Did you know that all paints – regardless of what their intended purpose is – are made up of both solid and liquid components that can be broken down into four categories?
The four basic categories are;
Pigment – this provides the color and hiding characteristics. Typically TiO2 or less expensive extender pigments like clay, talc, or calcium carbonate.
Binder (resin) – this holds the pigment particles together and provides the adhesion. In latex paints the binder is generally classified as either 100% acrylic or vinyl acrylic (aka PVA or poly vinyl acetate)
Liquid – this is the carrier for the pigments and binder. Water in the case of latex paint, generally mineral spirits in an oil based paint.
Additives – also known as the bells and whistles. These can range anywhere from things that enhance flow and leveling, to Microban® or other additives for mold, mildew, or algae resistance, ceramic microspheres for added durability, flash rust inhibitors, anti-spatter ingredients, etc. While additives make up a very small amount percentage wise in the total volume of a can of paint they can add significantly to the overall cost.
Since the liquid evaporates as the paint dries, it is the solids that adhere and remain on the substrate. For this reason they are extremely important in the longevity and performance of the coating. As a rule of thumb paints with a higher volume solids i.e. 40% vs. 30% will dry down to a thicker film, have better hide, and provide better protection for the substrate. The volume solids can always be found on a product data sheet. That being said, you don’t always know what is making up the solids content. Two products can be close in volume solids percentages, however Product “A” might contain a higher percentage of TiO2 and a quality resin while product “B” may be comprised of a lot of cheaper filler pigments like clay and an inexpensive resin which then equals apples and oranges.
Kevin Larson, Hirshfield’s Paint Manufacturing