Color change in buckthorn with gloss poly

[GB]

I brushed on gloss polyurethane to seal this buckthorn stave a few weeks ago and it's had a dramatic color change.  I really like it, but I'm wondering how and why it turned out this way.  Just a reaction from the chemicals in the poly?  The other staves I sealed with shellac have the uniform amber tint, with none of the red and gray like this one.
This is the sapwood.  Peeled the bark off and sealed it.

[wizardgoat]

Cool. I have a stave of this stuff, it's really pretty wood

[Badly Bent]

Not sure what you have going on there to get the different colors but I've seen a fair amount of variation in different staves of the buckthorn I have here. One thing I have noticed is If I let one season for months with the bark on the sapwood will be dark and have variations in the color along the surface after I remove the bark. If I strip the bark off a stave just after cutting the tree and then seal it right away it will usually just remain a typical white sapwood color.
Also though I'll mention that I've had some issues with sapwood rot on some staves that season with the bark on which has caused some tension failure at the backs. Because of that I've been stripping the bark and sealing the backs right from the start recently on my buckthorn. None of this probably applies to what you have going on with yours, just thinking aloud I guess.

[GB]

I peeled the bark off this one and sealed it right away.  I remember Cody saying the same thing about the sapwood breaking down over time if it seasoned with the bark on.  It is possible that this one took in some sunlight from one of my basement windows.  The ones I shellacked didn't.  Oh well, it's a mystery.

[bjrogg]

That is really pretty colors. I'm really not sure what Buckthorn is. I've been wondering about what we call Thorn Apple. It has a bark very similar to Hop Hornbeam loves to grow in fence rows where it grows short and I gnarly has very sharp 2-3" thorns and little round fruits. In our woods it grows quite straight and tall. Is this the same tree?

[PatM]

 They are  different trees.  Thornapple is also called Hawthorn.

[bjrogg]

I noticed that Pat when I looked them up on e-net. Do you know if thorn Apple would make good bow wood? Sorry GB I should probably start deferent thread for this.

[PatM]

I've never had access to a decent piece but it is very highly regarded by those who have.

[PEARL DRUMS]

I'm sure it would BJ. Most all fruit/mast trees are.

[bjrogg]

Thank Pearl it always seems like some springy stuff might have to get the heavy leather gloves I hate getting them thorns stuck in hand takes forever for that to get right again