Aqua Fortis 101

[bioprof]

The question on this post seems to be about whether, and if so, HOW you neutralize the AF. So, Can you explain in more detail how you are neutralizing the Aqua Fortis. Great looking stock, BTW. I wish every AF stock came out that nice. Most are very much more dark in color.

If you make your own aquafortis and make sure that the acid can't dissolve any more iron, it shouldn't need neutralizing because all of the acid should be used up in the reaction. I've heard that the Wahkon Bay AF has HCl added to it, so it needs to be neutralized.

 

[rabjr]

Anything that is basic can be used to neutralize aquafortis that is too acidic. I use about a 10% solution of NaOH (lye).

I strongly suspect that the trick to getting good results with aquafortis is to use the right kind of wood. The best results, in my opinion, is with very hard sugar maple, the harder the better. It's been my experience that if you have softer spots in the wood, it will turn out almost black. Surface preparation is also important. I've noticed that in areas where it's hard to sand, the pores remain more open and it turns out darker in those places. If you have soft wood, burnishing it beforehand might help keep it from turning too dark. These are just my perceptions though and I may be way off track. :idunno:

Not sure why you replyed to me.

I have not built many guns but I have never run into any dark spots.

Hard Sugar Maple Defently colors diferent than Softer Red Maple. Don't for get you can do a Lye treatment before applying AF, like one does on Cherry, which helps with the color too. I have never done it but have seen some builders talk about it.

Before I learned some of the tricks here I made a paste of baking Soda and slobbed it all over to neutralize the Nitric Iron. I would reccommend easier ways to neutralize today. :haha:

 

[tallbear]

Bill
Once I've blushed it for the last time I find that the grain has raised some.I knock that down with some 0000 steelwool or a fine scotch brite finishing pad.This leaves some fine dust on the stock.I then put some ammonia on a clean rag and rub the stock down removeing the dust.You don't need to flood the stock just a nice even coat and rub it in around the inlays.I switched to the ammonia because the water needed to rinse the bakeing soda off(which will work if you want)raised the grain.Useing the ammonia just seems to solve the grain raising problem and kinda killed two birds with one stone .Once neutralized let dry completely and finish.

The color with aqua fortis depends on many things.The wood is one and the solution is another.Even though it takes some expermentation it it the best looking stain for curly maple.Part of the joy of gun building is the expermenting with traditional techniques!!!!!

Enjoy the journey!!!!!!!!!!!!!!

Mitch

 

[jbtusa]

Has anyone ever used an electric heat lamp to heat the aquafortis? A heat lamp would be a gentle evenly spread heat to prevent scorching the wood... ?????

 

[rootsy]

Nope but I am sure it would suffice if it can elevate the wood surface to the critical temperature needed to cause the reaction.

I use aquafortis on a lot of curly maple woodworking projects instead of stains. I generally blush it with my stove burner. I have a flat top stove and turn the burner up to high / medium high and pass the item over the top at a height and pace that causes blushing. You do have to be careful not to dwell or get too close that burner can cause some burning on corners, edges, etc.

I find a heat gun works best on gun stocks and larger pieces. First tool I ever tried when using aquafortis was the wife's hair dryer... no where near hot enough.

With a heat gun, as with painting keep the gun perpendicular to the surface at a constant height and pace.

 

[Tumblernotch]

I don't think linseed oil Kills or " neutralizes" the acid as much as it seals the acid away from AIR that it needs to react. There will be a minor amount of air in the wood cells, of course, but that is usually used up blackening the stock. The linseed oil seals the wood, keeping air away from the wood.

That could be. Whatever it does, it has the same effect.

 

[BillinOregon]

Fellas, thanks for all the fine advice. I think I know enough to proceed without disaster. I plan to use a propane torch very carefully to blush the wood.
Will post photos when I get time to do the job.

 

[rabjr]

Has anyone ever used an electric heat lamp to heat the aquafortis? A heat lamp would be a gentle evenly spread heat to prevent scorching the wood... ?????

I have no problem with a Heat gun.

 

[DTCoffin]

This gun was done with AF,1 good even coat and heated with a heat gun, I wasn't aware of neutralizing at the time and as you can see it is quite dark.Finished it with Tru-oil. http://i733.photobucket.com/albums/ww335/dtcoffin/100_1972.jpg http://i733.photobucket.com/albums/ww335/dtcoffin/100_1974.jpg

 

[NJStricker]

A couple of different things are going on when you heat the acidic solution on the wood's surface. One was mentioned before--the reaction with the iron oxide particles becoming embedded in the cross grain exposed in the curl of the maple, highlighting the stripes in the wood. The other is that the remaining acid reacts with the natural sugars in the wood when heated, further enhancing the grain and giving the wood some of its chatoyancy.

There is more sugar content in sugar maple than in silver, red, or big leaf maple, so the results are more profound.

 

[Soractus]

Those are some beautiful guns, guys.

Anyway, I'd read a description (apparently mistaken) somewhere listing Aqua Fortis as Nitric acid. Iron reacts with Nitric acid to produce Ferric Nitrate, which I've used in some of my goldsmithing.
It's a lovely brown color, I wonder how it would look? :hmm:

 

[Soractus]

A couple of different things are going on when you heat the acidic solution on the wood's surface. One was mentioned before--the reaction with the iron oxide particles becoming embedded in the cross grain exposed in the curl of the maple, highlighting the stripes in the wood. The other is that the remaining acid reacts with the natural sugars in the wood when heated, further enhancing the grain and giving the wood some of its chatoyancy.

There is more sugar content in sugar maple than in silver, red, or big leaf maple, so the results are more profound.

Aha! :thumbsup:

 

[rabjr]

My bottle says, "Nitric of Iron" on it. I'd have to look but I think it's 1-6 solution.

 

[LaBonte]

Anyway, I'd read a description (apparently mistaken) somewhere listing Aqua Fortis as Nitric acid.

Not mistaken but one of the points of confusion - in the old days pure nitric acid was known as Aqua Fortis, later the ferric nitrate mix made by dissolving iron in nitric acid was also called Aqua Fortis.

If you make your own aquafortis and make sure that the acid can't dissolve any more iron, it shouldn't need neutralizing because all of the acid should be used up in the reaction.

Your right it shouldn't but even the commercially prepared (almost pure) Ferric Nitrate crystals available from scientific supply companies require neutralizing or the stock will darken.
an example - the piece on the left was neutralized only on the top - notice how the vertical face is much darker due to not being neutralized and then exposed to the sun:

re: heat - the major reason is to make any remaining nitric acid more volatile so it will off gas.
You can get virtually the same effect as Aqua Fortis aka ferric nitrate with ferric acetate, iron dissolved in vinegar, but due to the higher volatility of the acetic acid in vinegar there is no need to heat or neutralize.

Some examples of both Ferric Nitrate and Ferric Acetate:

The top piece was done with some old Wahkon Bay AF as a control. On the lower piece three different mixes were used:
left - ferric acetate aka iron dissolved in vinegar
center - commercially prepared ferric nitrate crystals dissolved in distilled water which "makes" Aqua Fortis; they are available from the Science Company and other suppliers
right - ferric nitrate aka Aqua Fortis made by dissolving degreased steel wool in a bottle of Birchwood Casey Plum Brown, which is 10% nitric plus other acids (if you do this do it OUTSIDE with PLENTY of ventilation and in a large Pyrex bowl along with chemical rubber gloves, eye protection, and a good mask).

All pieces of wood were finished with a homemade period linseed oil based varnish.

 

[zampilot]

Nice pics and description LaBonte!
On my first rifle build the instructions for my AF said it does not need to be neutralized, and I verified that with the store! So, after applying a coat and blushing it, it looked great. A day later I installed the barrel just to keep the wood from moving on me, and removed it 3 days later to do another AF treatment. The AF that supposedly did not need to be neutralised did an excellent job of browning the barrel, even by fumes a 1/4" above the wood line!!!
I'll neutralize from now on, regardless.