At this point I lay in the composition as a light sketch on the panel (due to glare, it's not particularly easy to see in the above image).
This sketch is purely functional - it makes no effort to actually be an artistic drawing; I don't attempt to vary the line, define volume, or give depth. I'm simply placing the outlines of the objects and indicating a few salient details. Above all, I want to keep the sketch light so there's no chance it will ever show through subsequent layers of paint.
In some of the more complicate passages, like the design on the bowl above, I'll lay in some hatching, but that is simply so I don't get confused when I start applying paint.
Now that the sketch is complete, I apply a thin layer of retouch varnish (damar) to isolate the drawing so I won't get smudged or bleed into the paint.
With the next post I'll start putting paint down.