Sunday, August 30, 2009

Fuming... (Oak, Not Mad)

Of the six boxes I currently have in progress, four of them are made with some of the reclaimed white oak I got from an old house on our family farm. Having been a while since I'd done any fuming, I thought I would take the opportunity to pull out my supply of Ammonium Hydroxide and make some chemical reactions happen.

Before I begin, I would like to offer a few words of caution...

Ammonium Hydroxide is a seriously dangerous chemical and should be handled with caution. As the warning on the bottle says, don't allow it, or the fumes, to come in contact with eyes or skin and don't ingest it. I'll add to those warnings that if you have any open cuts exposed to the air, you should make sure and cover them, as well.

I never work with ammonium hydroxide in a closed environment - always out on the patio or my driveway. I use full-coverage chemical-resistant eye goggles and a partial-face respirator rated for organic vapors (my mask uses 3M's 6001 filter). This is not the kind of respirator filter you will ever find at Home Depot or Lowe's (read the warning labels on the filters - they all specifically say they are not rated for organic vapors), though you can get them on-line easily enough. I happen to be married to a woman who has to have one just in case she is sent to a site for groundwater sampling that requires it, so... mine was free. I use the blue nitrile gloves because they are chemical resistant (and because I'm a cuticle biter and my fingers BURNED the first time I tried this without using nitrile gloves, hence the additional warning about cuts exposed to the air).

That said, woodworking is full of dangerous tools. If you don't take the time to become familiar with the tools you're using (whether they be mechanical or chemical), then you should fully expect to receive some time of injury at some point in your woodworking career. Have respect for and an understanding of your environment and you will decrease your chances of getting hurt. Now back to the blog...

My basic fuming setup is simple. I don't bother with wooden frame and plastic sheet tents. They're too easily damaged and something you don't want is a leak in your fuming tent.

Instead, I use an old Igloo chest cooler (which became obsolete after I purchased one of those wonderful 5-day coolers several years ago). It has an air-tight lid and is plenty big enough to fume several boxes at once.

It came with an open mesh basket that sits on a lip at the top of the cooler. I pour my ammonia into a plastic sour cream container, set it into the bottom of the cooler, and then turn the mesh basket upside down and place it over the container. That allows me to set boxes directly on top of the basket and not worry about tipping the container over.

I always fume several cutoffs from the same boards I used to make the boxes. These become test pieces for determining what finish I will use later on.

Once I get the ammonia inside and cover it with the basket, I place my boxes on top of the basket and lean my sample pieces against the side. Then I close it up tight, put a few pieces of painter's tape across the lid and tape a note on top that indicates I am fuming wood inside (to prevent me or my wife from accidentally opening the cooler). In order to get the best results, the container should be kept in a warm or hot environment. In the summer, nothing is hotter than my garage. Yesterday and today have been notably cool, so I was a bit concerned with how it would turn out.

It was, however, wasted emotional energy. As you can see, after 24 hours in the fuming tent the oak has darkened quite a bit. The wood in the lower part of the picture to the right is un-fumed white oak from the same board; in the middle are my sample pieces; at the top are my two boxes.

This image is also useful to point out how heartwood is affected by the ammonia much more than sapwood. Had I used sapwood in either of the two boxes I fumed (I specifically did not fume one of the four boxes based on a small amount of sapwood in one side), I would have some creative fixing to do with dyes and stain when I reached the finishing stage.

Before I do anything else with these boxes, I have to let them off-gas for at least 24 hours. After that, I'll work with my sample pieces to see what finish works best. I have some idea as to what I want to do, but I always test it out on sample pieces because each batch of wood can react differently to the ammonia. But generally, it involves a coat of BLO (boiled linseed oil) and a few light coats of amber or garnet shellac, depending upon how dark I want it to look in the end.

I will most likely spend some time with an inlay or two in these boxes, however, so I have some time before I worry about a finish.

Maybe while I'm in the fuming mood, I'll run some sample pieces for you to show you what other kinds of wood I've fumed and take pictures of what these woods look like fumed and un-fumed.

If you plan on trying to fume a woodworking project in the future and have any questions, let me know. I'll be happy to share whatever knowledge I have with you.


Ethan said...

One note of warning I forgot to mention... always put your ammonia in a glass or plastic container when fuming - never put it in metal.

At the very least, the ammonia (especially in this strength) will begin corroding the metal container. I'm not sure what kind of chemical reactions might occur with different metals and what the resulting gasses could be, so... I play it safe and stick to my plastic sour cream container.

Ethan said...

Recently updated this thread to correct something.

I use Ammonium Hydroxide (ammonia/water solution) and NOT Anhydrous Ammonia (concentrated ammonia with the water removed - i.e. pure ammonia).

Sorry about the confusion.

Anonymous said...

Hi Ethan,

We are considering fuming oak for the inside of a whole room. I have read in a few places that the wood needs to be aired out after it is fumed. Could you give me a sense of how long it needs to air out and if there are any residual ammonia fumes in your experience?

Thanks so much.


Ethan said...


Sorry for the delayed response!

My experience has been that 24 hours is plenty sufficient.

My current batch of boxes has gone... about 9 months? (er... they got shelved when I moved into a significant step of shop renovation and I've not pulled them back out.) There is DEFINITELY no lingering ammonia smell on them.

All joking aside, when they're done off-gassing, the ammonia smell is completely gone.

That said, fuming an entire room is a HUGE difference from a small box. I imagine it would take longer for the fumes in an enclosed room to dissipate completely. Lots of fans and some good air circulation through open windows would help, I'm sure.

But please be careful! That much Ammonium Hydroxide would knock a person flat out with really bad effects. :(

Oh, and I'm totally jealous that you have an ENTIRE ROOM to fume with ammonia! Be sure to take before and after pictures... and link when your done! Would love to see it!