Binders
“Binds” the pigment and provides adhesion, integrity and toughness to the dry paint film

The binder, sometimes referred to as the resin or polymer, is a
very important ingredient that affects almost all properties of the coating, especially the following:

• adhesion and related properties like resistance to blistering,
   cracking, and peeling
• other key resistance properties like resistance to corrosion,
   abrasion, chalking and fading
• application properties like flow, leveling and film build, and
   gloss development

With no pigment present, most binders would dry to form a clear, glossy film; some binders are used without pigments to make clear finishes and varnishes.
Pigment reduces the shininess, or gloss, of the binder. By incrementally increasing pigment levels, and by using larger particle pigments, gloss levels from high gloss to flat are achieved.

Paint gloss is measured by using instrument readings of reflectivity taken at three different angles from vertical. The gloss reading at 20° serves to describe the “depth of gloss” of gloss and semigloss paints. The reading at 60° is the measurement of gloss referred to most often, and is used with all but dead-flat paints. The 85° reading describes the “sheen” of flat, eggshell and satin paints.

Paints described as flat, eggshell, satin, semigloss and gloss will generally have sheen and gloss values falling into the ranges in the table below (a standard of polished glass = 100). This is not to say that a given product will vary within the range; rather, each value for the product will be designed to be in the range described. For example, a particular semigloss paint might have a 20° gloss reading of 15, and a 60° gloss reading of 55.

The paint chemist uses a figure called the PVC (pigment volume concentration) to indicate the relative proportion of pigment to binder for the paint formulation. The PVC is a comparison of the relative volumes (not weights) of total pigment and binder, and is calculated as follows:

Typical PVC levels associated with different levels of paint gloss are noted below:

Thus, a broad range of pigmentation levels is utilized in designing paints of various sheens or gloss, and can have a large impact on the quality of the coating. For example, high quality flat paints, for both interior and exterior use, generally have PVC levels at the lower end of the range given in the above table. Because these flat paints have more binder available per unit of pigment, they will generally have better durability than higher PVC flats, all else being equal, as measured by properties such as scrub resistance and dirt resistance for interior use, and color retention, chalk resistance, mildew resistance and general durability for exterior applications.
The gloss requirement for paints shinier than flats restricts the range of PVC that can be utilized, compared to the range available with flat finishes. Some product specifications and/or MSDS will indicate the PVC of the product.

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