The effect
A darker perimeter fading to a brighter centre reads as depth and projection: the lip looks fuller and more sculpted, similar to a carefully blended lipstick-and-liner look. A reverse gradient (brighter at the edge) can emphasise a defined border.
Technique
The artist builds extra shading layers in the border zone and fewer toward the centre, blending the transition so there is no visible step. The border is still never a hard line — it is a band of higher density. Colour is usually a touch less sheer than aquarelle so the gradient is visible.
Who chooses it
Clients who liked wearing lip liner, who want maximum (illusory) fullness without filler, or whose border has significantly flattened. It is less forgiving as it ages than a blur — the gradient can go slightly patchy — so honest maintenance matters.
