Ever walked around your rich relatives new silk rug and notice the color and sheen seems to change as you circle. Or when mowing your grass, the left to right pass looks different from the right to left pass. Or vacuuming the rug. These are all manifestations of chatoyance.
Chatoyance is caused by light being reflected differently by the variations in the reflecting surface. Grass leaning to the right reflects light differently than the same blade leaning to the left. When you vacuum a rug you change the direction of the nap. If you back brush velvet (or your cat), you change the way the fibers lie and change the appearance.
Interesting, but what does that have to do with woodworking? Wood has grain, grain changes direction causing changes in appearance of the wood. The look of highly figured wood is caused in part by the grain changing direction. Some of it may be due to the color variations but not all. Rockler has an article about chatoyance HERE.
Chatoyance also explains why book matched veneers and resawn boards may look similar but not match exactly. When you resaw and flip a board, the grain that was rising at 5° on the left board is diving 5° on the right board. Walk around and the effect reverses.
What makes me write about this is a veneered chest I saw at an auction on Friday. It is one of the most pronounced color shifts I have seen. Take a look:
A fairly dramatic shift, don’t ya think.
An interesting note. I went back Saturday morning to try to get better pictures. It wasn’t far out of the bank, landfill, Home Depot loop. Turns out the auction started an hour early and this very chest was being auctioned. It sold for $400, a fair price but more than I am willing to pay for it.