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| Discoloration in Cuban Mahogany. WIll it oxidize out? http://luthiersforum.com/forum/viewtopic.php?f=10101&t=40051 |
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| Author: | Kent Chasson [ Sat Apr 13, 2013 6:49 pm ] |
| Post subject: | Discoloration in Cuban Mahogany. WIll it oxidize out? |
I just re-sawed some cuban I've had in the shop for a few years. The freshly planed outside surfaces (on the right) were uniform in color. Deeper in the board, there's streaking. I'm guessing air and UV exposure will even it out. Never seen anything quite like this though. Anyone have any experience? 
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| Author: | B. Howard [ Sat Apr 13, 2013 7:22 pm ] |
| Post subject: | Re: Discoloration in Cuban Mahogany. WIll it oxidize out? |
It will even out some in time, at least to the extent of what you show as the fresh planed outsides are. Just as you see the darker red and honey brown colored areas on those old faces you will see them on the new faces with time. The pattern will be different and looks as it will be more pronounced on the interior cuts. But hey, that's the natural beauty of wood. |
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| Author: | MikeyV [ Sun Apr 14, 2013 10:16 am ] |
| Post subject: | Re: Discoloration in Cuban Mahogany. WIll it oxidize out? |
I think it looks nice. You can sell them all to me. 
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| Author: | Kent Chasson [ Sun Apr 14, 2013 11:15 am ] |
| Post subject: | Re: Discoloration in Cuban Mahogany. WIll it oxidize out? |
The pictures don't quite do it justice, either the good or the bad. The uneven color on the outer piece is polarization due to runout from interlocking grain. The actual color is pretty even. The splotchiness on the interior shows no rhyme or reason but the dark spots are about the same color as the outside so I'm assuming the lighter areas will darken to match. I just thought someone might have seen this before. It is nice wood. There's a light curl throughout and it is amazingly stable. It didn't move at all as I sawed it. 10 slices without the slightest cupping or bowing. But sorry, Mikey. Not for sale at the moment 
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| Author: | Bobc [ Sun Apr 14, 2013 2:39 pm ] |
| Post subject: | Re: Discoloration in Cuban Mahogany. WIll it oxidize out? |
Kent I see this all the time. It will even out as the fresh cut surfaces oxidize. If you stack the sets it will take much longer. Stand them on edge so air and light hits all surfaces. |
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| Author: | Kent Chasson [ Sun Apr 14, 2013 2:57 pm ] |
| Post subject: | Re: Discoloration in Cuban Mahogany. WIll it oxidize out? |
Thanks, Bob. I was hoping you might chime in. I was pretty sure but I'll really relax now. |
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| Author: | AnthonyE [ Sun Apr 14, 2013 5:38 pm ] |
| Post subject: | Re: Discoloration in Cuban Mahogany. WIll it oxidize out? |
mmmmm... cuban mahogany is such a delightful wood. I would love to have a shelf full of it but is not that easy to get a hold of. It really is a dream wood in terms of workability and stability. There just isn't a nicer mahogany IMO. |
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| Author: | B. Howard [ Mon Apr 15, 2013 3:31 pm ] |
| Post subject: | Re: Discoloration in Cuban Mahogany. WIll it oxidize out? |
Kent Chasson wrote: The uneven color on the outer piece is polarization due to runout from interlocking grain. And that is what you are seeing on the fresh cut surfaces as well, Though I don't know anything about polarization in wood but it is caused by the reverses in the grain structure. |
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| Author: | Kent Chasson [ Tue Apr 16, 2013 2:38 pm ] |
| Post subject: | Re: Discoloration in Cuban Mahogany. WIll it oxidize out? |
Brian, I'm not sure it matters at this point but the color on the inside pieces is not from polarization. With polarization, the dark areas become the light areas as you change the angle of light. This is color in the wood from uneven oxidation and it looks the same from all angles. |
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| Author: | B. Howard [ Tue Apr 16, 2013 6:16 pm ] |
| Post subject: | Re: Discoloration in Cuban Mahogany. WIll it oxidize out? |
Kent Chasson wrote: Brian, I'm not sure it matters at this point but the color on the inside pieces is not from polarization. With polarization, the dark areas become the light areas as you change the angle of light. This is color in the wood from uneven oxidation and it looks the same from all angles. I have heard of polarizing sunglasses, but never wood. All I see in any of your pieces of wood is the change in direction of the grain from the twisting growth pattern of the Mahogany tree. It changes how it looks slightly as you rotate it. As you go from looking in the end of a series of cells to looking at the sides of them. But the figure can be seen and noted from any angle. If you stack the pieces back up in the orientation they were at before cut and leaf through them you can follow the pattern all the way through from the outside and see what I mean. I can see the pattern from the top piece on the left in your pic in the one on the right. It has shifted slightly by the way the tree has grown but there it is. |
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| Author: | Kent Chasson [ Tue Apr 16, 2013 7:02 pm ] |
| Post subject: | Re: Discoloration in Cuban Mahogany. WIll it oxidize out? |
B. Howard wrote: I have heard of polarizing sunglasses, but never wood. I'm not up on my physics and could well be wrong but my understanding is that the runout differentially reflects and partially polarizes the light. That's what's responsible for the light/dark halves you see in bookmatched tops with runout and for the 3D chatoyance in any wood figure. |
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| Author: | B. Howard [ Tue Apr 16, 2013 8:32 pm ] |
| Post subject: | Re: Discoloration in Cuban Mahogany. WIll it oxidize out? |
What you see IME is the orientation of the cells in the wood. See my little illustration. Here we have a slab of wood, the grey lines represent the cells in the wood, not the grain. The grain can be straight but if the cells are not parallel we have a condition called run out. The cells are generally little cylinder shapes, think small soda straws. As you see when we look at an angle from the right we are looking at the sides of the wood cells in the wood seeing nothing but fiber but when we look in from the left we are looking into the open ends ends seeing very little of the wood fiber. Most pieces of wood are not like my illustration, the cells run this way and then that way. This is causing the differences you see in your mahogany. The color changes are influenced by this feature and the way the cells hold the cast resin or dried tree sap within them. The resin is what seems to react with exposure and change color after being cut. This is also the underlying cellular structure that produces ribbon, tiger stripe, and quilted figures as well. When resawing figured woods you can see the figure shift as you cut it, every now and then I find a nice patch of birdseye in the middle of a vanilla board. Wood is amazing. So I don't know, maybe that is polarization? I learned what I know from the wood and it's not very smart....... Attachment: wood.png
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| Author: | Barry Daniels [ Wed Apr 17, 2013 8:01 am ] |
| Post subject: | Re: Discoloration in Cuban Mahogany. WIll it oxidize out? |
Its not polarization. Its simple reflection. |
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| Author: | mcgr40 [ Sat Apr 20, 2013 10:02 am ] |
| Post subject: | Re: Discoloration in Cuban Mahogany. WIll it oxidize out? |
This is exactly like every piece I have ever cut. I am almost certain it is oxidation, and the ribbony grain has caused the interior of the board to oxidize like that. I guarantee that to be fine, and have a chatoyance impossible to capture with a photograph. It will look "normal" in a few months left to its own devices. It will become fabulous with passing years. |
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