I am guessing that I have been teaching folks to draw and paint with watercolours for at least a dozen years. If I were to replace myself with a robot that only spoke one word, it would be "DARKER!"
Getting shadows dark enough are key to making what you draw and paint look three-dimensional.
The painting below is not finished. The shadows between the pots are now dark enough. Do you see how the shadow is darker on the right side? The graduated shadow on the red pot is helping it look cylindrical.
This artist also experimented using salt with a highly granulated paint on the right side of the background. Amazing how well it works.
The bottle painter below is relatively new to working in watercolours. She uses reference photos found on Pinterest to help her learn techniques.
Two of our Wednesday night artists were beginning new paintings and the one below finished hers. Again, darkening some lines helped to balance the painting out tonally. It seems you need a little bit of every tone: light, mid and dark to make a painting sing.
And, then there is a different conversation about art and darkness. Clearly, Leonardo was not speaking to watercolourists.
“A painter should begin every canvas with a wash of black,
because all things in nature are dark except where exposed by the light.”
Leonardo da Vinci