Wood color change with sunlight

[John K Jordan]

If you get the AAW emails you may have already seen this, in the email that came a few days ago. (If not an AAW member, it's worthwhile joining.)

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attributed to Alan Miotke, Mount Prospect, IL

This test seems a bit extreme since we seldom store woodturnings in direct sunlight (to avoid any bleaching), but I think it's interesting all the same.

My experience is close to this photo except most of the Jatoba I've turned started out darker than that in the test and hasn't changed much (yet). I've seen Padauk turn very dark like that; I quit using it. Osage Orange is not in the test but what I've used starts out very yellow but turns a much darker orangish brown quickly. And as most know, the red in Box Elder fades very quickly in the light, a little slower in a darker environment.

This test doesn't address if any color change is due to oxidation. I have some old Cocobolo and while the inside is beautiful with color the outside is dark brown all the way around, almost black, and extends a bit into the wood. It's hard to know how much of that is darkening is from light, from air, or from something else completely but based on the photo above I suspect it's not the light. In normal conditions out of the sunlight, the Cocobolo loses the beautiful oranges and reds and slowly turns darker.

I think a better test would compare similar pieces:
- in air with no light,
- in light with no oxygen,
- in air+sunlight,
- and in a normal environment - inside the house on the shelf out of the sun!
Control pieces should be kept in a dark chamber with inert gas.
An even better test would include pieces of the same wood covered with various finishes exposed to the same environments. Maybe if I find myself with nothing to do one day...

For those interested in color change and how to prevent it, this is worth reading. I has a nice list. The article discusses exotics but much applies to domestics.
https://www.wood-database.com/wood-articles/preventing-color-changes-in-exotic-woods/


JKJ

[Leo Van Der Loo]

First off that color chart is way off, just look at the Walnut, I have never seen any walnut that color and the same applies for the other ones on it.

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As for color changes in wood, and I’m speaking of my experience, not going by what someone is claiming, all the colors of wood do change, keeping them out of the light or in diffused light will slow down the changes, not stop it.

Just yesterday I picked up a piece of Manitoba Maple with some red coloration in it, still showing after several years laying around in my wood supply storage, turning it over showed a much redder color on the underside.

I know for sure if that piece had been sitting in my house that red would have been changed to a reddish brown, the Padauk and purple heart Osage etc all have changed, some do it faster than others.

[Steven Taffs]

I have a bunch of Nicaraguan cocobolo with the tight grain, it's very yellow after cutting or turning. Takes about 6 months to a year of sun to get the reds and oranges. Great for gifting pens as it just gets better with time.
Lots of the large grain Mexican cocobolo I've seen is very red/orange with the dark almost black swirls once cut but turns a dark blander brown in sunlight. I like to used this inside a box when I have it.

Padauk I used a lot in the past, a few fly fishing boxes i made of curly Paduak are still gorgeous inside but almost no curly or red left on the outside after 4 years or so.

[Dave Fritz]

Only dealing with local hardwoods, cherry, walnut, maple, elm, hickory and oak, I tell people generally dark woods lighten and light woods darken. Make sense? I don't want them to be disappointed. No experience with exotics.

[John Blazy]

The trick to keeping color (if you plan ahead in the design) is to try to use brightly colored woods in areas that won't be exposed to sunlight, like drawer interiors, underside of lids, inside of cabinets, etc. I had the most brilliant canary yellow African Satinwood, and knew it would dull, so I used it on the inside of my boats mahogany doors. Stayed bright yellow for many years, - only recently starting to get more brown. The mahogany, OTOH, just gets better with age.

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[John K Jordan]

I can't remember if I posted this link in this thread, but I think the Wood Database article on color change is worth reading:
https://www.wood-database.com/wood-articles/preventing-color-changes-in-exotic-woods/


The trick to keeping color (if you plan ahead in the design) is to try to use brightly colored woods in areas that won't be exposed to sunlight, like drawer interiors, underside of lids, inside of cabinets, etc. I had the most brilliant canary yellow African Satinwood, and knew it would dull, so I used it on the inside of my boats mahogany doors. Stayed bright yellow for many years, - only recently starting to get more brown. The mahogany, OTOH, just gets better with age.

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[John Blazy]

That is a great article John!! "Their Chromatic Fate" is excellent, as well as the reference to our delusional expectations.