Layer adhesion describes how well a colored pencil deposits color over existing layers of colored pencil.
A pencil with good layer adhesion can add color over previous applications, allowing the artist to build color, mask color, shade colors, glaze, or adjust the temperature of colors.
Poor layer adhesion may cause the pencil to slide over existing layers without depositing much additional color. Other adhesion issues include wax-ball pilling, digging and trenching, as well as dusty shedding.
Layer adhesion is influenced by the pencil's formulation, the amount color already on the paper, the opacity of the colors already on the paper, and whether the tooth of the paper can accept more layers.
Layer adhesion is different from paper adhesion. A pencil may adhere beautifully to bare paper but struggle to deposit color over previous layers, even when the paper has remaining tooth.