Darkening Aqua Fortis stain

[Cossack]

I'm a very long way from being ready to finish my rifle, but I've been thinking about finishes and experimenting a little.  I used TOTW Aqua Fortis to stain some scrap maple (not from the stock) to get a sense of how it works (surprisingly easy!) and then I stained the vise block of my precarve stock. It's pretty, but especially on the sections of maple with little figure, the effect is still very light.

I like a dark finish, and like the browns emphasized a little more than the reds:
https://www.jimkibler.net/rifle-9.html
https://www.allenmartinrifles.net/gallery-of-guns/bucks-county-gun/

I know that I'm at the mercy of the stock wood, and I also recognize that, because of inconsistent curl in my stock, I'm going to have it lighter in parts, because a lot of curl darkens the overall effect. Mine only has that in stretches.

Here are some ideas I had for more overall darkness, that I'd like your thoughts on:

1. More applications of Aqua Fortis (I did two on the pieces shown).
2. More coats of oil finish (I used 4 in the photos).
3. A different oil finish (I used boiled linseed oil on 1 scrap side and on the stock, and BC Tru-Oil on the other side of the scrap. Tru-Oil seems slightly browner and darker, but I'm not sure. I'm open to other ideas).
4. Dyes - I was hoping to avoid these, as I understand that they can fade.
5. Kibler's Nitric Acid - does it darken the whole effect, or just increase the contrast?
6. Kibler's bone black - it seems like this would increase the aged effect, like on Allen Martin's rifles.

2 applications of AF, 4 coats of BLO on both stock and scrap:


2 applications of AF, 4 coats of Tru-Oil on scrap:

[canadianml1]

Kibler's tannic acid combined with aqua fortis will definitely make the end grains darker but I would say tending to black. Bone black I regard as strictly for local application to age and add character to the gun.

I don't know how long you left the AF on before heating but leaving it longer before heating   with plenty of it on the stock will deepen the brown. Also, the stock will darken with time which tends to reduce the contrast  you see at first.

[Not English]

More applications of Aquafortis will darken it up, more heat can help as well. Track's aquafortis is not terribly strong. I make my own but it is pretty strong. The thing with too dark using aquafortis is that it can always be steel wooled back lighter. Boiled linseed oil will also darken up over time.

[borderdogs]

I will be interested to see what people suggest on this subject. I have only used AQ once a long time ago but I am almost at the stage to use it again on my present build. Like you Cossack I like the darker look too and I also like the boiled linseed oil finish as well. The last time I did an linseed oil finish I applied  it then heated it over a grill. The heat on the linseed oil as I recall helped it absorb in the wood. What I did was apply it let the stock stand overnight then heated it up the next day. I didn't heat it so hot that it was too hot to hold I just tried to radiate the heat around the stock. I really liked the finish when it was done. As I recall I only applied AQ once.
Rob

[Hungry Horse]

 Tannic acid will really get even pretty mild aquafortis to darken the end grain. Tannic acid also really works well with vinegaroon. In fact often when heating the stock after the final application, and drying time, it will turn totally black. This will scare you to death if you paid a lot of money for the blank. But, it can be rubbed back with Scotchbrite to maximum contrast.
 Getting linseed oil finishes to dry requires sunlight, not heat. Using heat is too risky IMO.

  Hungry Horse

[Chowmi]

You can also try some Laurel Mountain Forge Lancaster Maple stain after the aqua fortis.  It will darken the stock.  I overdid it once and got a stock much darker than I wanted. 
After the AF, then just use the stain in light coats until you get what you want. 

cheers,
Norm

[smallpatch]

Add LMF stains to darken the wood to your specs.  AF will only go so far on a given piece of wood.
As you can see from your piece, the figure gets dark on the end grain, Based on the chemical make up of the wood, and the tannins that are present.
If there is figure there, The AF will bring it out, but can’t bring out what’s not there.
A tannic acid bath can darken it quite a bit.

[Not English]

If you want a linseed oil finish, here's what I do. I first thin out my boiled linseed oil with mineral spirits using a 2:1 ratio of mineral spirits to oil. The ratio is not real important, the thinning of the oil is so  it can go down in the pores of the wood. I apply as much thinned oil as the stock will take working it in with my hands. Leave the stock to dry making sure there are no puddles of oil on the stock (it will plasticize and stay gummy). When dry, add another coat of oil, thinned or not, following the same procedure of rubbing it in. Your finish will probably not be too bad at this point, but I do another coat or 2 of full strength linseed oil. Keep at it until you have a finish you're happy with. The thing to remember is to let the previous coat dry before adding another. It is good to handle and rub the oil in whenever you feel like it.

[WadePatton]

Although tannic acid can be purchased in powder form from many sources, I used box red wine to add tannins to my Maple stock. It's what I had on hand and it worked just fine. Won't add any red tones but does darken the effect of the AF. 

[TommyG]

I will always test on scrap from the same blank.  I use the ferric nitrate crystals mixed with denatured alcohol.  I will try different strengths to achieve the darkness I want, i.e.- 3:1, 4:1, 5:1  - with the 3:1 being the darkest.  Also, 2 or more coats will make things darker.  I put on the coats before I heat blush.  I also use Klein's(Dangler) stains, thinned at different ratios to achieve the color/contrast I'm after.  I stick with 2 different colors - red/brown and brown.  Sometimes I use just the red brown, sometimes both.  I've never tried the tannic acid, but probably will sometime in future builds.

[smallpatch]

Forget the linseed oil.  It’s water permeable, and doesn’t dry by itself.  It’s an oil, not a varnish.  If you must use it, you’ll need to add some driers.

[Hungry Horse]

Linseed oil alone is but half of the original recipe. Boiled linseed oil, thinned with turpentine, some japan drier, and some melted bees wax, applied in light coats, and rubbed in by hand, is a reasonably serviceable finish.

  Hungry Horse

[Mike Brooks]

When I use TOTW aquafartis it goes black in about three weeks if I don't neutralize it.  You can go REAL dark with an application of Kibler's Tannic acid then followed up with his Auafartis.