very pleasing colour.  They faded badly over the years and while the original stain shows in the creases, all that is left is a mid brown.  One I rebuilt for the fellow, and restained it with alcohol based NGR stains I was using at that time.  But neither turned green.

[Mad Monk]

I had worked with potassium permanganate in the past with curly maple deer antler mounts.  In the house, little exposure to sun, within a few years most of the color faded away.

Using chromium trioxide to stain a stock takes a risk.  Some turn bright green and some do not.

When you use chomium trioxide (chromic acid) to stain the stock you are using it to oxidize the wood.  The color of spent chromic acid is grass green.  I had used it for years in the lab to clean traces of synthetic polymers out of glassware.  We knew when the chromic acid was spent or exhausted when it turned bright green.  Once bright green we disposed of it and made up a fresh batch.
The spent chromic acid is water-soluble.  So once you finish the stock the spent chromic acid will migrate out of the wood to be trapped under the finish.  This migration is why it sometimes takes a few years for the green color to dvelop fully.

[Jim Filipski]

Mad Monk....  Hey Bill,
25 years ago I built a few guns using ferric nitrate & Neutralized Then over that  Chromium Trioxide Then Neutralized and they have been the stable deep brown all that time. No green.
Don't ask me why I came up with that combo of stains but I liked the results. Have never done that since however.
Jim

[Benedict]

I used chromium trioxide years ago.  fortunately it was on a powder horn.  it turned a greenish color.  Since that is NOT something I want on a gun, I quit using it.  Why take a chance.

Bruce

[rich pierce]

I used chromium trioxide years ago.  fortunately it was on a powder horn.  it turned a greenish color.  Since that is NOT something I want on a gun, I quit using it.  Why take a chance.

Bruce

Greenhorn.   

[Wyoming Mike]

Chromium trioxide will turn gree as the chomium oxidizes to a different state.  Depending upon the wood, it can take anywhere from one to ten years for it to happen.  Chromium trioxide does bring out the figure in the wood better than a lot of stuff but the greening problem does affect how useful it is.

The only way around it, I have found,  is to use a red stain, LMF Maple or the old BC Colonial Red, on top of the chromium trioxide.  The rifle start our as a reddish brown.  As the chromium goes green the red combines and changes the red to a rich brown.

[Kentucky Jeff]

Sometimes Aqua Fortis will turn Red Maple green when you first apply it.  Fear not.  As soon as you heat it it will turn brown. 

[Jim Filipski]

Chromium trioxide will turn gree as the chomium oxidizes to a different state.  Depending upon the wood, it can take anywhere from one to ten years for it to happen.  Chromium trioxide does bring out the figure in the wood better than a lot of stuff but the greening problem does affect how useful it is.

The only way around it, I have found,  is to use a red stain, LMF Maple or the old BC Colonial Red, on top of the chromium trioxide.  The rifle start our as a reddish brown.  As the chromium goes green the red combines and changes the red to a rich brown.

Ah! Could be why on those two earliest builds, the problem never showed up because the AF made the stock pretty red and the CrO3 buffered it down to chocolate brown. I always wondered how they escaped the "green" fate &  thought it was because the CrO3 was neutralized the same as the AF. Well that was a long time ago when first starting out. I still have one of them and see the other from time to time Both have pretty good curl. Glad they never got the "greens"

[Evil Monkey]

Chromium trioxide will turn gree as the chomium oxidizes to a different state.

So..... being from canada, if I use it, does that mean that the chromium will oxidize to a different provence??.

[Ian Pratt]

Yes.

However, when we top coat a potentially green chromium trioxide stain with a reddish stain, we eventually get a rich brown. In Canada the same treatment results in a new red green.

[Randall Steffy]

Red Green. Now there we have good Canadian humor!
Thanks for your responses guys. I am inclined to relegate the Chromium Trioxide to the seventies.

[Long John]

Friends,

I was traveling when this post first started and this is the first opportunitty I have had to reply.

Chromium trioxide is a reddish crystal.  When chromic acid stain (actually a solution of chromic oxide) is applied the solution is absorbed by the wood.  As the water evaporates the chromium trioxide (CrO₃) is left behind imparting the reddish brown color to the wood.  The problem comes from the fact that chromium also forms a compound called chromium sesquioxide, Cr₂O₃ which is green in color.  In most cases a chemical equilibrium will develop between the two forms of oxide.  A wood stock with chromic oxide in association with the cellulose can allow the transition to the sesquioxide due to the presence of the adsorbed water that is always present in the wood.  Consequently, the use of chromic oxide as a stain is a bit of a $#@*-shoot.  It can turn green on you sooner or later, a little or a lot depending mostly on the availablity of water molecules in the material to which it has been applied.

There is another reason NOT to use chromic acid or chromium trioxide - it is quite toxic and can lead to long term, irreversible neurological damage.  Iron oxides are MUCH SAFER.

Best Regards,

John Cholin

[Roger Fisher]

Friends,

I was traveling when this post first started and this is the first opportunitty I have had to reply.

Chromium trioxide is a reddish crystal.  When chromic acid stain (actually a solution of chromic oxide) is applied the solution is absorbed by the wood.  As the water evaporates the chromium trioxide (CrO₃) is left behind imparting the reddish brown color to the wood.  The problem comes from the fact that chromium also forms a compound called chromium sesquioxide, Cr₂O₃ which is green in color.  In most cases a chemical equilibrium will develop between the two forms of oxide.  A wood stock with chromic oxide in association with the cellulose can allow the transition to the sesquioxide due to the presence of the adsorbed water that is always present in the wood.  Consequently, the use of chromic oxide as a stain is a bit of a $#@*-shoot.  It can turn green on you sooner or later, a little or a lot depending mostly on the availablity of water molecules in the material to which it has been applied.

There is another reason NOT to use chromic acid or chromium trioxide - it is quite toxic and can lead to long term, irreversible neurological damage.  Iron oxides are MUCH SAFER.

Best Regards,

John Cholin [Wow!!~/quote]I'm beginning to think Barbara has been right for 60 yrs or more...I don't know what I'm talking about - she says dumb (I say uninformed!)