This is a small demo I did last week for my advanced oils students. The aim was to capture the light passing through the backlit green bottle using minimal strokes and placement of color next to color. Efficient brushwork and color placement in an adjacent rather than layering fashion is key to successful alla prima painting. Over blending and layering creates mud when working wet into wet, color needs to stay pure to be effective. The placement of dark values at the begining is also important in acheiving a look of transparency and luminoscity. You need dark darks in order for the brightest brights to look bright, otherwise the brights just compete with one another for attention and lack depth.