Well everyone here seems to have different experiences from leaving sapwood on?
I've left it on many summer cut staves and had no problems. BUT it took me a while to figure it out.
If I cut a summer logs I split it into staves,then work one at a time,by peeling the bark off like a nanner. You can't seal it right away, there is too much surface moisture and your sealer will dry on top of it,no good. Let the stave set for an hour or two until it feels dry to the touch,then seal it with shelac.Make sure every coat dries before you lay on another. I use 4 coats.No problems.
oh, and make sure your shelac is good.If it don't dry within 5 mins, It's not gonna work on green wood.