Vinegar and Iron

[pflyman]

I am practicing techniques for an upcoming build of Don Stith's 1792 Contract Rifle.  While I have Aqua Fortis (Wahkon Bay), I was intrigued with a past thread on the use of vinegar and iron.  I created a batch with 5% cider vinegar and 0000 steel wool (I added heat to perhaps speed the action).  It appears that some builders use and are pleased with this approach, but I would like to hear from those that have what techniques, secrets, successes or failures they may have encountered.  Is heat necessary to react it?  If necessary, is the heat applied after the solution has dried or is still wet?

[Acer Saccharum]

commercial steel wood has oil on it. It's good to wash it in detergent and hot water, then clear rinse several times before using.

Long John got me started using vinegar stain, and I am very fond of it. It's an acid which carries iron molecules into the wood. Same thing that aqua fortis does, but with no toxicity issues. I use it to stain maple, leather, pine, poplar, etc. Beautiful. Takes a while to brew, though.

I never had to heat the wood afterwards to bring out the color.

Acer

here's my photobucket album with colors: http://s12.photobucket.com/albums/a246/Tom45-70/Vinegar%20stains/

[t.caster]

Acer, do you use cider or white vinegar? Full strength or water diluted?

[Long John]

Pflyman,

You have already made it harder than it need be.  Just drop some old barbed wire into a bottle of cider vinegar and come back in a week or two.  No need to heat!  As a matter of fact, since acetic acid has such a high vapor pressure heating drives acetic acid out of the solution so there is less to react with the iron.

If you have an excess of iron for the acetic acid in the vinegar you will get a solution that is mainly ferrous acetate which will yield brownish black color when applied to the wood.  If you have excess acid for the iron in the solution you will get a solution that is predominately ferric acetate which will yield a reddish brown color when applied to the wood.  With a weak acid for your acid/iron stain you get to choose.

When you put the iron into the vinegar you get a solution of ferrous acetate and ferric acetate.  When this solution is applied to the wood and the water begins to evaporate the acetic acid evaporates right along with it.  The evaporation of the acetate leaves the iron ions, ferrous and ferric, all alone and they snag onto oxygen from the air turning into either ferrrous oxide (brownish black) or a mixture of ferric oxide (reddish orange) and ferrosoferric oxide (reddish brown) in the wood.  No heat is necessary!  When the stock stops smelling like salad dressing the vinegar is gone and the reaction is complete.  This is the only respect where acetic acid from vinegar differs from nitric acid.  Nitric acid must be heated to get it to evaporate from the wood, acetic acid does not.  The oxides of iron left in the wood are exactly the same, whether they were obtained using vinegar or nitric acid.  

This rifle was stained with vinegar iron stain.


I took a small quantity of my stain solution from the masonry crock I store it in and mixed it 50/50 with vinegar.  That "pushed" the chemical equilibrium between ferrous and ferric acetate towards the ferric acetate end to give me a redder final color.  If I had not added the vinegar the stock would have turned out much browner.  I applied 3 coats of stain, allowing the stock to dry and then rubbing down with steel wool between coats.  Essentially, I de-whiskered and stained at the same time.  The final finish is tung oil.

Best Regards,

John Cholin

[Acer Saccharum]

I used cider vinegar, straight from the supermarket.

Iron filings.

Time.

The stuff stinks when it's brewing, by the way. You might get some dirty looks if you brew it in your kitchen.

[FG1]

I tried it using degreasd steel wool and white vinegar( that was in pantry) instead of cider vinegar and the results were a black and gray appearance on cm ? Any ideas why ?

[BobT]

I just mixed up my first batch of vinegar stain the other day using about a cup and a half of white vinegar and a handful of nails. I applied it to a white pine powder horn end cap I'm making. It turned out a "muddy" brown color, not bad but not exactly what I was after. I plan to experiment with more/less iron and different vinegar.

Not to steal the thread but what is the shelf life of this stuff?

[Ephraim]

I use it all the time cyder viniger and old cut nails or barbed wire work best it is a good old time stain .
Ephraim

[Acer Saccharum]

I have never had highly predictable results with the vinegar stain. the color you get is often a reaction between the wood and the stain. Put the same stain on maple from different trees is going to yield different results.

This stain really needs to sit on the shelf and cook for a long time. Get yourself a batch going, and then let six months go by. Age seems to improve it. Add vinegar when needed.

Acer




Notes from John Cholin, from the old ALR:
For those of you curious about cider vinegar/iron nails stain I have posted on the topic a couple of times. I don't know if those posts were saved or tossed.
About 20-some years ago I read, some where I wish I kept the article, that the old timers stained stocks with a mixture of cider vinegar and iron nails. I was building my first rifle at that time so I took a jug of apple cider that had gotten "randy" tossed in some nails and let it work. Ever since then that has been my stain.
When you make aqua fortis/iron stain what you are really doing is making iron nitrate with some excess acid. Nitric acid has a very low vapor pressure at room temperature so it does not evaporate from the wood very fast. Once in the stock the iron nitrate gives up the iron ion to oxygen in the air which becomes one of the 3 iron oxides (ferric oxide, FeO3, ferrous oxide, FeO or ferrosoferic oxide fe3O4iron oxide). Heating the stock accellerates these reactions. The nitrate ion bonds with a hydrogen in the wood and has to evaporate or be neutralized and washed away.
You can make the iron oxide with acetic acid too! Acetic acid is a weaker acid than nitric so you have to give it more time to combine with the iron and turn the iron into iron ions that are in solution as iron acetate. The nice thing about acetic acid is that you can drink it or sprinkle it on your salad with out much adeiu. It also has a much higher vapor pressure so it evaporates out of the wood quite quickly. If the stock does not smell like salad the acid is gone and all of the iron ions have become iron oxide. Thus there is no need to neutralize unless you can't wait another hour.
Ferrous oxide, FeO, is black to blackish brown. Ferric oxide, Fe2O3, is orange to red to readish brown. Ferrosferic oxide, Fe3O4, is brown. With the iron acetate (cider vinegar/iron nails) stain you can modify the color by changing the relative concentrations of the acid and the iron. Like blackish brown stain? Put in excess iron into the pot, wait a couple of weeks had use it just like any water based stain. Like a redder stain? Put in excess vinegar, wait a couple of weeks and use like any other water-based stain.
I use the stain to raise the grain on my rifles. Each rifle gets 3 or 4 applications of stain, followed by a good rub down with OOOO steel wood. On the carving I use a brush made from hemp rope to burnish the stock wood.
5 years ago I built my 54. On that rifle I had a pretty even balance and it came out reddish brown. On my nephew's rifle he wanted more of a walnut color so I added iron to the pot. By the time his rifle was ready for staining it was turning the wood a nice chocolate brown. On my brother's rifle he wanted a redder stain so I added vinegar to the pot and by the time his rifle stock was ready to stain the stain was turning maple wood a nice reddish brown. Paul's rifle was in there too. He liked a dark stain so he got extra iron. Now that I am building another one for my self I will add a little iron to brown it some from what I had for my brother's rifle.
Since modern nails are often made from manganese steel, these days I hve started getting my iron from old barbed wire that I find up on the farm.
I have been using the same pot of stain ever since I built my first rifle over 20 years ago. (I built a couple disasters quit for 15 years and have now gotten back into it.) A couple of the kids' guns were stained with commercial stain. I didn't like the way they came out but the kids don't care - it goes bang and makes lot's of smoke. But on the adult rifles, for family and friends, I use the cider vinegar and iron stain. Besides, all of the old time gunmakers had plenty of vinegar at their dispoal, they did not have to have it shipped in from England.
I hope this answers your questions. And yes, I was a chemistry major in college.
If your mixture has just turned a dull gray it could be because of alloying elements other than iron. I started with rusty nails from an old barn. Now i am using bits of old barbed wire for iron. It could also just need more acid (vinegar). My pot of stain has been brewing for over 20 years! I end up adding vinegar or hard, sour cider every so often to make up for evaporation. It looks like coffee. You could also add some hydrogen peroxide (H2O2) solution, obtained from the pharmacy. Hydrogen peroxide is know as a bleaching agent because it oxidizes pigments, changing their color. When iron is exposed to hydrogen peroxide solution the H2O2 breaks down to H2O and O, free oxygen. that free oxygen should combine with the iron to produce iron oxide. But iron oxide is not very soluble in water. The ferric ion needs a cation like the nitrate or the acetate to keep it in solution. When the solution of iron ions is applied to the wood and the solution dries, the positively charged ferric ions are left with out a negatively charged nitrate or acetate and combines with atmospheric oxygen during the drying process. The key is in finding a negative ion that keeps the iron in solution but leaves once the stain is aplied. the acetate works well because of its high vapor pressure at room temperature.
Yes there is a bit of a difference between white vinegar and cider vinegar in that white vinegar is distilled, I think over mineral oil but I'm not sure, to refine out the compounds responsible for the tan color. As long as the acetic acid contents are the same the chemical properties will be the same. when I have to add vinegar to my pot of stain I go into the kitchen and get what ever is in the cupboard. If you REALLY like a red color you could probably use wine vinegar but the wood might turn out purple!
Ferric nitrate mixed with dilute acetic acid (vinegar) would probably produce a similar solution but I have never tried it.
Over the next couple of days I will try my hand at posting some pictures at theat photobucket site so you can see what I get with an iron/vinegar stain.
Best Regards,
John Cholin

[Roger Fisher]

Well now, looks as if I have to cart the wire cutters along hunting or stay with my mix of Jimmy Chamber's stains.

[cal.43]

Vinegarstain on cheap maple, the stain was made from concentrated vinegar and steelwool

[pflyman]

Great information!  I even got a refresher on chemistry - most of which disappeared from my "hard drive" years ago.  Acer is right.  The mixture does stink.  After I heated it last night, my wife brought that to my attention.  I have an old pistol kit that has remained unfinished for perhaps 20 years or more.  Initial prep of the maple suggests that it might have some nice figure.  No harm in trying with this piece.  I will report back with my results.  Thank you all.

[Dphariss]

I am practicing techniques for an upcoming build of Don Stith's 1792 Contract Rifle.  While I have Aqua Fortis (Wahkon Bay), I was intrigued with a past thread on the use of vinegar and iron.  I created a batch with 5% cider vinegar and 0000 steel wool (I added heat to perhaps speed the action).  It appears that some builders use and are pleased with this approach, but I would like to hear from those that have what techniques, secrets, successes or failures they may have encountered.  Is heat necessary to react it?  If necessary, is the heat applied after the solution has dried or is still wet?

Just be aware that vinegar and iron does not stain wood in the way that Nitrate of Iron (AF) does since vinegar will not dissolve as much iron. Thus it may require repeated applications to get the color desired. AF will stain maple in one coat, less "water" put on the stock is better.
I assume that if there is a sludge in the bottom of the container used to make the vinegar stain that this might give better color. But its not the same process as using nitric acid to dissolve the iron. Note also that wine vinegar is 8% cider is generally 4% acid. Compared to nitric cut 50% with water it is very very weak and will not "eat" as much iron. Thus the nitric acid will produce a stain with far more iron in solution and better color. I think the time required to make the stuff and the low iron content are probably why vinegar and iron was not used for gunstocks. It was apparently used as a tint in furniture building according to my source.
If the store bought AF you have is made to the old formula it has hydrochloric acid added and this tends to muddy the grain and produce a browner stock over the long term. At least for me.

I let the stain dry completely or nearly so. Wet wood is harder to heat. Use radiant heat.

I have never tried my home brewed AF on pine but it works great on oak.

Dan

[Acer Saccharum]

pflyman, give your stain mix plenty of time to dissolve and stop reacting before you put it to use on the real thing.

Acer

[Blacktail]

Vinegar stain again, awesome! I made some up with degreased steel wool and cider vinegar. The liquid is dark, reddish brown, but when I apply it to maple, it comes out a nasty bluish-gray color. Any ideas why?

[Acer Saccharum]

I suspect one of the following:
a) your batch hasn't spent enough time brewing
b) you need more applications of the solution( I found up to four apps works best)
c) there is not enough acetic acid in the batch(add more vinegar)

For additional color variation, try a wipe with DILUTE Hydrogen peroxide. This may turn a dark stain reddish, or even rusty orange.

This gun is vinegar stain, with a peroxide wash:

[pflyman]

Well...I have made two applications of the vinegar/ steel wool brew.   The concoction is a dark coffee color in the jar, but I must admit, I jumped the gun rather than give it the time to "brew" as has been recommended.  It went on light brown but it turned grey.  It is not what I had hoped for, but the gist of this thread has been not to expect a certain color.  The good news is that, when rubbed down with steel wool, the result is surprising definition of the figure in the wood which was not evident in the untreated piece.  I would have preferred red-brown, but the result when finished may be attractive.  I am not deterred.  My next try will probably include old barbed wire (there is plenty of that in S Dakota) and more patience.

Dave

[Long John]

pfly,

The gray color is ferrous oxide.  If you have ferrous oxide that means that there is more iron in your solution than there is acidity so the iron has to compete for acetates.  Under those conditions the iron only gives up 2 electrons and the resulting oxide is gray.  Pour your stain solution  ONLY into a clean jar.  Add fresh vinegar to it until you have twice the volume of liquid.  Put a lid on the jar and let it sit for a few days. NO HEATING!  Then try the new stain on a fresh test block.  And, yes, I usually apply several coats allowing the stain to dry between as mentioned above.

If you are really impatient rub the gray wood with a little dilute hydrogen peroxide. You will get the same effect but quicker.

Best Regards,

John Cholin

[Karl Kunkel]

This thread is great.  How much iron do you need to add to a bottle of vinegar (how many nails)? About how long are we talking for the stain mixture to brew? Sounds intriguing.

[Woodbutcher]

The colors that I see on those rifles are incredible!
  OK, so I get a quart bottle of cheap white vineger. And some steel wool. I'll wash the steel wool and rinse it well, and then rinse it in alcohol, to degrease it.
 (1) How or where does one get concentrated vinegar? Would it help?
 (2) How long is enough time to brew? 2 weeks or more enough?
 (3) Does rust matter, or should it be brushed off?
 (4) It smells bad, so does that mean that you leave the lid off?  If the lid is kept on tight would there be a problem when it's opened? H-mmmmmm!?!!
 (5) Would it be good to pour the vinegar into a larger container, perhaps a quart poured into a glass gallon jug.
 (6) With winter coming this will need to be kept from freezing, so outside won't work. This "smells bad" thing could be a problem, even in a cool basement! A fella could get shot and have the thing buried with him! Any suggestions about dealing with the "smells bad" would be helpful.
 (7) I see mention of a dilute hydrogen peroxide wash. About how much water, maybe half and half?
  Testing the finished brew on scrap wood and adding fresh vineger to get the desired color seems clear enough. It will be interesting to see the effect on other types of wood. Thank you.  Woodbutcher
 
 

[Seven]

woodbutcher,  I don't think it smells all that bad.  It smells mostly like, well, vinegar.  I used to keep a quart jar of it brewing on a shelf in my work room and the only time I really noticed it was when I was doing things right next to that shelf.  I use cider vinegar as that is what was recommended on the first thread of vinegar stain making from the 'old board'.  I haven't used white vinegar so I have no comparison.   Once I got my stain to the point of looking good on wood I put the cap on the jar and now I don't smell it at all.  I started with steel wool and then I made another batch with some old rusty nails.   I let my original batch sit for six months.  I've let other batchs since then sit for much shorter (a month or so).

I did use the hydrogen peroxide trick before I had gotten my stain figured out.  For that I just used a cotton ball.  Placed it on top of the bottle and tipped the bottle over wetting the cotton ball.  Then squeezed out the cotton ball over the sink until I got as much out as I could.  Then used that to wipe on to the wood.  The result is immediate.  Second and third wiping of Hydrogen peroxide didn't do anything, so I'd have to assume that the reaction from the first wiping was enough to make it complete.

I have not used this stain on a stock yet, but I have used it on a fair number of scraps around the shop.  It really brings out the curl and in my opinion looks great.  The part I love about this stain is that I made it and it is very easy.  Don't over think the process.  Listen to Long John's post (two or three above this one).  And have some patience when brewing up a batch. 
-Chad

[Acer Saccharum]

Bad smell: interpret as smells like @$#%. This only is very noticeable in the first few days of brewing. DON"T screw the cap on tight, as the gas buildup could conceivably blow up the jar. Then you have a real problem. To speed brewing, I screw the cap tight, shake the bottle, then back off on the cap to allow gas to escape. Always back the cap off. This stuff keeps outgassing for months.

In my experience:
A note on the hydrogen peroxide: if your stain is too dark, and you choose to use peroxide to change the color, go very cautiously into the application. The change in color is usually immediate and dramatic. Further applications of vinegar stain have very little effect on peroxide treated wood.

Acer

[Woodbutcher]

 Thank you gentlemen, all of you. I'll be getting a bottle of apple cider vinegar this afternoon and starting my own brew.   Woodbutcher

[BobT]

This would be a good thread for the tutorials!

[Elnathan]

Does the metal involved in making this stain have to be real iron or can one use steel? I think I recall reading on previous threads that it had to be iron, not steel, but that aspect doesn't seem to have been brought up thus far. I have never really had any access to wrought iron in significant quantities, so I have never tried to make vinager stain - if I can use mild steel, that makes it a lot more practical endeavor.