The fuming technique is a pretty traditional British technique for darkening oak (lots of tannins in oak). I was told by a Brit-trained architect that they used to bury oak timbers and boards in piles of manure (lots of ammonia produced by the manure) until they got the color they wanted. I have tried fuming small pieces in a sealed container with liquid ammonia, and it does work, but it's slow. A quicker method to get to a similar color is to brush or wipe a solution of potassium permanganate on the wood, then wipe with water to stabilize the color. I have used this on oak cabinets with good results, and it gives a color that I cannot duplicate with stain. There is a lot of literature on this technique, and a Google search will turn up info on potassium permanganate and potassium dichromate for darkening tannic woods.
