Alexandre Saint Pierre's Calligraphy with Yellow ink from Buckthorn.

Yellow ink from green buckthorn berries:

Alexandre Saint Pierre mixes ink by mixing a drop of gum arabic and one of distilled water (DW) into treated and dried buckthorn juice.

He then paints it onto the end of a goose feather quill that he's cut.

He writes,
"a good yellow for writing made from
     buckthorn... this test with equal
     parts distilled and gum water.

     this test with only distilled water

     above are from buckthorne ink dried
     in shells, this test is from juice in
     a glass jar that has never dried"

The only part that's not quite right is that with the DW only test it should have been watered further to produce yellow rather than brown and in the jar the juice in the jar had been partially dehydrated.

The shells have been sealed in plastic sandwich bags and the jar has been lidded.  Stay tuned for further developments and experiments.