The binders are known to be film-forming (capable of forming a film). Their role is essential. They ensure the cohesion of all the ingredients of the paint, forming a uniform film that traps all of the raw materials of the formulation. They provide pictures of properties such as adhesion on materials, chemical resistance, mechanical strength, ...).
They are polymers (or macromolecules) that can be derived from natural products (dextrins are used for gouaches) or formed by the synthesis from small molecules of gas or liquid at room temperature (monomer): In the case of vinyl polymers such as acrylic, they are in the form of dispersion in water in water based paints.
In the case of our acrylic paints for artists, the only dispersions that are used are transparent in the wet state. This helps to minimize the difference in colour between the wet paint and the dry paint film.
On the left, is a water dispersion of acrylic polymer particles of average size of 200 nm.
On the right, is a water dispersion of acrylic polymer particles of average size of 50 nm.
The same polymer dispersions as illustrated earlier, this time tinged with the same quantity of the same pigment. The dispersion which has the particle size of the finest acrylic polymer remains a very similar shade of colour when wet as is obtained on the dry paint film.