“Green is the prime color of the world, and that from which its loveliness arises.”
Pedro Calderon de la Barca (from the paintedprism.blogspot.com)
The perfect green for the leaves of the trees and the grass of the fields has a name that misleads. Sap green was not made from the sap of trees or leaves or grass. Berry green would have been a more appropriate name. More precisely, sap green was made from buckthorn berries and stored in animal bladders. Why animal bladders? Beats me! For some reason, bladders seemed better than jars to these early makers of sap green, perhaps because at the time this green was known as verde de vescica. (Since my knowledge of animal bladders and what they have to do with paint, is limited, we will move on.) It is an old paint color and early painters of illuminated manuscripts considered it part of the four primary colors needed in their work. Red, yellow, blue and green were the primary colors of these artists. Sap green was the primary green. Unfortunately, the early sap greens were not lightfast as they are now.
Channeling-winslow-homer.com describes Winslow Homer’s use of Hooker’s green and sap green in his wonderful landscapes. Homer’s The Blue Boat is featured on the website and is a great example of the lovely green grass that can be made with mixtures of sap green. Susanart.com claims to have found the perfect “luscious” mix of sap green using Schmincke sap green and Schmincke translucent orange for richgrass and moss. Gamblin states sap green warms nicely when mixed with Hansa Yellow and cools nicely with any of the blues.
Daniel Smith’s website describes techniques for using sap green’s staining ability in paintings. Removing sap green from a painting, whether in oil or watercolor, leaves a green stain behind that creates many different wonderful effects. This staining ability is the main reason sap green is favored in the layers needed for glazes in botanical painting. Daniel Smith’s description goes on to point out which color mixes will make the best deep shadowy forest greens or the more olive tones of mossy greens.
Sap green is a must have in all paint boxes, especially for landscape painters. Whether or not you make your own pigment, sap green is essential for wonderful lovely green mixes. The adventurous may try gathering and boiling down the berries to see what happens. Since buckthorn is wild and grows profusely, it should be easy to find. Animal bladders may not be so easy. Good luck finding them.
Winsor-Newton demonstrates sap green washes in the following You Tube video.