Sap Green

What color is sap green?

The story of sap green

Sap green started life as berry juice in a sheep's bladder, and every tube that carries the name today is a stand-in.

Buckthorn was the source: a thorny shrub of the genus Rhamnus with small fruit that turns black or red as it ripens. Some recipes used ripe berries and some unripe ones. Either way the juice was pressed out, boiled down and fixed with alum, the old trick for turning a dye into paint. It was never dried and ground like other pigments. It stayed a dense syrup, and the illuminators of the Middle Ages bought it that way, in dried sheep's bladders, for the greens in their manuscripts. The trade names, Avignon berries and Persian berries, say where the supply came from.

The trouble was that it faded. Sap green is a plant dye, and plant dyes do not like daylight. Shut inside a book it lasted for centuries, which is why we can still see it in manuscripts; out in the open it went the way of grass stains on a pair of jeans. Painters used it anyway, in France and England right through the 1700s, because nothing else gave that soft yellow-green. As early as 1652 an English drawing manual listed a grass green made from a buckthorn yellow called pink mixed with blue, so the appetite for a leafy green was there long before the chemistry was.

What you buy today has no berries in it. At some point the name came loose from the recipe and became the description of a hue. Open a modern tube of sap green and you will find a phthalo green, PG7 or PG36, warmed up with a yellow: nickel azo yellow in one brand, quinacridone gold in another, a brown earth in a third. That is why sap green from two makers never quite matches. One leans olive, one leans lime, one is nearly a Hooker's green. The label promises leaf; the recipe is whatever the chemist decided leaf looked like.

Beginners reach for sap green first, and I think they are right to. It is the one tube green that looks like something that grows. Phthalo green looks like a sports drink and viridian looks like sea water, but sap green straight from the pan is already a plausible leaf, and it turns into a hundred other plausible leaves with a touch of anything else. Bob Ross kept it on his palette for The Joy of Painting, which tells you how far a berry juice can travel.

Here is my take. Sap green is a convenience color pretending to be a pigment, and I do not mind at all. The old one faded and the new one does not, so the trade is a good one. What I mind is people treating it as the answer to every green. Add a little of something red and it becomes the green of August; add a little blue and it becomes the green of shade. On its own, wall to wall, it is the green of a paint-by-numbers kit.

Pigment facts

These describe the pigment in general. Every brand's tube behaves a little differently, so test yours on scrap paper.

How to mix sap green

You can mix a very good sap green yourself, because that is what the tube is: a cool green pushed toward yellow. Phthalo green with a warm yellow, about one to three, lands on it. The pairing that matters once you have it is sap green with burnt sienna. Equal parts give a warm olive for late summer, more sienna gives tree bark and dead grass, and a touch of sienna in a lot of sap green gives the ordinary green of a hedge, which is the hardest green to mix from scratch.

Do not darken it with black. Black turns sap green into a swamp. Use a blue or a red-brown instead, and keep the wash wet while you do it.

Using sap green in watercolor

Use it for the middle distance: the yellow-green of a sunlit field, the general mass of a summer tree, the grass under a picnic. Sap green is the green of a landscape at noon, before you start deciding what is in shadow.

My favorite way to use it is as a first wash. Lay a thin, wet layer of sap green over everything that will eventually be foliage, let it dry completely, then build the darks on top with sap green plus ultramarine or plus burnt sienna. Because it is transparent and does not granulate, the first layer glows through the second and the whole tree hangs together.

It pairs with the earths. Burnt sienna and yellow ochre next to sap green make it look natural; a cool red like Poppy Bloom makes it look expensive. Keep the true blues and violets for the shadows.

One thing I learned the hard way: a painting made entirely of sap green looks like a putting green. I did a whole hillside in it once, straight from the pan, and it came out flat and a little sickly. Every patch of green outdoors has some red or some blue in it. Give each one a different touch and the picture starts to breathe.

Sap green vs Hooker's green (and olive green)

Hooker's green is the one sap green gets confused with, and the two are cousins. Both began as plant colors: sap green from buckthorn berries, Hooker's green from Prussian blue and gamboge, mixed by a botanical illustrator for painting leaves. Both are mixtures today. The difference is temperature: Hooker's green is darker and cooler, a green for the underside of a leaf; sap green is lighter and yellower, a green for the top of it.

Olive green is the other neighbor, and it is what sap green becomes when you dull it. Add a little orange or red-brown, thin it a touch, and you have olive: lower in saturation, browner, quieter. Painters who own a good sap green rarely need a tube of olive.

If sap green is the lawn, Hooker's green is the hedge behind it, and olive green is the same lawn in September when nobody has watered it.

More color stories

Mel, founder of Tobio'sI make portable watercolor kits and I named the company after my cat. I write these pages for the beginner I used to be, one pigment at a time.