Last week we covered pigments. This week, on to binders, solvents, extenders and additives.
Binders are the fluid in which the pigment is suspended and are where the greatest advances in modern paint have been made.
When paint is in its liquid form, the binder acts as the carrier for the pigment. When the paint is on the wall and is dry, the binder acts as the glue that holds the color in place. To give you an idea of the relationship between binders and pigments; in matte paint the pigment is 70% and the binder is 30%. While in glossy paint, 20% is the pigment and 80% is the binder.
As with pigments, there are natural and synthetic binders. Natural binders include plant oils and resins, natural latex, casein, milk, eggs, cellulose and animal glues. Synthetic binders are alkyd resins based on synthetically modified veggie oils, polyvinyl acetate and acrylic (a by-product of oil-refining).
These are what are also known as thinners. Combine solvents with pigments and binders and you get a paint product in a usable consistency. In other words, solvents make the paint a liquid. As with pigments and binders, these also come in natural and synthetic.
Natural solvents are water (which, is typically used in water-based paints), turpentine, plant alcohol and citrus thinners. Synthetic solvents include denatured alcohol, isoaliphate hydrocarbons, and turpentine substitutes.
Solvents are also what have been charmingly referred to as VOCs or volatile organic compounds. This is due to their “volatile” nature. They will evaporate easily at normal room temperatures and all solvents contain carbon in their make-up.
That being said, today’s solvents can be safer than solvents like turpentine because they have less powerful fumes and a higher flash point.
Extenders and Additives
Extenders are exactly what they sound like they might be – they extend the paint. Or, to put it another way, they make it go further and help reduce the price. These actually have not changed too much over time. They include chalk, barites, china clay and a few others.
Additives get the paint to do different things such as having a thicker consistency. The thickener surfartant reduces the surface tension of a liquid and allows it to either foam or penetrate solids. Another additive is a biocide. This is a preservative in the paint and keeps bacteria from growing in the paint. While fungicides discourage mold growth after the paint has been applied to a surface.
Additional additives like plasticizers keep paint from becoming brittle. There are also coalescing co-solvents (say that five times quickly!) which, aid film formation qualities. Finally, another additive would be a drier. Not too much of a leap of the imagination there to determine what that additive does.
Next week we are on to a few different types of paints available today. I hope y’all have a great weekend!