Acrylic mediums are added to acrylic paint to change the paint’s character or behaviour. Gloss medium is used to increase sheen and luminosity while the matte medium is used to reduce sheen and make colours look flat. Gloss medium also makes the paint more transparent.
Glazing medium, which reduces opacity and increases transparency, is suitable for glazing techniques and layering. Gel medium adds body to make the paint retain brush strokes. Modelling paste works in the same way but is thicker and can be used to create a 3D finish. Texture medium changes the surface of paint by imitating ceramic stucco, sand, glass bead and more. Airbrush medium can be used to dilute paint to a fluid consistency for watercolour-like washes.
Retarders and flow improvers are not mediums; they are additives that affect the chemical composition of the paint. A retarder is used to slow drying time while flow improver helps with absorbency and blending. Additives should be used sparingly to avoid making the binder unstable.