Coloured Paper and Gouache

In the following studies I have used watercolours over coloured paper that has been covered with a light wash of white gouache. I read about this technique in an article about the work of artist Jane Corsellis (Watercolor August 2010).  The gouache has a chalky quality that depending on how vigorously the brush is used can be mixed with the watercolour giving it a milky opaque quality, in the initial attempts I found this technique worked well when painting the sky.