Buckthorn Berry Green Ink (Sap Green)

Since I occasionally do painting on my spare time, I was interested in the history behind the color sap green and how it got its name. It appears that sap green paint was originally made from buckthorn berries and varied in color depending on the ripeness of the berries. So far, I have only found one source documenting the process of making genuine sap green paint or ink from buckthorn berries: (https://medieval-whimsies.blogspot.com/2013/09/sap-green-from-buckthorn-berries-part-1.html). Currently, all modern paints labeled sap green are only a mixture of other pigments and contain no actual buckthorn berry juice. Given the historical use of the berries as an ink or painting pigment, I am wondering if the berries could also be used as a green dye for yarn with the right mordant.

Good question! Obviously there's pigment there, so the question is whether than pigment will bond to fibers (animal or vegetable) without mordant (a substantive dye), require the use of a mordant (and then the question becomes which one), or not at all. And even if it dyes fiber, will the color be light and wash fast or be fugitive and fade quickly as many berry dyes do....

I don't have rhamnus/buckthorn growing on my property here in north central Ohio, or I'd give it a try....