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I recently saw an interesting microscope photo in an endgrain slice of spruce, nicely showing the structure. To my surprise, this was visible with a good magnifier too, and even through a "supermacro" photo. Subsequently I could take a couple macro photos trough the magnifier, getting even closer.

They could have looked a lot better if the wood was cut cleaner. I used a well sharpened knife but the key is to cut thin and slow, but I still pushed too quickly.


You can see that the "grain lines" have pretty much the same cellular structure as the fast growth, just that they are packed tightly and the cells appear to be closed. I suspect there is a high content of resin in the area, which gives the dark color and "cements" it. We all know how it feels to press a nail in a dark line (doesn't really work, but in between, it goes all the way down).

Each dark line seems to act as a brace then.

I am wondering whether the fast growth areas correspond to the spring period when the tree produces new needles?

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Build log

Hi Alexandru,

Nice photos. I have seen line drawings of the cell structure of spruce, these are the only photos of it I've seen. I have heard that the grain lines act like internal braces. However, I have also heard that spruce can be stiffer with the grain lines parallel to the glued edge. Go figure. I have seen photos of Torres guitars with grain lines in the harmonic bars parallel to the top.

Thanks for the picures.

Max

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Max Bishop
Brighton, Michigan

Thanks. Well. harmonic bars have lots of height. I don't think grain orientation matters a whole lot in getting sufficient stiffness for them. But for the soundboard in itself, or a flat fan brace, i would still stick to quartersawn

Edit: I just did a deflection test on a 6x6mm brace, which had 2 dark lines. Same result.

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Build log

Neat photo Alex!

It's neat that you can see an abrupt, well defined line on one side of the drak grain line which appears to be the transition from winter to spring. I couldn't really tell where spring ends and summer begins. Then you start to see a long transition from fast growth, light colored wood to slow growth, dark colored wood which I assume is fall growth. It does appear you can see a transition line between fall and winter growth where the dark line becomes solid.........which I'm guessing is when the temp drops below freezing and stays frozen for the winter.

Thanks for posting those pictures.

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Formerly known as Adaboy.......

Alex: Real nice photos and interesting. Thanks for showing us. For those interested Bruce Hoadley has a couple of books on wood. One called "Understanding Wood" and the other "Wood Identification".
Tom

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A person who has never made a mistake has never made anything!!!

So, with all of this elegant microscopic structure, why do so many consider that obliterating most of it with a layer of nomex (etc.) is the way to go?

BTW, the harmonic bars in my Hernandez Y Aguado are also grain parallel to the top.

Daryl's right: the wood starts off in the spring when there's lots of water and grows fast, with large cells that have thin walls. As the season progresses growth slows, the cells become smaller, and the walls are thicker, making the wood darker. Eventually the tree goes dormant, and growth stops until next spring, when it starts in with large thin-walled cells again. You can always tell which is the 'bark' side.

Wood is stiffer and has less shrinkage in the cross grain direction if the annual ring lines are perpendicular to the face, as in your shots. The medullary rays, those light croswise lines, which are small bundles of cells running acros the grain, tie things together.

It's pretty amazing what you can do with a digital camera these days.