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The recent discussion about runout in bracewood got me thinking about runout in spruce tops, and how to identify it, something I have always wanted to understand better. It’s a topic about which I’ve seen very little discussion. I’ve always assumed that’s because runout is more difficult to ID in the relatively thin top plates.

Can anyone offer any insight into a reliable way to spot runout in a raw spruce top? For example, if you’re sorting though a stack of nice tops, tapping and flexing them, and you find one that meets all your criteria of stiffness and musicality, how do know whether it has significant runout?

Sometimes you can see the runout in tops by holding them in front of you and noticing the way the light reflects on the tops. If one side looks dark and the other side looks light then you may have some runout. I don't know a better way to explain it but someone will come along and be able to!! Ha.

most sawed tops will have run out . Look for split stock . Higher end top that are split will be a higher grade . $400 on red spruce is pretty common . Sitka can run up to $150 . It takes a lot more work for splits . After all the years working on these things I have heard some killer guitars that had a lot of run out .

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Sometimes you can see the way it reflects light, like SammySam mentioned. When comparing both bookmatched halves side by side the runout will be going different directions. One piece will look lighter or darker than the other. You can amplify the effect by wetting it with naphtha or some kind of thinner.

Another method, and what I believe is the best method if the piece is big enough to allow is to take a plane, and cut both directions. If it's easy to cut one direction, but the plane digs in and trys to lift chunks the other direction it's got runout.

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I didn't mean to say it, but I meant what I said.
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Thanks for the tip woody b

Id be curious to know what you'd do .....if you had a piano soundboard /bookmatched thicknessed plates
and wanted to check for runout using this method .

would you plane rows to(the boards width) of single continous shavings
and then rotate the board and repeat

And if your plane sunk /tore out how close would you want to get to that runout
if you had enough wood left for say a bouzouki or whatever

Is this depending on the severeity of tear out you get ?
tomas

I have visited several tonewood cutters & all of them sawed their tops from hand split billets.
This is the industry standard, as far as I can tell.
The problem arises when the tree grows with a twist. This is very common in most species of spruce, Engelmann probably being most prone.
Large companies need to keep their people working & will sometimes buy logs with a twist, if "perfect" logs are not available.
IME, if you can see a definite colour shift at the joint, the runout is fairly extreme.
Usually, you can see evidence of runout along the edges of the board, where subtle lines in the wood don't run parallel to the face.
If that doesn't work, try this... If the top has some extra width, rip off a narrow strip, hold it at the ends & bend it 'till it breaks. If the runout is significant, the piece will usually break along a grain line, which will show you exactly how much runout is present.
The other way I use is a bit harder to explain, but I'll give it a try...
Stack the two plates in their bookmatched position & examine the end grain for any angle off 90 degrees. If the boards appear well quartered on both ends, you probably have minimal runout.
If one end is good & the other shows off quarter, you will have some runout. The further away from vertical, the more runout there is.
If the grain is off vertical at both ends the boards were poorly cut, or there is significant runout.
To determine which is the case, this check will tell the tale.
Look at the end grain on one end, then flip it end for end & examine the grain on the other end. If the angles both go in the same direction, you have runout. If the angles reverse,(and are about the same degree off vertical) the boards were simply cut off the quarter. The greater the divergence, the more runout is present.
I hope this makes sense...
And John is perfectly right... There are some killer guitars out there with serious runout in the soundboards.

One of the points of the bracewood runout thread was that the grain can be perfectly vertical both ends and still have invisible runout.
The argument against invisible runout is not a tonal issue, but a strength issue. Tops with invisible runout are weaker than tops without it, and are more likely to distort unreasonably over time.

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Old growth, shmold growth!

Sometimes you can rub a piece of high tack masking tape on a top and pull it off. It will show the direction of the runout by the way the slivers come off.

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Ken Franklin
clumsy yet persistent
https://www.kenfranklinukulele.com

Sammysam – welcome to the forum!

Daniel – thanks for the info on examining the end grain. That’s something I was totally unaware of, but it makes sense.

Thanks to everyone for the replies. It sounds like there really isn’t an idiot-proof method to identify runout when sorting through a supplier’s stacks of tops. I’ll start paying more attention to the subtle grain lines on edges, and comparing how light reflects from the two sides.

I like to use this technique when I'm removing the tape after binding. It serves two purposes: calibrating the runout in my top plates, and determining how much I should thin the edges of the top. I call this procedure "tape voicing". (It's patented, so be careful how you pull your tape.)

When I don't have the luxury of building a guitar to measure runout, I cheat. A 40 or 50 power pocket microscope shows up the runout on the invisible face. I don't think they still sell the model I have, but McMaster part #1452T54 is close.

Ken-I really like your idea of using the tape before you build the guitar. I'll have to try that.

I understand that some run out is okay, nothing is perfect.
I'm sure that at some point you can have too much run out.
Will we run into structure or sound problems first?

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Say what you do, Do what you say.

I've worked on a lot of cheap guitars. A guitar store that I used to work for frequently bought for his cost $80 solid wood acoustics 30 or 40 at a time and I would have to go through and set them all up. A lot of the tops had extremely severe invisible runout, to the point of being several shades darker even face on to the soundboard. many of them already had top distortions, belly bulges and potato chip soundholes, to some degree, even being brand new, so I would frequently inspect the interior for loose braces and other problems.
As the guitars were braced pretty standardly and the tops were all the right thickness, I always attributed the fact that they distorted so easily to the inherrant weakness of the slanted grain caused by severe invisible runout. Many of them frequently had off vertical grain as well, but but I've seen plenty of guitars with off vertical grain that were still undistorted. I suspect they were not made from split billets.
I bought one and worked it over, replacing the frets with stainless steel, cutting ahole in the side and intalling a sidemount preamp, replacing the nut and saddle with bone, and took pictures of all the processes for my web page. After two years the bridge popped off and had to be reshaped to the soundboard and reglued.
Most of them still had good tone, and we were able to sell them to beginners for a little over a hundred bucks. We went through one or two batches a year for a few years until the company stopped making them.

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Old growth, shmold growth!

Some makers of high end classicals don’t mind a little runout.



Joe

I suspect most of us here build by feel/deflection. I cull the weak stuff, which may or may not have a bunch of runout. I do believe it's really important to understands a clients expectations reguarding runout.

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I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

Not only just by looking for a light and dark half (which is applicable) but if you reflect the light while raking the light up and down on the board if there is little or no runout the light will be continuous across the board. A top with runout the light reflections will be offset. Hard to explain exactly what I mean.

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John Mayes
http://www.mayesluthier.com

Thanks for that, John. So when you do that are you holding the top horizontally with the end grain in your hands, and tilt it side to side to change the reflection?

This is the technique I use to detect runout in rough sawn or unfinished tops. I hold the two halves in the same plane, just as they would be after joining. I view the wood with a long fluorescent light, oriented left-to-right, perpendicular to the grain in the top. Under this line source of light, the dark/light of the two halves becomes much more visible, almost as when the wood is finished. There will be crosswise bands of reflected light on each half, and if there is runout, the bands will be offset (staggered) on the two halves.
In addition, the 'band' of reflected light will tell how much spiral the tree had. If it tracks across the top perpendicular to the grain, then the tree had little spiral. But if the reflected band is at another angle, then the tree had spiral, and there will only be one place on the width of the top with zero runout.

The key component is width. As the board gets wider, the tilting of the grain on the ends of the board of spiral grown wood becomes much more pronounced. Most of the red spruce bracewood I have cut is less than 4" wide.
If you have a spiral tree (most red spruce has at least some spiral), then you have the choice of maintaining perfectly vertical grain and have runout everywhere except the heart (sawn logs), or you can cut split billets, placing the zero runout at the bark edge, where most tops are joined. In the latter case, the grain can be vertical along the joining edge, but it will not be vertical on the outer corners of the top. IMHO, this is no downside, since the tops cut this way will not show dark/light on either side of the center joint, and the strongest, most vertical grain will be under the bridge.

At least one of the major cutters of red spruce does not cut from split billets.

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John

John explained much better what I essentially do.

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John Mayes
http://www.mayesluthier.com

It is easiest to identify runout in tops when they are not sanded/planed. In a "raw" top you will see the direction of the grain by looking at the "fuzzy hair" of the grain so that the runout in each half is easier to see. Likewise if you have seen raw tops in which the hairiness of the grain along the edge is long...look closer and you will see it is long grain of a top that while from the end it looks straight grained is actually runout. If you pull on those long strands you will see they run into the top whereas a split top would look rough but not have hairy grain along the edge.

When David LaPlant. Joshua French and others took part in Jose Romanillos' classes in Spain, Jose required you to bring your tops in the raw before then telling you which of the tops you brought was the better top to use. Once people started to see that tight grain could be compression grain and that runout could be seen by a stringy edge, the message was that guitars with long continious grain resonate longer and have better sustain and that for classical guitars every element working optimally can make a difference.

A top bought from a dealer that is sanded and looks great can be full of runout or could be a great top but most of the visual clues are gone.

Thanks guys for your knowledge, im gonna have to read this a few times

I think this would make a great luthier tips du jour video

This is very interesting. Could you post a picture of the fuzzy hair along the edge that you are talking about? I think that would be extremely helpful.
Thanks in advance.

Tony

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http://www.CostaGuitars.com
PMoMC

Wow, this is some great information! Thanks for sharing this info, guys.

thanks for the info, a much interesting read.

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member of the guild of professional dilettantes

Yeah, this is one thread that I'll have to read several times to grasp... Got to go look at some tops.

The best examples of a ragged edge from a top that was cut in a way that there is alot of runout are on eBay. While a top can show vertical grain from the end and look like it is radially sawn, it can be in fact out of plane and this is what happens with many sawn tops. There are tops on eBay that are for sale that on the face look okay but when you look at the inner edge of the two halves, you will see a long stringy fringe that is so visible that it is obvious.

I am not talking about the typical rough splintery edges and fur on the face of a cut piece of tonewood but rather runout that shows. Once you see the edge you will recognize it. It is not just one seller but I dont want to mention names.