Here goes  --  Painting 101.  What we are looking at here is the same painting we saw in the first post only we now see it in an earlier state.  This is what is know in the craft as an under painting.  This technique was used by such old masters as Da Vinci, Rafael and Titian. 

 
    First, the artist draws the picture on the canvas or panel.  This drawing (known as a cartoon) is most often very finely detailed and is faithful to the final image.  Once the drawing is complete, the entire painting is done in umber, a brownish earth color.  Using umber, white and black, the entire image is painted with all the correct values - shading, so that the image looks complete and believable.  Most of us are familiar with old-fashioned sepia-toned photographs.  An under painting looks similar.
    Once the under painting is complete, the artist then applies the colors to complete the painting.  I suspect that this method was partly to conserve colors which were very expensive, difficult to acquire and time consuming to make.
    As we see the picture here, the under painting is partially complete and portions of the drawing and gesso ground can be seen.  The magic of digital photography allows us to capture and share these intermediate steps.
    Stay tuned for more images of this picture as it progresses.  Potlick