Active dye compound; Rhamnetin.
CI Natural Green 2
Our berries are 100% organic, foraged from the woods in Europe from Rhamnus cascara.
Use at 100-200% WOF
Soak in warm water for several hours before using, boil for at least 20 minutes, and filter the dye bath before adding wool or textiles. A full 19th century recipe can be found below. 
 
Buckthorn berries are also known as Avignon berries and Persian berries, common buckthorn. The color is mentioned as sap green I and II, bladder green (because the concentrated juice would be stored in a pigs bladder), and juice green.
 
Buckthorn berries give a great lightfast yellow to yellow-green. 
 
These berries are a substantive dye, so no mordant is needed on wool, but mordants will improve light fastness and alter shades. Different Ph levels will create different colors.
 
Buckthorn berries were used in green ink making in medieval recipes, and many traditional dye recipes in the 18th century. The dye was first mentioned in the 15th century Nürnberger Kunstbuch and the 16th century Plichto. Fun fact: in old EUropean folk cultures, buckthorn berries were not only used as a purgatory, they were believed to help ward off witches and demons.
 
Two recipes for a sort of ink or dye from 1846 by Johann C. Leuchs:
1. The half-ripe berries are crushed, fermented in the cellar, pressed and mixed with alum (or half alum, half potash).
The juice is then boiled down over a low fire to the thickness of honey.
Color stability can be increased by boiling the berries in vinegar.
The light fastness and the intensity of the color can be improved by adding verdigris (copper sulfate). This triggers a chemical reaction between the dye in the buckthorn berries and the copper in the verdigris.
2. The berries are boiled with water to a pulp, strained through a flannel cloth, and then evaporated to an extract.
Then add 1/16 alum, continue to evaporate and finally fill the porridge into veal, beef or pork bladders to dry.
Lye is added to the bubble or sap green, which causes the green to turn yellow. If the hue remains green, the lake is called bladder green.
 
For pigment production: To produce a green lake (a pigment) for oil painting, you can first mix the juice with alum and then slowly add potash lye so that a precipitate forms. This dried color lake can be used in oil and other carriers for painting
 
 
Learn here how to make ink. Learn all about Persian berries here.