In the previous post, we looked into the very first decision to make about paint – the right type for a painting job at hand. Today, we continue and will discuss paint’s coverage – a topic of the great importance to painting contractors.
When talking about paint coverage, we will be talking about two things: the paint’s ability to cover the old paint/imperfections and the amount needed for a job.
The ability of paint to cover depends on paint’s content, more specifically, on binder, pigment and vehicle (and some additives).
Binder is what ensures adhesion and creates a resulting paint film. In other words, binder holds the pigment particles together into a solid film after the solvent has evaporated. Acrylic (in latex paints), epoxy, oil, polyurethane, etc. are examples of binders.
Pigments give paint color. They are classified as prime and extender pigments. Prime pigments are called that way because they are the primary color providers. However, they are expensive. That is why they are supplemented by the extender pigments to lower the cost of paint. The proportion of prime and extender pigments is one of the main factors determining the price and quality of paint, including coverage. The more of the prime pigment is in the paint, the better the paint’s masking qualities will be. The evenness of pigments’ distribution and their reflective qualities will also influence the hiding ability.
Vehicle determines the liquidity of the paint and is another determining factor of paint’s coverage. Pigments and binder together comprise the solid part of paint formula. The proportion of vehicle to the solids has the opposite outcomes for two aspects of coverage. Thinner paint (bigger vehicle content) will cover more of a wall surface, but at the same time will be worse at hiding the old paint or imperfections. And vice versa, thicker paint will be covering the surface better, but will cover less of it. This is a tradeoff contractors providing the painting services should be aware of to give you the correct estimate and quality assurance. The thing to remember is that many times buying a little more paint will still be cheaper that having to apply a second coat.
Paints with 30% to 45% of solid components are considered high quality with better hiding abilities.
Paint also contains various additives. Some of them influence paint’s coverage, for example, thickeners, surfactants, and dispensers (providing the enhanced light reflection for improved hiding qualities).
Note: The average surface coverage of a latex paint is 350 sq. ft. per gallon. This number will be different for various formulas, as we explained earlier. Plus, the condition and type of surface (rough/porous/very old paint will absorb more paint) as well as the desired hiding level will mean more or less paint will be required. The degree of color difference between the old and the new paint will also influence the coverage rate.
This all for today. Tune in for brand and finish discussion in the next post.