A unique green, highly sought after by landscape painters since the 17th century for its clarity and versatility in mixing, the original Sap Green was made from the juice of ripened buckthorn berries precipitated with Alum.  The resulting colour was clear and bright and not at all lightfast.  Contemporary Sap Greens vary dramatically from manufacturer to manufacturer, and many that claim permanence are dull and opaque, not at all in keeping with the clarity and depth offered by a true Sap Green.
In 1994, Winsor & Newton introduced a Permanent Sap Green, but the cost was prohibitive (it was a series 4 colour).  In 2003, however, Winsor & Newton introduced a traditional Sap Green – with the brilliance, depth, and clarity coveted by landscape artists over the last 4 centuries – reformulated to offer permanence suitable for artists’ use. 

Isoindolinone, PY110; Copper Phthalocyanine, PG36
A – Permanent; ASTM I
Series 1
Transparent
Staining