Fuming and Moisture

[Tony West]

I am working on a finish for a mission style bed. It is white oak and I'd like to fume it. I've fumed several small samples according to the methods outlined all over the internet (small dish with 10% ammonia inside a sealed chamber...aka garbage bag).

I am getting very dark pieces...after a little BLO almost black. That's after about 8 hours of fuming. This is simply too dark. I don't have an air conditioned shop, and it's very humid here...I likely have 'wet' wood.

I tried a piece of white oak from a friend that went straight from the kiln into his air conditioned shop, fumed it for 10 hours with the same method and the wood is still dark, but the grain is visible...it's not almost black after the BLO is added. In other words, perfect coloring. Same methods.

Does the moisture content of the wood change the fuming process? More moisture = darker fuming?

Could it be that the different logs of white oak are taking the fuming that much differently? I can see subtle variation but this is ranging from pleasing chocolate brown with good pop on the rays to almost black and minimal rays visible.

I have all my pieces finished with a ROS to 150 grit...do I need to go finer...never have before, but then again I was staining or BLO'ing the piece, not fuming.

Any help would be appreciated! Thanks!

[Joe Chritz]

It is on my list of stuff to get to so I have no personal knowledge but I think the time is the variable factor in the coloring of the wood.

Try leaving the pieces for 1 hour, 2 hours, etc and see how the reaction is in color.

Joe

[Dan Hulbert]

I have done some fuming in the past, mostly small projects. My experience is that the moisture of the wood is not a factor, but rather the tannin content of the wood. Fuming is the reaction between the ammonia and the tannins. Tannin levels can and do vary significantly among trees. I have never been able to achieve the darkness you describe even after fuming for 48 hours. Obviously, your wood has a very high level of tannins. Cut back your time and try again. If you are getting that dark in 8 hours, I might suggest trying 2 hours.

Your tannin levels are likely to vary among your boards if they are not all cut from the same tree, you may have to adjust your finishing schedule accordingly.

Test and test again.

[Scott Holmes]

Fuming is a dangerous and difficult to control method of coloring wood.
Fuming is an old fashion way, when they didn't have access to the wounderful coloring agents when have today.

Why not use an alcohol dye like TransTints and be done with it? Very easy to use very easy to control the color.

[Steve Schoene]

I agree with Scott. Dye is much simpler.

I would also point out that aside from the differences in tannin in the wood, the temperature would also be an important factor since virtually all chemical reactions are accelerated as temperature increases. That's almost certainly more important than differences in the moisture content of the wood.