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One of the boys sent the attached over... 1970 00-18 with high action due to separated neck dovetail. Once the extension was released, the neck popped out without further effort. The white material is multi-ply posterboard that appears to have sheared down the thickness of the cardboard. Posterboard comes in various thicknesses, so apparently the temptation to use it versus veneer for dovetail shim stock was irresistible, despite it being treated to have less ability to absorb glue or moisture. Most busy repair shops will have seen cardboard or paper used for shim, but they will also have seen why that shim material can be less than ideal.

This was not a Martin factory initial set, as the neck shows clear evidence of a reset, as well as installation of an oversized factory bridge and .156" width saddle to address intonation issues. Given the bridge is a Martin oversized article, I suspect the reset was done under warranty out in the field. Still an unfortunate choice of materials and poor workmanship.

So the glue worked, but the substrate was a really poor choice.

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"Act your age, not your shoe size" - Prince

The posterboard stuck to the wood surfaces well. It just doesn’t have any internal strength so it separated easily. That might be good for temporarily holding some shell for cutting out an inlay but not for a more permanent joint.