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So I have seen this on few of the Taylor, Larrivees as well as few custom guitar lately.

The end block on the lower bout is showing through the glare on the top wood. It's minor but I can clearly make the block through the top wood...sort of like two stripes or skinny lines. I'm guessing the block not being flush with the side will cause this but what else? Is there no way around this since even if builder flushed it perfect, humidity will get the guitar to show this???

How do you guys make sure this doesn't happen with your guitar?

Sanding well with the radius dish helps. Additionally I chamfer the edge of the tail block so the gluing surface is only as wide as the kerfed lining.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Not for this reason, but I always chamfer the tailblock top so that it is only as wide as the linings where it is glued to the top.
I just think rightly or wrongly that vibration in the area is going to be freer without the block protruding.

I can't say that I have ever noticed the end block perimiter leaving a visible tatel tell image on the top of back of any of my guitars.

Its not even always humidity that causes this .. the forward rotational torque of the bridge causes the top behind the bridge (and all the way to the tail block) to be pulled slightly upward - if the tail block is wider than the kerfed lining - then over time this will start to show. Simple fix ... taper the top/bottom of the block to the lining width before putting the top/back on.

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Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

Sounds like a case of extreme dryness for the guitars concerned.

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Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

So would this cause the guitar to crack down the line? I guess it depends,huh?

It's just interesting to see such a reputable companies or builder either not know about the fix before the top is put on or don't think it's important enough to address...


btw, Tony, tapering sounds like a great idea.

This is not uncommon whether due to changes in environmental conditions or as a result of stresses on the top, or some combination of the two. Many people also thin the outer edge the soundboard as part of their tuning process, making it even more apparent. The solution, as others have pointed out, is to bevel the top of the block so that it is the same width as the kerfing.

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Randy Muth
RS Muth Guitars Website
RS Muth Guitars Blog
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In the worst case, the block may have the grain oriented perpedicular to the side grain. This will not shrink at the same rate as the sides. Sometimes plywood (even home made laminate) can do this, too. It can be a worse problem if the heel is made with the grain the wrong way, in which case a hump will develop in the fret board. I have a rather expensive and otherwise good flamenco that developed this and needed the fretboard leveled, after which it seems stable enough to not cause more problems. Some of this is due to lower humidity during storage than construction, but really, you should not have to deal with this.