AsphaltCowboy, I really appreciate the information you gave above.. I had absolutely NO knowledge of that process at all.. How do you do the actual fuming process? You mentioned a 'barrel'.. ???
It's so easy even a cave man could do it.
Be forewarned; once you fume, it CAN NOT be undone. Unlike stain which can be sanded out ammonia fuming is through and through. A four inch square of say maple will be the same color in it's center as it is on the outer surface.
The barrel I use is one of the cardboard dry chemical barrels that our plastic colorant comes in at work. You could simply use a large trash bag, but I always worry about the ammonia gettin' spilt so I use the barrel.
Of all the hardwoods I've no idea which contain tannic acid naturally other than walnut and oak. You won't need it for those. Maple for sure does not, and will need treated. I can't remember for sure about cherry.
Since a quart size tea bag is more convenient and cheaper than buying tannic acid I use those. Put the tea bag in a standard 12oz coffee mug, fill 3/4 or so with water and nuke it in the micro-wave to brew and then let cool.
You can put this on naked wood at any time, but I wait until I'm ready to whisker the stock and use the tea for my first whisker. Just slobber it on and let the stock dry, you can whisker or not afterwards, your choice.
Now for the ammonia and be careful with that stuff, it can strangle ya', best done in a well ventilated area or better yet outside. Half a cup is more than plenty. Put a small dish of some sort in the bottom of the barrel over at the edge where you wont bump it with the stock and pour a bit of ammonia into it. Next place your stock in and cover the barrel. If you use a bag just tie the top shut or clip with a large enough cloths pin or something.
Some woods will react faster and get darker than others, depends on how hard and dense it is. Each individual piece of wood is different. Harder=slower not as dark, softer=faster and darker (this applies to blond woods like maple, walnuts can actually turn black). For a one piece stock of rock maple I just put it in and forget it, Two piece sets can get tricky, unless you specifically requested it you seldom get a forearm blank which was cut from the same area of the wood slab. Even a piece from the same tree may react differently. For these I recommend a simple egg timer. The butt usually is the hardest, so fume it first. Check frequently and when it looks dark enough remove it. The process stops almost immediately. Here is where you really need the egg timer (and where I screwed the pooch with my A5). Set the timer in five minute intervals and check the progress. You can touch it, the ammonia won't harm your hands unless you're sensitive, so take it out and compare it to the butt. When the color starts getting close set the timer for shorter intervals until you get a match. The wood will take on a nasty yuck look on the surface, just ignore that it'll sand off when you do your whisker.
You've really got to watch walnut, too much time in the fumes and it can often turn black or near to it. You can also almost, get a faux ebony if you leave it overnight or longer.
I've had a lousy day so if I've confused you with any of this, let me know, I'll clear it up tomorrow when my head is where it belongs.