Sunlight aging

[phinds]

Which ones are you thinking about when you mention oxidization?

First one that comes to mind for oxidation is Eastern red cedar (aka aromatic red cedar) but sycamore can also have a dramatic, and FAST, response to oxidation when it's first cut. There are others, but the sawyers here probably are more familiar w/ it than I am since I don't deal w/ unseasoned wood, especially freshly milled wood.

Eastern red cedar


sycamore

 

[Arn213]

Brazilian pernambuco would quickly oxidize if you have direct sunlight- very noticeable and could be done in a day. The same with the “wannabe” pernambuco, chakte viga/paela- has the same tanning results.

 

[phinds]

redheart is another one that fades quickly with UV

 

[phinds]

oxidize if you have direct sunlight

?

Oxidization and UV are quite different effects

 

[Arn213]

?

Oxidization and UV are quite different effects

Both on oxidation and UV- just had my 2 cups of coffee after posting. I’ll post a photo if I can locate one of my planks on my file.

 

[Arn213]

@phinds & @chatometry- see 2 panel photo’s on the left and you can see where the sticker marks (yellow) are compare to the exposed parts (orange) where you can see vast difference in color change/transformation.

 

[chatometry]

@phinds thank you. ERC is one we will soon process. So I guess you would suggest testing straight after sanding, and then after X days (of oxygen but no light exposure) expecting a change (in appearance).
London plane is "Platano" in Italy - no idea why it is the same word as a sort of south-american banana.

@Arn213 thank you. What exposure was there on those Pernambuco pieces? Just oxygen, or light too? And how long? (days, weeks, ...?). I used Pernambuco once (years ago), but I did not look at this effect :(

 

[phinds]

Both on oxidation and UV-

Sure, but often one or the other dominates and for many woods, whichever one dominates, it does so very strongly in the first few hours or days after milling. In my experience, most woods that change color due to one or the other do so more from UV than from oxidization. Sycamore is a strong exception.

 

[DLJeffs]

Purpleheart seems to change fairly quickly, going from that beautiful deep purpley-red to grey. Faster in direct sun. So is that a combination UV and oxidation?

 

[Arn213]

@Arn213 thank you. What exposure was there on those Pernambuco pieces? Just oxygen, or light too? And how long? (days, weeks, ...?). I used Pernambuco once (years ago), but I did not look at this effect :(

The two panels to your left was oxidation and natural light through the 3 windows at the opposite wall- strong sunlight in the morning, but I have blinds to filter that. Those were put on stickers when I reorganized my shelving unit about 6 or so years ago. But, these are really old stock- they were already 40 plus years old when I acquired them. I kept then stacked on top of one another until the reorganization.

The 2 on the far right- the right panel is the effect of both sunlight exposure (10-12 hours) and oxidation (you can also see the natural color traces from the stickers). You can see the color difference with the left panel as it is more vivid in color.

A little warning- I have both air dried and air dried/kiln dried pernies. Do not sun tan air dried pernies as it is susceptible to checking- didn’t have problem with the kiln dried and was stable. I only tried it several times as I wanted to see the effect of the color shift from yellow to orange. I have not tried it with the blood orange color pernambuco- those are very hard to come by and don’t want to gamble with the few stock I have left.

 

[Arn213]

Sure, but often one or the other dominates and for many woods, whichever one dominates, it does so very strongly in the first few hours or days after milling. In my experience, most woods that change color due to one or the other do so more from UV than from oxidization. Sycamore is a strong exception.

Agree- UV in the forefront it is like “fast food”. I filled this in with my response to Paolo.

 

[phinds]

Purpleheart seems to change fairly quickly, going from that beautiful deep purpley-red to grey. Faster in direct sun. So is that a combination UV and oxidation?

No, purpleheart SOMETIMES decreases in attractiveness, going usually to brown but just as often goes to deeper purple. There are quite a few species sold as "purpleheart" and there are different growing regions. See my page for further comments.

In all cases, I believe that UV effect predominates over oxidization.

EDIT: Also, you can change purpleheart to a deeper purple by baking it. Again, see my page.

 

[chatometry]

Thanks again everyone.
I will see if I can simulate (and accelerate) the effect with UV lamps, so that timescales become reasonable. That is, except purpleheart which changes very very quickly.

There are quite a few species sold as "purpleheart" and there are different growing regions. See my page for further comments.

So true. I find amazing pieces, but also boring pieces sometimes.

 

[phinds]

So true. I find amazing pieces, but also boring pieces sometimes.

What's MORE amazing to me is that sometimes the unattractive pieces become attractive and sometimes the attractive piece become unattractive. Damn things ought to be consistent, dammit !

 

[Gonzalodqa]

I agree with the Purpleheart comment. When freshly cut the color is very dull, after exposure the color becomes more vibrant. Not sure if it’s the light or the air though

 

[phinds]

I agree with the Purpleheart comment. When freshly cut the color is very dull, after exposure the color becomes more vibrant. Not sure if it’s the light or the air though

No, SOMETIMES it does that. Sometimes it goes from beautiful purple to dull brown. See my page. I seem to be repeating myself here.

 

[phinds]

By the way, it is also reported (I haven't yet checked it out) that white vinegar will turn purpleheart a more vibrant purple and even restore the color in faded pieces.

 

[chatometry]

Not sure if it’s the light or the air though

I had freshly planed boards in my (dark) lab for days - always brownish. Then I left then in sunlight for one afternoon and they got vibrant purple!
So whatever the air does, it does it very slowly w.r.t. sunlight. At least, for purpleheart...

 

[Nature Man]

I agree with the Purpleheart comment. When freshly cut the color is very dull, after exposure the color becomes more vibrant. Not sure if it’s the light or the air though

Very salient point about light vs air. Guess the only way to test this is either exposure to air in darkness, or exposure to light in a vacuum. Chuck

 

[phinds]

Very salient point about light vs air. Guess the only way to test this is either exposure to air in darkness, or exposure to light in a vacuum. Chuck

No, you can just put on a coat of shellac. That will block oxidation and do nothing to stop UV, so you don't need a vacuum.