This is black walnut ink I made about 6 months ago from the green skins of the black walnuts and amber mouthwash.
First I boiled the black walnuts and removed the now black skin from them and used a potato masher to further extract the colour.
Then I strained the ink into bottles, then added 1:1 amber mouthwash to prevent any mold or bacteria growing.
And waited for the mixture to condense over time.
I use the ink by refilling the cartridge of a fountain pen with a small dropper, but it could be used in a lot of different art projects as dye, ink or paint. Mine will need a final strain through a fine mesh sieve or a cloth.