Traditional Fumed Finish for White Oak

1 With full safety gear in place, lower the fuming chamber over the project and a tray of concentrated ammonia.

A simple approach to this classic finishing technique.

Finishing options abound in the woodworking world, however with Arts & Crafts style pieces, you need to get the finish right to complete the feel of the piece. This isn’t a project made from birch plywood, where an opaque finish might suffice. There are several finishing schedules I’m happy with, but a traditional piece such as the Limbert No. 239 Tabouret on page 34, I decided to use an ammonia fumed finish. Fumed finishes were synonymous with the Arts & Crafts movement over a hundred years ago and are still being explored to this day.

Preparation is Key

The first step is to tent the table in a fuming chamber. I scabbed together a frame from strips of plywood and covered it with clear plastic sheeting. Be sure to tape the seams to seal in the fumes.

The second step is to procure safety gear for yourself as it is paramount when working with concentrated ammonium. Don’t even crack the lid open until you’re wearing a respirator with cartridges approved for organic vapors and have donned splash-proof googles. If you can’t find your old googles from chemistry class, swim googles will work in a pinch.

Start Fuming Process

Place the table and octagon top in the chamber and slide a container of 28% industrial-grade ammonium inside. Elevate the octagon top on painter’s pyramids or something similar to be sure the fumes react to all surfaces. Also include a few scraps of white oak in the fuming tent, which will prove useful in monitoring the coloring process.

2 I chose a fume duration of 4 hours and applied two different Watco Danish Oils to fumed and unfumed samples. From left to right: unfumed black walnut, fumed black walnut, unfumed medium walnut, fumed medium walnut. I selected the fumed medium walnut color.

Check on the sample boards in the chamber periodically to see how much color change you’ve achieved. Don’t be surprised if the color change with ammonia alone isn’t dramatic. The real change happens when you apply oil to the project. What you’ll notice is the fumed samples will be much darker than the oil-only control samples. The samples pictures in Photo 2 have only been wiped with Danish Oil at this point. The color becomes even richer once a topcoat is applied.

3 While the fumed white oak looks a little flat, the first hint of oil reveals the deep rich color the fuming process provides.

Apply Watco Danish Oil

Once the project is fumed to your liking, which was 4 hours in this case, let it off-gas for a day or more. The next step is a Watco Danish Oil in a medium walnut color. If you’ve never worked with Danish Oil, you’re in for a treat. I find that it’s the singular easiest-to-work finish that I’ve tried. You won’t struggle with uneven coverage, dark spots, or smudges that other finishes can cause. Danish Oil, unlike stains and dyes, doesn’t seem to get darker if you go over an area twice. In fact, when I’m using more complicated finishing schedules such as stain-over-dye techniques, I need to have a helper in the shop. By contrast, this oil finish can easily be applied by yourself, and you don’t even need to hurry!

4 Take your time. When wiping Danish Oil, you can twiddle your thumbs a bit because it doesn’t tend to blotch, streak, and create dark spots as some dyes and stains will.

Lastly, Apply the Topcoat

Once the oil has fully dried, apply the top coat of your choice. Here, I sprayed a lacquer topcoat in a satin finish. Two coats of lacquer with a scuff sanding in between works well for most furniture. The final coat is wet sanded with 1500 grit soft sanding sponges and soapy water. One benefit of fumed finish is the way it penetrates the wood fibers deeply. This means you’re less likely to sand through the finish when performing the final scuff sanding and wet sanding steps. With the flexibility this finishing schedule provides, I’m sure you’ll be adding this to your finishing favorites as well!

5 Here, a sprayed lacquer finish brings out the rich, nut-brown color of the fumed and oil finish. Two coats with a quick scuff sanding between are all it takes.

Tips and Tricks

Select the best pieces to use.

Remember that with a fumed finish, we’re using ammonia to react with the tannins in wood. The goal is to bring out the character of the wood itself, rather than obscure the grain. This process won’t hide blemishes in the wood, so select your best white oak pieces for fumed projects. One more word of caution ­when fuming white oak … if there’s any sapwood in your finished project it won’t darken the same way heartwood does.

Fuming doesn’t work well with all lumber species

Fuming only works well with lumber species that contain high tannin levels. If you want to fume other types of wood, be sure to experiment with sample boards