There’s a lot of fiddle wood that I inherited from my father. These 2 plates were both rejected, for different reasons. The Maple back was narrow with a couple of saw cuts intruding into the required area. The Spruce top is thin, and wasn’t glued very well – there were gaps in awkward places.
I succeeded in separating the Spruce by applying quite a bit of hot water to the seam and wedging it apart. There was only a bit of wood damage. A bit of hand planing made the surfaces clean and consistent. They glued back together with no obvious gaps. There’s still a hand-written note “crack”, which is a dark line within one of the half-plates, near the peak. I suspect that once the plate is formed for the arches the level will below that mark. I’m not convinced it’s a crack.
The Maple plate was more problematic. It wouldn’t come apart, even with lots of hot water and wedges at both ends. I ended up band-sawing it apart. I inserted a Walnut centre. It’s plenty wide enough now, even with the saw cuts. “It’s not a bug, it’s a feature!”