This week I have been experimenting with a process know as 'ammonia fuming'.
It is a wonderfully traditional and interesting technique that was discovered when the oak beams in stables were observed to have darkened over time.
"Some oak boards stored in a stable in England were found after a time to have taken on a beautiful mellow brown tone and on investigation this change in colour was discovered to be due to the ammonia fumes that naturally are present in stables." [Gustav Stickley, in "Craftsman Homes" (1909)
It was then deduced that it was actually the tannins that are heavily present in white oak that were reacting with ammonia to create this beautiful, slightly aged look. Stickley was thought to have used this process in his workshops along side staining during the 'arts and crafts' era (see picture above).
It is really quite an enjoyable and fascinating process. The ammonia (which is a little eye stingingly nasty) does not need to come into contact with the wood. The piece that is to be fumed is placed in a 'fuming box' or 'tent' (an airtight container) with a shallow dish filled with ammonia. It is then left to work it's magic. It starts out a little grubby looking then gradually turns a light mocha colour and eventually becomes a beautiful chocolate brown shade. Interestingly different parts of the tree have different levels of tannins so there is a variation to the end result. The sap wood for example which before fuming would be, to a casual observer, no different to the rest of the board has no tannins and so does not change during the process.
I personally believe that at all stages it is stunning. It really brings out the grain in the oak; the medullary rays look beautiful. A much richer, deeper colour is achieved than that produced through staining; it is the chemistry of the pigment in the timber that is being affected. Once the finish has been applied the effect is enhanced measurably.
I do not have photos just now of my own fuming attempts so we will have to be content with the charming work of Mr Stickley.
Farewell for just now,
Little acorns xxx
ps. for the health and safety people reading this... please do wear a mask, eye protection and gloves when dealing with ammonia as it is a little unpleasant! x