Our January guest Tom Shepherd came with this sketch and two hours later he'd transformed it to a vibrant acrylic painting of parrots.

As you can see Tom's first concern is the light. He made sure that his original sketch had accurate overall shapes. Then he emphasised contrasts, working from muted to saturated colours; thin to thicker paint; bold to more refined shapes. When he added colours to the shadow areas he maintained the shadow tone. He continually checked shapes and tones, deciding what the painting needed rather than being a slave to the reference material.