Why is Paint “Solids Content” Important?

You may not have thought about this much when you buy a gallon of paint, but you may be buying mostly water in that can you’re lugging home from the paint store. If you aren’t checking the solids content of your paint then chances are good that you are buying your paint based on marketing or a cool label

Every paint is made of of three main ingredients: Solvent (water or alkyd), pigment, and binder. As a paint dries, the solvent dissipates and what you’re left with is the pigment and binder, which are together referred to as the solids. The binder holds the pigment together and the two, together, create your paint film.

The more solids a paint has, the better it hides and protects, so solids are a big part of the paint formula and a higher solids content is definitely worth paying for. I wrote a few months back about a premium paint I tested to see if I could get 1-coat coverage with a dramatic color change if you’d like to check it out here.

When talking about solids content everything else is just water or paint thinner essentially. As far as solids content goes, it’s like the breakfast cereal in the box. Yes, you pay for the box and inner bag, but the only thing that really matters is how much of that delicious cereal you’re getting.

For example, if paint is applied in a wet film at a 100 μm (micrometers) thickness, and the solids content of the paint is 50%, then the dry film thickness will be 50 μm as 50% of the wet paint has evaporated in the form of the solvent.

Why Solids Content Matters

Most paints have a Dried Film Thickness (DFT) that the manufacturer recommends. That is usually accomplished by applying two brushed or rolled coats of paint, but it can be achieve any number of ways. You could apply three thin coats of paint or spray one thicker coat of paint. It really depends on the paint and application, but meeting that DFT is important or your paint won’t perform like the manufacturer claims.

There are a lot of variables, but with all things being equal a thicker DFT usually means a longer lasting paint job. For example, Paint A may have a DFT of 2.8 mils while Paint B has a DFT of 2.0 mils. Let’s say both paints are exactly the same thickness and viscosity when wet, that will mean Paint A has a higher solids content.

You apply one coat of Paint A and let it dry in one area and apply an identical coat of Paint B in another area. When everything is dry you’ll have a thicker coat of paint remaining where Paint A was applied. That means more protection for whatever you painted. Sure you could just apply additional coats of Paint B, but that means extra work and extra paint which in the end means you’re not saving any money.

Higher solid content means a few things that you should definitely be aware of.

• Thicker paint film
• Better coverage
• Potentially fewer coats
• Longer paint life
• Higher paint cost

A typical solids content for most paints is in the 30-45% range, but some high end paints and primers have a solids content above 50% which you will pay handily for.

A higher solids content is not everything, since there are some pigments and binders that cover better than others, but all things being equal, a higher solids content will mean a better paint job with a longer life. Solids are the expensive part of the paint so you will pay considerably more for a comparable paint with a higher solids content, but that extra cost is almost always paid back in spades with better coverage and longer paint life.

You can always find the solids content on the Product Data Sheet for any paint. Sometimes it’s located on the back of the can, but not always so do your do diligence before purchasing. Looking at the solids content is not the only thing to look at, but it can be a helpful ingredient to check when comparing paints to see what you are really getting in that can of paint.