Denis G. wrote:
On Jun 24, 10:40 pm, "Leon" wrote:
"Tanus" wrote in
...

Walnut will lighten? Does that work the same way as cherry darkens?
Make sure it gets sun exposure and leave it there to lighten up.

Yes



I have a walnut bowl that seems a bit dark and if all I have to do
is put it by a southern exposed window, I'd like to see how light
it gets.

I don't think it will lighten quite as quickly as the cherry darkens
in light exposure.

Here is a link to a Japanese book (“Wood and Cellulosic Chemistry” by
David N.-S. Hon, Nobuo Shiraishi)
http://tinyurl.com/knpd6f

According to the book, there are many causes of discoloration:
chemical, biological and physical. Results for light-induced
discoloration is shown in Table 7 for 100 species of wood (but Google
shows only part of the table) Positive numbers show woods that
darken and negative numbers show woods that lighten.

According to the Table 7, American walnut should lighten, but window
glass will block UV from sunlight, so it may take much longer than if
left in full sunlight outdoors.

Whoa, STOP. The UV content of sunlight on the Earth's surface is mostly UVA
(the UVB and higher has mostly been absorbed by the atmosphere) and window
glass unless it has a UV blocking coating on it is about 90 percent
transparent to UVA.