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I have a very nice sitka spruce top from LMI. Grain is tight, even and straight. But there is obvious runout in the top. When the halves are bookmatched, you can see the color difference due to the interaction of the runout with the light (I hope the pictures uploaded correctly).

I am considering flipping one side so the runout color matches. This would mean the top is not bookmatched. The grain is so even across the top that I believe it would still appear to be symmetrical.

Any structural reason to keep the bookmatch, and accept the color mismatch?

It's been done before. I would say the only time you might not want to do that for structural reasons is if the annular rings go off vertical towards one side. Otherwise go for it. BTW LMI would take that back and send you another one if you really wanted.

The only problem is that LMI will return it and send you another one exactly like that -- runout is prevalent in the vast majority of tops and finding tops without any runout is always difficult. I would not reverse the tops as you have (I would always want a perfect bookmatch) - instead, see how the top looks with the "outsides" in the center. You may need to remove a bit of material from your new "center" but chances are the runout might be a lot less if you join the top that way. Always check that other orientation and see if it helps with the runout. Sometimes it's a compromise as the grain might not be as attractive in that orientation.

I do the outside as the center thing often enough myself.

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Brian

You never know what you are capable of until you actually try.

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As others have stated I will check the run out on both edges of the top and join the edges with the least run out rather than considering the width of the grain as some do. The bridge adds a fair amount of stiffness so even if the wide grain is in the center I think it can still make a good sounding top.
Runout does affect the tops ability to hold a bridge and is a reason to avoid extreme runout on instruments with glued bridges. If you have ever seen a lifted bridge where there are soundboard fibers on one half but not the other this is usually because the top has runout. If you do go with a "slip match" you may want to orient the runout so it "rises" toward the neck so a lifting bridge will be less likely to tear out the grain (and one reason to use a slip match on a top with evenly spaced grain but significant runout)
If a top has a lot of runout I try to not use it for an instrument with a glued bridge (and in extreme cases, not use it at all)
Have you measured the run out on the soundboard or are you just going by visual cues?

What is the "outsides?" Are you saying that you can tell from wood milled like that that you know which edge is toward the pith and witch edge is towards the bark?

If you have uneven width grain I have read that the wider grain lines are generally toward the pith and the tighter grain is usually toward the bark.
I think many luthiers usually put the tight grain to the center ("inside") and the wide grain to the "outside" so there are opposite meanings that are used colloquially.

In fact, you can tell quite easily if you understand the way wood is laid down. The transition from early wood to late wood during the growing season is more gradual than that between the latewood and the earlywood of the next season. This is most easily seen on the end grain (and with a magnifier). You only need a single clear ring to confirm direction to pith and bark. (I’ve analyzed thousands of spruce cores in my career, so this likely more obvious to me than most.)

When joining plates, it’s usually advised to use the book matched edges that minimize runout along the centre seam. In the OP’s case, the runout seen by colour differences seems rather pronounced and uniform on both edges — so much so that I wonder if the colour differences are due to surface UV exposure rather than runout.


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This is off topic, kinda, and I don’t mean to steal a thread, but shouldn’t the grain lines closes together go toward the center? That my immediate thought ... then I think... we’re always making the outside at the rims stiffer so..... why do we put the close grain to the center anyway? Wouldn’t it work better w the outside in the middle?


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Ideally you want the stiffest part of the soundboard to be in the middle. This is probably more important for lutes and classical guitars that have light thin soundboards. For steel string guitars it seems to be less critical and some of the best makers have joined tops with the wide grain in the middle. I like to join steel string tops so the edges with the least amount of runout are in the middle. I think this helps them retain their bridges better. Lifting bridges seems to be a more common problem for steel string guitars than it is for classicals.

Cool I didn't know that! Learn something every day. Pretty much all of the Sitka I have ever had is uniform across. The trees are so huge my guess is that's not hard to accomplish. It seems of all the spruces too that Sitka is the one that has the least runout. Carpathian on the other had seems to have runout regularly.

Didn't, or perhaps even still today, Martin actually put the wider grain in the middle? I never understood the logic in that myself. A lot of luthiers, myself included, even go as far as to thin out the perimeter of the lower bout for that very reason. But hey what ever works.

Joining tops on the edges with the least runout also helps with cosmetics, and in a market place where cosmetics seem to be as important as the sound of the instrument it can make a difference. If the runout is similar on both edges of the top I prefer to put the tighter grain in the center. I also do perimeter sanding as the final "tuning" of the top.
I don't know what Martin's thinking was, or if there was any consideration given as to which edges of the tops were glued together. At one time I think they used a "windmill press" to glue up tops so it was probably a quick choice as to what edges were glued together.

Isn't the runout that causes the color differences caused by the way the grain RUNS, and not the orientation of how perpendicular the winter/summer grain lines are? Strong runout (viewed from the side) is independent of how close to 90 degrees the grain (viewed from the end) seems to be. It will weaken a board, and it the case of a set already cut, you might as well make it LOOK even if the board can be flipped to make it dark/dark, light/light; and not light/dark.

But then curly wood will run both ways several times along the length of a top or back. I always think of it as a spring. Maybe you can leave it thicker, and still get the movement that you want. I really don't know. I don't have any idea how much it would affect the north/south strength.

Wood is usually only graded by looks first. Then how well it it quartered. I did find one place that measures the speed of sound in the wood. Not a whole lot of difference, but they can't really put duds up for sale then, can they? Anyone else can give you duds.

I've never seen any place that gives you the grain runout in degrees. Unless you're picking them out in person, or buying wood that is split, how would you know?

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Why be normal?

Some trees grow with varying degrees of spiral twist. Because of this you can have different amounts of runout from one edge of a soundboard half to the other. With book matched pieces you can measure the runout and match up the edges that have the least runout.
This can help with the cosmetic issue some. Often both edges have some runout, so it is a matter of choosing the lesser of two evils.
Here is an article that explains spiral growth in trees:

http://www.logbuilding.org/SpiralGrain.LBN63.pdf

I’m not sure that there’s correlation between tightness of grain and stiffness...

Take a chisel, pry up a bit on the corner, and see if it splits straight, or on an angle.
In the future, if you are concerned, buy a hand split top.
Alan

If you are talking about the stiffness of different tops I would agree - tighter grain doesn't always mean the top will be stiffer. If you are talking about the grain within the same piece of wood, the tighter grained sections will generally be denser and stiffer than the wider grained sections. Having a piece with even grain may be desirable in this respect.

Good photography will show it. Check out A.Hix Tonewood up in the sponsors, his soundboard photos have the correct lighting setup.

As Clay says, spiral twist will result in some runout on one or both edges even in split wood.

As a full time soundboard producer for 24 years, I can tell you how we at alaska Specialty woods does it. Nearly every tree has some twist. And even the trees that are over 4’ diameter. But the field/s we slice into tops will only have a fraction of the slope of the overall tree. And trees with offset hearts will have more grain slope in the quadrant with the least amount of “Meat”. Anyway after primary breakdown of log into block. We slice the block crowding the edge that would yeild the prettiest tops in regards to color and texture. Since it’s ultimately the consumer[people who buy guitars] that buys with their eyes, that kinda drives “grading” criteria.. Anyway, by crowding whatever amount of grainslope is in the fiber to the joing edge, the “flash” or “black/white syndrome” , the reflection/refraction of light to the fiber is diminished. And the important tonal properties and strength is maintained at the center and joining edge of the soundboard. It’s my opinion that it doesn’t matter whether wether boards are joined on looser or tighter texture grain. Sound is produced by vibrating boards moving air. Looks are, just looks. Regarding your question of flipping one of the boards to diminish the flash.. That is an excellent solution to the appearance, and elimination of the “flash” caused by the reflecting/refracting fibers right next to each other. This option is something that one can do with some booksets of non-figured tops, but certainly not figured tops, as there would be absolutely no symmetry at all. Back to cutting tops. Some soundboard producers Just cut boards as easy, and with little thought but “cut boards” and some go for strictly the highest quantity of yield. And both ways, end up to sort things out at the grading table by strictly looks. I have been to many soundboard producing shops in North America and Europe. ASW has perfected dissection of log into soundboards as an Art. And an art that focuses on the highest structural, tonal and aesthetic attributes that any section of wood will yield.

If it was me I'd keep the set and join it as shown in the first picture. It works for me.

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Joe Beaver
Maker of Sawdust

Many of those red spruce tops were only jointed on one edge, so the decision was already made before putting them in the press.
I think I know why Martin tended to reverse join tops in the old days. There are plenty of reasons not to. The bark edge is usually clearer of defects, and the grain tighter and more vertical, since the radius of the growth rings is greater. But I am convinced that Martin was buying tops that were cut from long logs, and those tops from spiral growth trees would have the most runout on the bark edge. By joining the heart edge, they were reducing visible runout. In many cases, that meant less vertical grain in the center, as well as including defects like pin knot shadows. In some cases, those defects could be placed in the soundhole or under the fingerboard. Still, it is much easier to avoid defects on the outside of the pattern.

As a 30+ year veteran of cutting red spruce, I always cut from split billets, sawing parallel to the split on the bark edge. As a result, there will be no visible runout when joining that edge, and any runout or slight off-quarter will be relegated to the outside edge of the tops.

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John

From the original post, I'm thinking you want to know if flipping 1/2 of the "bookmatch" will cause any problems. If you flip half of it you will have a top with two grain directions. I'm pretty sure I've done this in the past any didn't really know if there would have been a difference in sound after the guitar was constructed. Actually, I wouldn't know how you would tell.

I'll note that ring spacing does not make any systematic difference in the stiffness of the wood, either along or across the grain, so far as I can tell from my measurements of tops, so long as the wood is equally well quartered and has no run out. Off quarter costs in cross grain stiffness, and run out reduces long grain Young's modulus. Because of the larger radius to the outside of the tree it's usually easier to get the bark side to be well quartered, but a lot depends on the tree and the sawyer.

As Tim Mullin says, once you think about the way trees grow it's easy to see which is the 'heart' side and which is the 'bark'.

It's not uncommon for trees to grow with different amounts of twist at different times. You will often see tops that have almost no run out on the 'heart' side, and the run out increases toward the 'bark'. A bark side join will show a lot of 'flash', where a heart match will have none to speak of along the joint line. The run out is still there, of course, out in the wings of the top, but most folks wont notice that. More to the point, you get to glue the bridge down on a spot that has little or no run out, which will save a world of problems later.

There is no spiral in the heart of a tree. By 'heart' I mean the initial growth, or the center of the growth rings. While spiral can increase or decrease through the life of the tree due to growing conditions, in general, it tends to increase as the tree ages. And on a tree with an offset heart, the spiral will tend to be greater on the short side. When selecting red spruce trees or logs, the maximum amount of spiral we would accept was 2" in two feet, or a slope of 1/12. Anything less than 1/2" (1/48 slope) was considered exceptional, and a tree with no spiral exceedingly rare and coveted. Certain areas tended to produce trees with less spiral, and the few old growth trees we encountered seemed to have more, on average.

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John

I hesitate to correct this, but the picture presented my John is not supported by the literature. There is indeed no grain angle at the pith, but then we generally find left-handed grain angle (by convention expressed as ° greater than zero) rapidly increasing to a maximum at 5-20 rings from the pith, then decreasing gradually and in older trees and becoming right-handed (negative). For sawn structural timber, it is the left-handed spiral grain in the corewood (“heart” is not defined by age or size) that causes the most grief through warping. For tonewood produced from larger stems, the spiral grain of concern is primarily negative grain angle further from the pith. Fortunately, the change in grain angle generally slows down at older ages so that the producer can minimize the difference (and hence the grain runout) across the face of the plate. The challenge is greater with smaller (younger) stems.

As you can imagine, research on spiral grain development is difficult and we find the best data for intensively managed lumber species such as Norway spruce and radiata pine, where the emphasis has been on development of spiral grain (and other wood properties) in the corewood area. Information on spiral grain from large old-growth stems is much less extensive.


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