Underpainting a portrait painting after Rubens

This shows the second pass on the underpainting. Underpainting is when you paint using only a very few colours and lay a foundation for the colour glazes which go on top. Here I used Raw Umber and Titanium White. It is possible to use other colours to do this and this video is not definitive, but it is highly likely that Peter Paul Rubens used this in his paintings. I have also done underpainting using a Black and White (again for me any black is OK, and its also nice to mix an optical black using Burnt Umber and Ultramarine Blue or something like that).