Neat texture, I wonder what would happen if it were stabilized?
You can't stabilize cork, it ain't work, I have already tried...!
With the CA finish, what seems to be the hardening of the cork, is no more than a built up of a hard crust over the cork material, it works only because the CA sticks to the cork but being soaked by it, not a chance...!
There is no other way to finish the cork on a pen, is that or either natural but that, wouldn't last long, dirt would make it ugly and bits of cork could be fairly easy ripped from the tube, the CA keeps it all together and protects the surface quite nicely until, something with an edge hits the pen barrel, the cork will flex back but the CA will shatter/crack...!
I work a lot with cork and that is a chance/risk that I'm willing to take...!:wink::biggrin:
Cheers
George