Ferric Nitrate Mix experience

[Jerry V Lape]

Looking for guidance on using ferric nitrate crystals for stain.  What solvent have you used successfully and some guidance on portions of crystal/salts in solvent quantities. 

[smart dog]

Hi Jerry,
Ferric nitrate will dissolve in alcohol to make a less grain raising stain and in water.  I use water because alcohol dries too fast for my taste.  A good place to start is 5 parts water to 1 part ferric nitrate by volume.  Let me emphasize that as a good place to start but I strongly urge you to test on scrap wood.  I varied that a lot depending on the wood and my objectives.  Theoretically, ferric nitrate does not need to be neutralized with a base after blushing.  However, I wipe the stock with ammonia or brush on water and baking soda just to be sure.  You can use other stains on top of ferric nitrate to modify the color just as you can with iron dissolved in nitric acid.  You can also use tannic acid before applying ferric nitrate to darken the figure if you desire. 

dave

[D. Taylor Sapergia]

I concur with Dave's recommendations, and use similar technique.

[Jerry V Lape]

Dave
Thank you for the guidance.  I am planning on applying tannic acid first and have the test strips of the wood ready to also try several stains if the results of tannic and ferric aren't quite what I would like.  In the past I used a commercial aquafortis  successfully but want to try the ferric nitrate and tannic acid on this rifle.  Good to know the alcohol base is so quick drying.  Water is what I will try.  I don't mind the extra rub to de-whisker. 

[smart dog]

Hi Jerry,
A couple of tips I learned from experiment.  The tannic acid really works but I don't really like the dark color it gives the curl.  To my taste, it is often almost black and monochromatic.  An alternative that I often like better is to brew really strong black tea and paint the stock with that.  It adds a bit of tannic acid to the wood but more subtly and highlights curl without turning it black.  Also, if you wipe the stock with a solution containing lye as a precaution for neutralizing any remaining acid, you get the added benefit of a slightly redder color.  The photos below show a stock wet with water after blushing ferric nitrate.  The second shows the same stock painted with tea and ferric nitrate before blushing and then wet with water after blushing.  As you can see, the effect of the tea is significant.  The last photos are the finished musket.  The stock had curl but it was vague and I used the tea to bring it out.

dave

[Mad Monk]

Hi Jerry,
Ferric nitrate will dissolve in alcohol to make a less grain raising stain and in water.  I use water because alcohol dries too fast for my taste.  A good place to start is 5 parts water to 1 part ferric nitrate by volume.  Let me emphasize that as a good place to start but I strongly urge you to test on scrap wood.  I varied that a lot depending on the wood and my objectives.  Theoretically, ferric nitrate does not need to be neutralized with a base after blushing.  However, I wipe the stock with ammonia or brush on water and baking soda just to be sure.  You can use other stains on top of ferric nitrate to modify the color just as you can with iron dissolved in nitric acid.  You can also use tannic acid before applying ferric nitrate to darken the figure if you desire. 

dave

Dave,
When I first started working with the ferric nitrate solution I made from old iron and nitric acid I used baking soda to convert the ferric nitrate on the wood to ferric oxide with baking soda.  But all of the foaming it created lifted iron stain off the wood.  Mainly where the stain was light on the wood grain running parallel to the surface.  You get little stain penetration on the grain.  When I had first looked into this stain I was working with some writings of Cal Hetrick where he is explaining what he aw with a guy he called the last Bedford County gunsmith.  That gunsmith swabbed the stain onto the wood and then held the stock over is forge fire to heat the stock. When you heat the surface of the wood to about 150 F the ferric nitrate breaks down to form various colors of ferric nitrate.  If the  reaction between the nitric acid and iron is run to the end you have no live nitric acid left.  But when you heat the wood to do the ferric nitrate conversion to forms of ferric  oxide you are driving lower oxides on nitrogen out of and off the wood.  There is no nitric acid involved at this point.  Another way of dealing with it is to simply stand the stained stock in a corner.  In my basement I have a damp corner in the back of the basement.  In about a day the ferric nitrate will break down into ferric oxide.  At a certain "dampness" in the corner I got stock with black curl and more yellow and orange in the stain colors.  If you use heat, as the old gunsmith did you get mainly brown colors.

I had also used ferric nitrate crystals out of the lab chem supply.  They worked but I did not get the colors I got with the Ferric nitrate solution I made from nitric acid and old iron.  Ferric oxides come in a range of colors depending on the amount of water they carry.  Iron oxide pigments may have from no molecules of water attached to 8 molecules of water attached.  That is why you can change iron oxide colors by driving off water by gentle heating.    When up around 8 molecules per molecule of iron oxide the color is a bright yellow.  As you drive water off the iron oxide it will change to an orange color them to various brown colors and finally with no water attached you get into the reds.

This nitrate of iron stain is so variable in colors produced cabinet makers hated it.  So it was mainly seen in antiques except where you were working with one piece of wood and why the old original guns varied so much in stain color results.   In the 1600s in England curly maple was the rage for a number of things.  Getting all of the wood pieces to match was a real skill.  I should point out that nitric acid as produced in large quantities in England in the 1500s.  Also in Germany.  Acid producers were some of the first manufacturing businesses established in Philadelphia after William Penn founded the colony.

[heinz]

Bill, thanks for the detailed post.  I had searched in vain for nitric acid producers in the colonies and you found them. I do not like the nitric acid technique because I find over years it keeps getting darker, particularly with period-appropriate finishes.

[Mad Monk]

Bill, thanks for the detailed post.  I had searched in vain for nitric acid producers in the colonies and you found them. I do not like the nitric acid technique because I find over years it keeps getting darker, particularly with period-appropriate finishes.

With the ferric nitrate made with old iron and nitric acid you can control how light or how dark you want the stock by varying the strength of the stain solution.  I was doing Rev War period stocks and from what I saw in Dixon's collection they were usually rathr dark colors.  But as you got into the stocks from the 1800s they became a good bit lighter in stain colors.  It looked almost as if it were a trend in what the customers wanted.

Nitric acid production in large quantities goes back before the 1500s in Europe.  If you look at Agricola's De re Metallica you see a very detailed description on the making of nitric acid.  Then it's main use at that time of separating silver out of sulfide lead ores.  And even how to recover the nitric acid after using it to extract the silver from the lead ore.   These mineral pigment dyes from chemicals like ferric nitrate or iron nitrate were used extensively in fabric and leather dying.  We see in the early 1800s nitric acid being sold in general stores in Bedford County to gunsmiths.  Sold by the pound.

The manufacture of nitric acid in volumes in London in the mid 1500s resulted in the first document air pollution restriction.  The then King of England telling the acid companies to stop fouling the air of the city or move out of the city.  And his EPA inspector probably carried a large axe to deal with those who ignored the King's order.  No slap on the hand and a light fine !!!!

[smart dog]

Hi,
Production and use of nitric acid goes back at least to 1200 AD.  It's use as a stain was described by Theophilus in his book "On Divers Arts" published about 1200.  It was used alone to produce yellow and orange colors and then of course with dissolved iron.  An interesting detail is that much of what was learned about finishing and coloring wood came from painters, not carpenters or furniture makers.  Painters used a variety of media for their canvasses and needed preservative coatings.  That is why linseed oil and boiled linseed oil came to be used as finishes.

dave

[Ric Carter]

I did some testing with it, and went as far as 10 parts alcohol to one part ferric nitrate. Even at that dilution, it worked well. Make your own test piece.