M. Graham Matte Medium contains environmentally friendly matting agents which creates a low sheen effect.
Using Matte Medium is recommended over water alone as excessive use of water as a diluent decreases the strength of the acrylic film. By adding Matte Medium to the water, it increases the adhesion, flexibility, and durability of the paint film.
To dilute acrylic color, make a mixture of 50% water to medium and add to color until desired consistency is achieved. It will increase the transparency of the paint by adding matte medium.
Available in store: 118ml
*description taken from M. Graham