Mediums are used to change the properties of the paint, for example the thickness, gloss, flow, drying time, transparency and durability. If an extreme thinning is required, it is advisable to use acrylic medium instead of water as the addition of large amounts of water can release the pigment from the binder into the paint; the pigment would then lie unprotected on the painting and could rub off.
Acrylic Medium, Gel Medium, Heavy Gel Medium and Extra Heavy Gel Medium can be added to the paint unlimitlessly.
The binder for both acrylic paint and acrylic mediums consists of a dispersion of acrylic resin particles in water. As long as the binder contains water, the binder is white. When all the water has evaporated after drying, the acrylic resin particles in the binder form a continuous colourless transparent film and the white will have disappeared. This explains why the acrylic paint colours become darker as they dry. When mixed with a medium the wet paint therefore also becomes a little lighter; once dry the colour is the same as pure dried paint.
Royal Talens supplies Gel medium, Heavy gel medium and Extra heavy gel medium, all in both glossy and matt varieties.
Gel medium is as thick as Rembrandt and Van Gogh acrylic colours and a little thicker than Amsterdam acrylic colours. In terms of consistency, Gel medium is thicker than the above types of paint, the gel does not flow so easily. The addition of Gel medium to a paint allows for a clearer brush stroke/structure. Heavy gel medium increases the brush stroke even further. Using Extra heavy gel medium it is possible to apply very sharp structures and extremely thick layers. Furthermore, all gels, pure or mixed with paint, due to their large adhesive capacity are ideally suited to incorporate materials such as sand, sawdust, paper, wood, stone, etc. in the paint.
