Sylvie asked recently: “(My instructor) says white dulls down the colour … I always use white to lighten a colour.”
I would say you are both in fact, right. Adding white is lightening (the value) and at the same time diluting the colour intensity (maybe your Instructor would say dulling). On a uniform background, that would be the only way to lighten a swath of colour – creating a tint of the colour (pure colour mixed with white) and that process comes with a reduction of chromatic intensity. In real-world painting situations, darkening (increasing the value) of the local area adjacent is a good option as that will make the colour area appear lighter and without a reduction of intensity – that’s because there is now a higher value contrast. In order to both lighten the value and retain the original colour intensity you could indeed add a little white (thereby diluting) and also add the complement adjacent .. so, bringing back the effective colour intensity. Even though the colour would be washed out somewhat, it would now appear as brighter because there is now a higher complementary colour contrast. Phew!
Break-a-Brush!
David