These book-match walnut boards show an optical effect that I would like to know the technical name for (assuming there is one). Here the light is from the left. When the light is from the right, the effect reverses. That is, the lower board is lighter and the upper board is darker.
I know why it happens. The wood pores (and finish) on opposite sides of the saw’s cut are 180 degrees from each other. So the light reflects differently from them.
Thanks for your help.
Replies
Hi John,
The apparent color change is caused by the direction of the wood grain. In curly woods, there's series of 3 dimensional stripes that alternate dark and bright as the wood is moved at slight angles. It looks like waves in the wood. The appearance of light and dark stripes is caused by differential light reflection. The exposed fiber ends of the wood as the grain curls through the board absorbs light and produces the dark bands. Reflection and diffraction from fiber walls cause the bright bands. Because the wood fiber walls are curved sharply and act as concave or convex reflecting surfaces, changes in the angle of view or incident light makes the apparent waves seem to shift; the light stripes appear to becomes dark and the dark stripes appear to become light. The same sort of effect is taking place in your wood; though the wood fibers are aligned in one direction.
I've heard the effect called chatoyance, directionality, or shimmer.
Paul
http://www.finishwiz.com
Thank you, Paul, for a comprehensive description. A Google search on "chatoyance" and "wood" delivered almost 700 hits. My dictionary says it is pronounced sha toi ans.
Does anybody know of wooden objects that move and take advantage of this effect? I guess I'm enchanted with it.
LASER and Holographic?
I've seen pictures of some parquetry that uses this effect very dramatically. Diamond and reverse diamond veneer patterns also.
Chatoyancy. The word comes from the French for "to shine like a cat's eye". The term is more commonly applied to gemstones, but is also used for wood.
The French origin is why the pronunciation is odd.
Kinda like when you brush suede or corduroy in different directions and can make patterns.
I never knew there was a name for that effect, guess there's a name fer perty near everthin...
David C
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