How Do Solvent-Based Acrylic Paints Cure?

Composition

• Solvent-based acrylic paints owe their color to the pigment molecules they contain. The type of pigment molecule depends on the color of the paint. Acrylic polymers act as a binder or film-former to hold these pigment molecules together so they don't simply rub off once applied. Water-based paints also contain a surfactant or emulsifying agent to help the pigment and acrylic molecules dissolve in the water; solvent-based paints, by contrast, carry both binder and pigment mixed into an organic solvent. Depending on the type or brand, the paint may also contain various additives as well.

Drying

• The organic solvent in the paint is relatively volatile at room temperature. Once you open the can and apply the paint, the solvent begins to evaporate. The acrylic polymers in the paint generally form small spheres that coalesce as the solvent evaporates, slowly turning into a tough, tacky film. This film keeps the pigment -- the part of the paint that makes it colorful -- bound in place.

Curing

• Curing for solvent-based acrylic paints is essentially a physical process driven by evaporation of the solvent -- no chemical reactions are involved. This is different from more traditional oil-based paints, which cure through a chemical reaction with the oxygen in the air, and polyester wood finishes, which cure through a reaction between the ingredients in the finish itself. For acrylic paints, the curing process can truly be called "drying," because evaporation is all that is involved.

Considerations

• Once they have cured, acrylic paints are no longer water-soluble. They remain soluble in various organic solvents, however, and solvent-based paints can dissolve in mineral spirits, xylene and other similar reagents. They can also soften at high temperatures. The curing process for acrylic paints is much more rapid than the chemical process that takes place in an oil-based paint, which is one of the reasons acrylic paints have become so successful.