Buckthorn lake and sap green are organic pigments prepared from the berries of dyer’s buckthorn (Rhamnus catharticus), also known as French, Avignon, or Persian berries. Ripe berries yield a green pigment known as sap green (verde di vesica, vert de vessie, bladder green), while unripe green berries produce a yellow lake (stil de grain, Dutch pink).
Two distinct preparations existed:
- Transparent juice used directly for washes and glazes in manuscript illumination,
- True lake pigment precipitated with alum and chalk or potassium carbonate for greater body and opacity.
Described in numerous medieval and Renaissance recipe books including the Segreti per Colori (early 15th century). The juice was boiled down, inspissated, and preserved in pig bladders (hence “bladder green” and “verde di vesica“). Combined with azurite or ultramarine to produce richer greens. Fugitive and prone to fading, especially in light exposure. Largely replaced by more stable synthetic greens by the 19th century.
Usage Timeline:
| Pigment | Prehistory <3000 BCE | Antiquity 3000 BCE–500 CE | Medieval 500–1400 CE | Early Modern 1400–1800 CE | Industrial 1800–1950 CE | Present 1950–today |
|---|---|---|---|---|---|---|
| Buckthorn Lake |
Key Properties:
| Properties: | Ripe berries: transparent deep green; Unripe berries: golden yellow; Juice: highly transparent, used for glazes; Lake: semi-transparent with more body; Moderate tinting strength; Fugitive (poor lightfastness) |
| Usage: | Medieval to 19th century (primarily 14th-18th century) |
| Source: | Organic/Plant |
| Toxicity: | Low toxicity |
| Fresco: | No (organic, fugitive) |
| Tempera: | Yes |
| Oil: | Limited (fugitive) |
| Chemical description: | Complex mixture of flavonoid glycosides (rhamnetin, quercetin derivatives) precipitated with alum on chalk or potassium carbonate substrate |
| Visualization: | Visible microscopy, UV fluorescence |
| Identification: | FTIR, Raman, HPLC |