Liquids
“The liquid portion of the paint (also referred to as the “carrier”) provides a way to get the pigment and the binder from the container onto the surface that is to be painted

• For many oil-based and alkyd paints, the liquid component is paint thinner, which is a combustible solvent made primarily of mineral spirits, a petroleum distillate of aliphatic hydrocarbons.

• For many solventborne coatings, such as epoxies and urethanes, a solvent that is “stronger” and more flammable than paint thinner is used as the main carrier, such as MEK (methyl ethyl ketone), toluene or xylene.

• For acrylic latex coatings, the liquid is primarily water (but see Additives section also, as small amounts of solvents called coalescents are used in waterborne acrylic coatings).

The pigments and the binder are what is left on the surface when the paint dries and the liquid portion evaporates. Together, they are called the solids portion of the paint:

PIGMENTS + BINDER = SOLIDS

The coating consists of the solids and the liquid:
SOLIDS + LIQUID = COATING

Thus, a higher solids content can provide a thicker dry paint film, which results in better hiding and durability. For this reason, it is recommended that paints not be thinned unless necessary (such as for application by spraying), since thinning reduces the solids content of a paint per unit of volume. For solventborne coatings, thinning with extra solvent can also increase the volatile organic content (VOC) of the applied coating. The solids content of a paint is often listed on its spec sheet. This can be expressed by weight or volume. The weight solids of a paint are usually higher than its volume solids. Volume solids are the better indicator of performance. Industrial acrylic latex paints generally range from 25 percent to about 45 percent volume solids, depending on type and quality. Alkyd and oil-based paints can exceed 50 percent volume solids, and there are some epoxy coatings that are available at nearly 100 percent solids.

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