“For shadow, use Van Dyke brown with brown ochre; this can be warmed with burnt sienna, which will also raise the value a trifle. Mix a purple [shadow] from ultramarine blue, rose lake, and a trifle white.”
The above text written by Frank Atkinson in his “Scene Painting and Bulletin Art” (1916, page 165). It provides a recipe for two shadow glazes – both a warm shadow and a cool shadow. The mixture of browns and sienna was intended to be a warm glaze for many cast shadows, but not all. Often a cool cast shadow was desired in the composition. A cool purple glaze was created from ultramarine, rose lake, and a little white. Note that purple dry pigment is not used in the purple shadow glaze!
On the following page, Atkinson warns against the use purple on stage, writing:
“Caution: – All purple, regardless of value, are prone to appear too red under artificial light, and to counteract this tendency, the quality of all purples should be rather too cool when viewed in daylight.”
I found this fascinating for two reasons. The first being that there is the acknowledgement that a paint color will shift under light and become something that the artist never intended for the composition – destroying the painted illusion. Secondly, he directs the painters to mix a cooler version of what they see under natural light in the studio. It is important to remember that the early twentieth scenic studios primarily used huge windows and skylights to light the space. So the majority of drop painting was occurring in natural light conditions and not artificial light conditions.
Below are some painted details from my scenery collection (Peoria Scottish Rite, ca 1902 and enlarged for the Scottish Rite Cathedral in 1920s). They provide examples for both warm and cool shadows:
