Unifying surface sheen
Different pigments in acrylic paint naturally dry at different sheens — some glossy, some matte. Mixing a consistent amount of gloss or matte medium into all colours unifies the surface.
Gloss glazing: Mix a small amount of colour into gloss medium for a thin, transparent glaze. The gloss intensifies the colour beneath, creating depth without opacity.
Matte washes: Combine matte medium with flow improver and a small amount of colour for flat, even washes. The matte prevents any reflective interference with the colour reading.
Semi-gloss custom mix: Combine gloss and matte medium in equal parts for a satin finish — useful when neither extreme is appropriate.
Gloss mediums make colours appear richer and more saturated — this is the same optical effect as wetting a dry stone. Matte mediums scatter light diffusely, which can make colours read slightly lighter and less intense. Neither is better — choose based on what the work requires.