Paint is made up of solvents, pigments and resins. A solvent is the liquid carrier that suspends the pigments and resins. It allows the paint to spread evenly and then evaporates as it dries. Pigments are particles which give paint its color, and resins bind those pigments together to create the "film" of the final product.
So, just what's the difference between that $12 gallon and a seemingly identical $30 gallon next to it on the shelf? As you may have guessed, the bargain paint is diluted with more solvents (liquids) and contains larger particles of pigment. Better quality paint will be more concentrated with finer pigments and higher grade resins, so the final product will have more even color and a more durable finish. And that means one coat instead of several to cover your surface.
It's tempting to want to save money up front, but remember, better coverage means less paint to buy; you could easily wind up spending just as much for two coats of a less expensive formula. Even reputable brands have a range of paint qualities within their product lines, so make sure to do your homework and buy the best you can afford.
(Image: Carolyn Purnell)