Being rushed for time inadvertently leads to the discovery of a new technique. For decades, chemical fuming has been used to change the color in different woods.

This photo series shows: top, the natural color wood samples; middle, samples brushed with ammonia, and bottom, samples completed with clear coats.

 Depending on the size of the wood, small pieces can be fumed in an enclosed box or just about any container that is sealed, while the larger pieces of wood are usually done by erecting a plastic tent or using a room that is sealed during the fuming process.

The wood is placed inside the tent or the sealed room and plastic or glass containers are filled with liquid ammonia and placed inside the enclosure, which is then sealed. As the ammonia begins to release its noxious fumes inside the enclosed space, it starts the chemical fuming process on the wood.

Many species of wood contain a substance called tannin, and the ammonia fumes react with this yellow or brownish substance. The fumes penetrate into the wood and bring out different shades of color. The more tannin, the better the wood will fume.

The length of time that the wood is fumed and the temperature inside the room or tent are important factors in the process. Another factor is the percentage of ammonia used in the fuming; the higher the percentage, the faster the process goes. Also, the color can take hours or days to achieve, depending on the wood species.

I am not an expert on fuming, although I have fumed many pieces, read numerous articles on the subject and interviewed others who do fuming on a regular schedule. It is a very interesting art and is still popular with some woodworkers today.

To create a tent for fuming some small pieces of wood, Mac Simmons used this small black plastic bag, which worked well.

Desperation Produces a New Technique

I wrote about fuming in the September 2006 issue of CWB, describing the standard process and some alternatives that can be used to achieve a similar look. But, I recently was doing a photo shoot where I needed some fumed samples in a hurry and inadvertently discovered another technique that I want to share here.

I began in the usual way: After setting up a small plastic bag as the tent and placing some pieces of wood inside, I filled two plastic containers with ammonia, sealed the tent and waited for the wood to fume. During the early evening and throughout the night, the weather got cold. So in the morning, when I went to check inside the tent, there was very little change in color.

I brought the tent into my garage and opened it up. I needed the photos right away, so out of desperation I took a sample piece of wood and brushed on some ammonia and saw that it actually colored the wood. I brushed on more ammonia, and the color got more intense. I let it thoroughly dry and then sprayed it with clear lacquer. I was very surprised at the results, as it had a nicely fumed color. I then started playing around and found out that I could lighten or darken the colors by adjusting the amount of water that I added to the ammonia.

This turned out to be a unique coloring technique, and I was excited about these findings. Also, I now had another interesting subject to write about. I “went wild,” testing some small samples of wood to see what colors I could produce. I realized that this process is so simple that all I have to do is show or tell someone what I did, and then all they have to do is some tests on different pieces of wood. They would have an easy way to get the look of fumed wood and a new way to stain wood to get different colors.

From the Beginning

First, you must always wear personal protective gear whenever you are fuming or working in your shop. Since you will use household ammonia, you should wear a rated respirator and have good ventilation. You should have all your materials prepared in advance, including the ammonia, containers, prepared wood, synthetic brushes, water and the clear coating.

Your wood should be clean, well sanded and free from any dust or other residue. You start by pouring a small amount of ammonia into a small glass or plastic container. Use either a polyfoam brush or a synthetic bristle brush and brush several different pieces of wood with the ammonia. Try brushing one coat on some pieces and two coats on others to compare the results.

Be sure to mark each piece of wood on the back side with all the pertinent information and save the samples for future reference. Allow the samples to dry completely for several hours, then apply a few clear coats so you can see the final color of the fumed finishes.

From my sample testing, I knew right away that brushing on the ammonia worked. It also reinforced something I always stress in my teachings and writings — the importance of making start-to-finish samples.

As I mentioned above, the wood must have tannin or you may end up getting some unpredictable colors. Results also will vary, depending upon how evenly you apply the ammonia. If you stain small pieces of wood and apply the same amount of brushed or sprayed ammonia, you will get an even color stain. Where you do not apply the same amount of ammonia, there will be a variation of color.

This definitely applies in cases where you want to decrease the color strength by adding water. To lessen the chance of problems in this situation, always measure your ammonia and water and keep accurate records, making complete samples, including clear coats.

In some cases, you may run into color variations that cannot be corrected by the ammonia. To correct such problems, I recommend that you make up extra color stain to be used with either an airbrush or spray gun to blend or shade the wood to make the different colors uniform.

Another problem you may run into occurs when there is heart and sapwood in the pieces. In that case, I mix up dyes and/or pigmented colorants and use the airbrush to unify the color. I then apply clear coats to protect the finish. This same coloring technique is used in true chemical fuming and also in the art of fine furniture finishing to make color adjustments as needed.

These are nine different wood samples stained with various dilution combinations of ammonia and water.

To Review the Process

Follow a scheduled plan, and always start by wearing protective gear. Then, begin by inspecting all your wood. If you find defects, you must repair them. If you don't take care of them, they will still be there at the end of the finishing process.

Use a piece of the same species of wood that will be used in the actual project to make up samples. Have all you finishing materials ready; in this case, have enough ammonia and water to do the entire job. Also, be sure you use the same brand of ammonia throughout the project.

If you are brushing on the finish, have various size brushes handy. As you are working, the brush may pick up the fuming colors. You can clean the brushes in some ammonia, using clean water to flush them clean. Keep records of your ammonia mixture formula if you are making color combinations to lighten or darken the wood.

If there are color variations in the wood, you can correct them after the ammonia is thoroughly dry by airbrushing with almost any coloring medium. Then protect the finish with almost any clear coat.

Remember to always work in a well-ventilated area and wear personal protective gear whenever you work with ammonia. I know that once you give this unique finish a try, you will begin using it on many future projects.

Mac Simmons is a freelance writer and 50-year veteran of the furniture finishing, refinishing and restoration trades. Mac has written articles for woodworking magazines in the U.S. and in the UK, Austria and Canada. Questions may be directed to him in writing at 400 Knightsbridge Pkwy., Lincolnshire, IL 60069.