I've been playing around with using a wash for an underpainting like oil painters do on their white canvases. I think it gives the painting extra warmth. There are no absolute whites except for a dash of chinese white on the upper right of the bowl. Needed to have it overlap onto the glass.
"Bubble Glass and Lemon", 4x3 inches watercolor on board
"Bubble Glass and Lemon", 4x3 inches watercolor on board