Dark Wood Flooring, Brown or Black Floors colour is achieved with one of three techniques. One method used is to stain the wood with colour oils or lacquers. The second method is to smoke the floor and the and third is to put the wood through a heat treated process called carbonizing where the wood is darkened all the way through.
Smoked or fumed wood is achieved by exposing the wood to an enclosed atmosphere of heat and ammonia. Fuming occurs when the ammonia reacts with the tannin in the wood and permanently changes the colour of the wood. Depending on the time and quantities used a certain level of darkness can be achieved. Fuming is also somewhat unpredictable as boards will react differently and therefor have more colour variation as opposed to staining which will be more uniform.