Can artificial light speed up the natural darkening of cherry?—Michael Whitman

Richard Oedel replies: Yes, but artificial light is much, much weaker than the sun. Bright sunlight is almost 110,000 lux and a standard interior task light shining directly on the cherry would have about 1,000 to 2,000 lux. Don’t even bother. Instead, put it out in the sun.

With finish on, it is just fine since some finishes will also age and contribute to the darkening process. This is especially true of urethanes.

You might consider the same idea that many of us do. Mix up a dye or stain that you know will fade in sunlight. Match the color exactly, then wait. As the sun fades the stain and it becomes lighter, the cherry will begin to darken and the overall color of the piece will remain fairly consistent.

Bruce Wedlock replies: The natural darkening of cherry, as well as mahogany, oak and walnut, is a result of the oxidation of the tannin in the wood. This chemical reaction is accelerated by ultraviolet light, so sunlight promotes the darkening. To accomplish this with an artificial light, you would need intensity like sunlight to get a moderately fast result. It takes a couple of days of direct sunlight in mid-June to accomplish this, and you need to expose all the surfaces equally.
If you really want to darken cherry, the best approach is to apply a oxidizing chemical such as potassium dichromate, sodium hydroxide (lye) or fume with industrial strength ammonia (like Stickley’s mission oak pieces). I have experimented with all of these and recommend the potassium dichromate as the easiest and best method. It will age 15 years of normal oxidation in one day. While some will say it’s a dangerous chemical, the tablesaw is also dangerous. Proper procedures are perfectly safe in both cases.

I have written a detailed explanation on the process of aging cherry. You can get a copy by requesting Chemical Stains from wedlock@alum.mit.edu.

Bruce Hamilton replies: I don’t know. Do a test with some scrap to find out. Cover one side and expose the other then compare the two.

Wood