nitric acid

[RichG]

when using nitric acid based solutions to darken wood, does leaving it on longer before applying heat help to darken the final color? how long could you possibly leave it? how about the amount of solution swabbed on? I would think after a period of time the acid would be used up. a couple of hours, a day? 

[bob in the woods]

The acid is "used up" prior to the application. Iron dissolved in the acid is what gives the colour. I'm not sure what effect you would get with the application of just nitric acid, since I've never tried it.

[Acer Saccharum]

I think the heat causes any remaining nitric to evaporate. Nitric has a higher vapor pressure, and needs heat to complete the evaporation. That's my limited understanding. Vinegar stain contains acetic acid, which evaporates without the use of heat.

Both acid based stains carry iron into the wood, where it bonds with the wood.

[rich pierce]

The acid is "used up" prior to the application. Iron dissolved in the acid is what gives the colour. I'm not sure what effect you would get with the application of just nitric acid, since I've never tried it.

Nitric alone does very little to maple.  It's the iron oxides that lend color.  Maybe nitric acid alone would stain ironwood pretty good.

[Dphariss]

when using nitric acid based solutions to darken wood, does leaving it on longer before applying heat help to darken the final color? how long could you possibly leave it? how about the amount of solution swabbed on? I would think after a period of time the acid would be used up. a couple of hours, a day? 

If the stain is very acidic and/or its adulterated with Hydrochloric leaving it on and not neutralizing will likely turn curly maple a uniform muddy brown with no curl showing (more likely with the Hydrochloric mix I think).
So use nitrate of iron unadulterated, either made from dilute nitric acid depleted with iron or from Ferric Nitrate crystals.
Put in on heavily and uniformly allow to dry. Blush with RADIANT heat using care to not burn corners and carving. Neutralize if needed or finish with a natural oil/oil varnish that has been acid neutralized in its making. I neutralize then finish.
If its done properly the rifle can be stained in the morning and hunted with in the afternoon or the next morning.
Wood is wood. It ALL reacts to stain differently and care must the used and some experience helps. Some stocks will not take the stain uniformly and may need to be allowed to dry then the areas that show no color restained the next AM.
Worrying about the color? Most rifles were stained with nitric then finished with a linseed oil varnish of some sort. Whey people demand the wood conform to some color they have preconceived. I don't bother with this. If the stock is finished in the manner described it will be "right" for what the wood wants to be. Just like it would have been if done by JP Beck or John Armstrong. Some rifles may need a colored varnish to be "right" if one is that finicky.

Dan

[James Rogers]

The acid is "used up" prior to the application. Iron dissolved in the acid is what gives the colour. I'm not sure what effect you would get with the application of just nitric acid, since I've never tried it.

Nitric alone does very little to maple.  It's the iron oxides that lend color.  Maybe nitric acid alone would stain ironwood pretty good.

I dunno Rich. I have seen some lovely maple pieces colored with water/nitric mix at 5:1. I have also used this myself to very good effect.

Here are a few done this way. The bottom three rifles were done with the above mix with nitric only. None were neutralized after application and all three are purt near exact color after 20-30 years being done.

[WadePatton]

when using nitric acid based solutions to darken wood, does leaving it on longer before applying heat help to darken the final color? ...

That Q has been answered i reckon, but I think "darkening the final color" hasn't been addressed.

I have found in my very limited experimenting that it takes two or three applications, blushed each to get close to the darkness i want.  Also that the heat source matters. 

Every piece of wood is different (assuming from different trees) in how it responds to these types of staining processes.  Experimentation on scraps from your work will give best approximation.  The old hands, from what i've read, tend to just let it happen and take whatever color they get. 

(similar but diff't) I'm using nitric/iron on this one (because i have some), but have learned to prefer acetic acid/iron acetate-as i can make it, it is non-toxic, blushing with heat is unnecessary and i can vary the color somewhat.  see: http://americanlongrifles.org/forum/index.php?topic=28345.0

[Dphariss]

The acid is "used up" prior to the application. Iron dissolved in the acid is what gives the colour. I'm not sure what effect you would get with the application of just nitric acid, since I've never tried it.

Nitric alone does very little to maple.  It's the iron oxides that lend color.  Maybe nitric acid alone would stain ironwood pretty good.

I dunno Rich. I have seen some lovely maple pieces colored with water/nitric mix at 5:1. I have also used this myself to very good effect.

Here are a few done this way. The bottom three rifles were done with the above mix with nitric only. None were neutralized after application and all three are purt near exact color after 20-30 years being done.

I playing around with stain I made a batch that did not really give color. It was completely depleted near as I could tell. I added just a little acid and the color came on. ?
Our guild president made some from the crystals and it looked just like the same wood stained with stuff he made from acid. So does acidic stain work better? In one case it seemed to?
All my stain is acidic to some degree. And will react when neutralized after its blushed. I have also neutralized before heating and this pretty much destroys all the color and makes things pretty ugly. So its not just the iron IMO.
Making sure the wood is well heated is supposed to help reduce the acidity but evaporating the acid does not make the wood neutral. The acidity endures. So I use a baking soda wash.
Dan

[RichG]

I agree with Mr. Rodgers as to the color of stocks when using plain nitric acid. The stock I used it on looks like the two lighter colored guns in his photo. you don't have to dissolve iron in the nitric to color the wood. Wade, I'll try applying and blushing multiple coats and see if my 10% nitric will darken like the nitric/Iron seems to. I know it wont be as dark, just trying to achieve a darker tone on my Lehigh.

[rich pierce]

The acid is "used up" prior to the application. Iron dissolved in the acid is what gives the colour. I'm not sure what effect you would get with the application of just nitric acid, since I've never tried it.

Nitric alone does very little to maple.  It's the iron oxides that lend color.  Maybe nitric acid alone would stain ironwood pretty good.

I dunno Rich. I have seen some lovely maple pieces colored with water/nitric mix at 5:1. I have also used this myself to very good effect.

Here are a few done this way. The bottom three rifles were done with the above mix with nitric only. None were neutralized after application and all three are purt near exact color after 20-30 years being done.

Looks really good.  I may have to try it again, James.

[WadePatton]

Just when i thought i had learned a couple of things about staining stocks...i learn a third!

 

[Dr. Tim-Boone]

Well Wade, we must not really be getting old... we are still learning!!