Ammonia Fuming

From RISDpedia

Ammonia Fuming is a process in which white oak is exposed to the fumes of anhydrous ammonia. The fumes react with the tannins in the wood, which produces a gray color on the surface of the wood. When treated with Watco Danish Oil, the wood turns a deep brown color.

This process was developed by Gustave Stickley for the Arts and Crafts furniture he made and sold, as a way to approximate the coloring of English Brown Oak, which is not avavilable in the United States. It is still used today by furniture makers who want to replicate the look of turn-of-the-century Arts and Crafts furniture.

A note of warning: Ahnhydrous Ammonia is EXTREMELY DANGEROUS. It is very caustic and must be handled with care. ALWAYS WEAR A RESPIRATOR WHEN HANDLING THIS CHEMICAL! Household ammonia is usually .5% - 3% ammonia to water. Anhydrous Ammonia is 23%. The fumes are really strong, so it should only be opened in a well ventilated area. This does not include your kitchen. Anhydrous Ammonia can be obtained from Blueprint Supply websites. it is only available by the gallon, and requires a $20.00 hazmat handling fee.

That said, nothing in the world looks as good as fumed white oak. I have not yet found a combination of finishes that really matches it.

To fume oak, build an airtight tent around your object with plastic dropcloths. I like to try to use a clear plastic so I can check on the progress without having to open the tent. Pour about 1/4 cup of anhydrous ammonia into a glass container, place it in the tent, and seal the tent completely. Dedending on the size of the piece, and the roominess of the tent, you will probably have to wait between five and twelve hours. My experiments have show that after about twelve hours, there is not a significance in color change.

To dispose of the ammonia, mix it thouroughly into five gallons of tap water. This will dilute it enough that it can be poured down the sink.

Do not sand the work after you fume it, as you will sand off the top layer of the wood that has reacted with the fumes, and it will look like white oak again.

You can use this process with other woods, but you have to brush on tannic acid, so the fumes will have something to react to. I have not really liked the colors as much when I use this on anythign other than white oak.

Italic textFine WoodworkingItalic text Magazine has a couple of articles about this process that are a little more specific.