Fumed Engineered Oak flooring is made in our factory where we manufacture wood flooring by placing the raw material top layer veneer which can be between 5mm to 8 mm thick in a sealed enclosed chamber.
The fuming of Oak is carried out to bring out the natural tannins in the Oak, ammonia brings the tannins to the surface and the colour variation you will get naturally is because each piece of wood is unique and some will have tannins near the surface and some deeper down. The nearer the tannins are to the surface the darker the finished board. You can get a rich brown to a virtual black colour. The longer the boards are left in the chamber the darker they become.
For more information, click here: http://www.thesolidwoodflooringcompany.com/fumed-engineered-dark-oak-flooring-c-30.html