Fuming is a greying of wood, a colouration technique that is generally but not exclusive reserved for oak. The treatment is such that the natural wood colour is deepened until it reaches the same grey as would be achieved either naturally over time, or by dipping planks into baths of lye. This ageing technique was apparently discovered when oak boarding that was stored or used in stables darkened over time by close contact with the ammonia fumes from horse urine.
It’s quite possible to fume your own oak given the space and will. In any case to fume wood, it needs to be placed within a sealed chamber, which may be a room or some other container depending how much is to be fumed. The timber must be spaced so that air can circulate all around it. It is then left with an open tin of ammonia for as long as is necessary to change the colour of the wood. The active ingredient, ammonium hydroxide, reacts with the tannins in the wood to create this smoked, fumed, effect.
How long this takes depends on the quantity of timber, the size of the chamber and the depth of colour required. It can be minutes, hours or days, but doesn’t need weeks or months. The ammonia fumes are strong enough to warrant full protective gear.
It is also possible to leave bowls of ammonia in a sealed room to darken an existing oak floor; this is something we have done ourselves, but it’s not a DIY project.
* Because the treatment permeates the timber the greying, unlike a stain, doesn’t ‘walk off’; this means that it can be re-sanded, repaired – whatever is needed over it’s lifetime.
* Fuming was first popular in the 19th-20th C with the Arts and Crafts Movement. In 1901, Gustav Stickley took it to the US to create the solid, oak furniture known as Mission Style. Today we use the technique more for flooring and accessories- door handles etc. than for furniture.