I’m slow in the summer, but I’ve finally completed my underpainting! At this stage, I need to decide how I want to handle my cast shadows. I always like to glaze them, as opposed to painting them in body color, because they look more transparent. My usual method would be to ignore the cast shadows in both the underpainting and the initial overpainting. For example, I would paint the wall one uniform color. When the overpainting is dry, I would glaze the shadow over it. The advantage to this method is that it beautifully mimics the look of a transparent shadow cast onto a colored surface, since the actual color of the wall would show through the glaze. There are two problems with this method. First, it can be difficult to achieve a soft edge on the glazed shadow. Second, I’d be left with no guide as to the location and shape of the shadows, since I would have obliterated my drawing with the under and overpainting!
An alternative method to handle cast shadows is to paint them in the underpainting. Then, when applying my first layer of the overpainting, I would paint the shadows with body color in my best guess as to their color, but keeping the value much lighter than I want ultimately. Working wet-in-wet, I could blend the shadow edges softly. When this layer is dry, I could then glaze a darker tone on top to achieve the transparent look that I like my shadows to have. Using a cotton pad, I can feather out the edge of the glazed shadow to just before the painted shadow ends. This is easier to do than to try to get a perfectly soft blended edge with the glaze alone. Any irregularities are masked by the smooth painted edge underneath.
Since my cast shadows are difficult to draw correctly, I think I’ll use the second method, so as not to loose my drawing.