My last post had to do with how to produce a painting that uses glazed colors rather than palette-mixed colors. This post goes deeper and discusses how to use glazes to produce the color green. In order to understand how the color green is created using glazed layers of paint, it is important to know how pigments reflect color from a white background. You are probably already familiar with the color wheel of primary colors: red, blue, and yellow; and secondary colors: orange, violet, and green. To make green, blue and yellow layers of glazed color need to be applied. For each pigment, there is a cool version and a warm version of the color. For blue, a warm version is Ultramarine Blue, and cool versions are Pthalo Blue and Cerulean Blue. For yellow, Hansa Yellow and Lemon Yellow are cool, and Cadmium Yellow Light is warm.
The reasons why a color is warm or cool lies in how it reflects light. Cool, green-blues, such as Cerulean and Pthalo Blue reflect blue followed by green and then a lesser amount of violet. Warm, violet-blues, such as Ultramarine reflect blue followed by violet and then a lesser amount of green. Cool, green-yellows, such as Hansa Yellow and Lemon Yellow reflect yellow followed by green and then a lesser amount of orange. Warm, orange-yellows, such as Cadmium Yellow Light reflect yellow followed by orange and then a lesser amount of green. Yellow Ochre, a subdued, dull orange-yellow, reflects small amounts of yellow and smaller amounts of orange and green.
Glazing is the optical mixing of the glazed layers with the underpainting. However, when paints are mixed on the palette and then applied to the underpainting, the mixing is physical, not optical. The results of optical mixing are quite different than those of physical mixing.The combination of the reflection and refraction of light in optical mixing provides the luminosity associated with glazing.
To mix a bright green through glazing, intermingle a green-blue layer with a green-yellow layer. Thus, intermingling Hansa Yellow layers with Phthalo Blue layers produce a bright green. The end result will also vary depending on how many and how often layers of yellow and blue are glazed over each other. Experiment by laying down yellow first or blue first. Alternate layers of the blue and yellow, or lay down the blue followed by several layers of yellow to get more of a yellow bright green. Prussian blue, which is also a green-blue may be used instead of Phthalo. Experiment to discover which combination you like more for the specific application. Using Cerulean Blue instead of Phthalo Blue will also give a bright green, but it will be less bright than when using Phthalo Blue because Cerulean reflects less green than Phthalo.
A mid-intensity green can be created by intermingling Hansa Yellow, a green-yellow, with the violet-blue, Ultramarine Blue. Again, experiment with how many and how often you apply the layers of yellow and blue. A combination of Cadmium Yellow Light, an orange-yellow, and Phthalo Blue, a green-blue, will give another type of mid-intensity green. Since the Cadmium Yellow Light is an opaque pigment, it should be laid down first at part of the underpainting. To get a dull green, mix an orange-yellow with a violet-blue, where green is the least reflected color. A Cadmium Yellow Light laid down first and then glazed over with an Ultramarine Blue is a good combination for a dull green. Yellow Ochre is considered to be a muted orange-yellow, as it reflects only a tiny amount of green. Intermingled with Ultramarine blue, it gives the darkest, dullest green, a brown-green.
I hope this gives you a good basis for mixing glazed greens. As long as you can identify the secondary reflecting color of any particular blue pigment: green or violet, and the secondary reflecting color of any particular yellow: green or orange, then you will be able to understand the type of green that will come out of intermingling these colors in glazed layers. In future posts I will discuss the optical mixing of violets and oranges. Most of the information in this post was drawn from the book “Glazing” by Michael Wilcox, a book that I recommend for anyone wanting to learn more about glazing.