Today let’s experiment with the value ranges and intensities of different yellow watercolor pigments.
Below is a photograph of a graduated wash of all the yellow pigments in my paintbox. From left to right: Ochre yellow, New Gamboge, Naples yellow, Hansa yellow, cadmium lemon yellow, cadmium yellow medium, cadmium orange, and Holbein’s proprietary Jaune Brilliant.
To repeat this experiment for yourself, draw a rectangle with lightly marked individual squares. Fully charge your brush with pigment, using only enough water to make the paint liquid and paint the first square. Make a graduated wash by dipping your brush in water, knocking off the excess, and starting at the end of the first square, paint the next square. By stroking your brush along the side of the previous square each time you start a new row, the pigment will flow from the concentrated end to the diluted end of the color strip.
By converting this photo to grayscale and measuring with Photoshop’s eyedropper tool, we can see that none of the yellows renders more than a light mid-tone value, even painted with a brush fully charged with concentrated pigment. Value ranges from a dark 145R, 145G, 145B for New Gamboge to a pure white 255R, 255G, 255B for the Hansa yellow light.
Painting a value strip repeatedly with the same diluted concentration of pigment in water allows you to accurately measure the increasing intensity of yellow. I adapted the following exercise from an assignment in mixing shades of black on page 96 of Contemporary Botanical Illustration: Challenging Color and Texture by Rosie Martin and Meriel Thurstan .
To measure the relative strength of the yellows on your own palette: Draw a thin rectangle for each yellow in your paintbox and divide each into 10 equal squares.
Mix each paint roughly 1:10 with water and paint each strip evenly with one of the yellow washes.
Let dry thoroughly, then repeat 9 more times with the same diluted paint mixture, each time painting one less square. At the end of the experiment, each rectangle should have one square that’s been painted 10 times, 9 times, 8 times, etc.
As you can see, even with 10 coats of watercolor, none of the yellow paints provides a deep or intense value tone!
Next in this series: Mixing colors to render shadows on yellow objects.