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How to Evaluate Quality of Paint
The primary function of architectural coating is to protect metals, wood, and other materials against corrosion and decay. Where house painting is concerned, one of the prime objectives is to ensure that paint remains bonded to its substrate, and that it retains its essential properties for as long as possible. Selection of the right paint material is absolutely crucial in achieving this objective.
As house painters in the good-ole USSR in the 1970s, we were expected to make our own paint (see My Story). It seems totally nuts to me today that we were expected to do this, or sometimes even cook raw animal bones to make glue for use as a paint binder. But we did what we had to do. However, one good thing that came out of all this is that I really learned about what’s in a bucket of paint, and this subsequently led to a greater understanding of what makes one gallon of paint better than another.
So, what’s in that bucket of paint? Your four basic paint ingredients are: Pigments, Binders, Additives and Solvents.
Solvents (also called vehicles): These are quick-to-evaporate liquids (water for the latex paint and mineral spirits for the oil based paints) that keep binders and pigments in suspension and make it possible to be applied. The solvents will evaporate and leave a continuous film of pigment and binder.
Pigments: Pigments are finely ground particles that give paint its color and opacity (ability to “hide” the surface it is applied to.)
Binders (also called resins): Binders glue pigment particles together after the solvents evaporate to form a paint film, and glue the paint film to the surface being painted.
Additives: Among other things, additives control the drying time, paint leveling and mildew growth. Most of these additives evaporate as paint dries.
By varying the amounts and types of pigments, binders, solvents and additives, paint manufacturers can create a large variety of paints and, as they substitute lower quality/cost ingredients for higher ones, they can manipulate their costs and profits. For example, the term “pigment” is also used to refer to extenders, which are materials such as clay, mica, and silica. That, among their other properties, adds bulk to the paint without significantly adding to its cost.
To be able to truly evaluate paint quality, we need to have some understanding of what we expect from our paint and what causes the paint film to fall short of our expectation.
My ideal paint would stick to anything, have one coat coverage, go on smoothly, be tough yet flexible, and would last for decades while never fading. Though such ideal paint will probably never be invented, this can give us a standard to which to align a paint quality index, where the highest quality paint will be the one that approaches closest to our envisioned ideal.
Sun radiation, ultraviolet (UV) rays in particular, is the main enemy of any paint coating. It breaks down the paint pigments and destroys the bond between pigment particles, as well as weakening the bond of the paint film with the painted surface. It does this by attacking the bonding resins. Consequently, our paint film gets brittle and becomes permeable to moisture. With moisture in the substrate the paint film cracks and eventually peels.
The answer to higher paint quality is in using those pigments and binders that better resist the damaging effects of sun radiation.
So, what are those higher quality pigments and binders, and how do we know which paint has more of them?
The most often used pigment in paint is titanium dioxide (also called titanium white.) This pigment is highly reflective of UV rays and has exceptional hiding qualities. Titanium dioxide is a mineral that occurs naturally in the earth crust. Mined only in a few locations in the US, it is probably the most expensive pigment in commercial paints. Higher quality paint will contain a higher concentration of it. Lower quality paints will have a higher percentage of lower quality and cheaper price pigments and fillers such as clay, silica and talc.
Higher quality paint will also have better binder, so it sticks better and better resists wear. The best latex binders are made of acrylic, and best acrylic binders are made from small particles. The smaller the particle, the deeper it can penetrate the pores of the surface you are painting and “grab a hold of it”.
You can do an experiment: Take a flat wooden board and score the top of it up with a knife. The groves will imitate the painting surface pores. Now place some coarse sand or small pebbles on top of your board, then turn the board over. Your pebbles will just roll off the board. Now repeat your experiment but use talcum powder on top of the board instead. This should demonstrate to you that smaller particles grab on better. Still not convinced? Repeat the experiment but now sprinkle some water on top as a final step. Water, the vehicle in your latex paint and probably the one of the most penetrating substances on the planet, will drive your paint ingredient particles as deep as a circumference of a particle will allow.
Binders are the most expensive ingredient in paint. At a paint store, you’ll usually find paint labeled either “acrylic” or “vinyl acrylic.” Vinyl binder is much cheaper than acrylic but the more acrylic resin you have in the paint, the better it will hold up and adhere to a surface. Go with the 100% acrylic!
Note: Because it is binder that makes glossy paint glossy, a glossy paint will contain more binder than flat paint. Still, a higher quality gloss paint will have more and better quality binders than a lower quality glossy paint.
Lower quality paint will also tend to have more solvents. In latex paint, solvent is primarily water. The cheapest ingredient of all, water doesn’t have to be transported or stored. Just open the facet and pour. Such paint can by volume contain over 70% of it. More water means less solids, and a lower percentage of solids will result in a thinner dry paint film, with lesser hiding and durability.
If higher cost ingredients are required to produce higher quality paint, one can understandably come to a conclusion that by buying the most expensive paint, one is getting the best quality. This is not necessarily the case. I often see lower quality but well marketed paint being sold at a higher price than paint with better quality ingredients.
The other day I got a call from someone, calling from somewhere across the country, asking me for who’s paint I would recommend. I am not here to endorse any one particular paint manufacturer. The fact is that, on our paint projects, I will often use materials of multiple manufactures. For example, I may use wall paint of one manufacturer, rust inhibitor of another, and yet a completely different one for the floor paint. I will use whatever product I find to work best for a given surface or circumstance. As with anything else, there is no substitute for understanding of what makes the difference.
OK, how do we find out what is really in that gallon of paint? Unfortunately, the paint ingredient information is not readily available on a paint can label. So, if you really want to know, you will have to go searching for it in the paint manufacturer’s Technical Data Sheet (TDS) and Material Safety Data Sheet (MSDS). I will put a few links to this information below, but unfortunately even there this information is pretty well coded. Let’s decode some of that lingo:
Solids: All the resins and pigments left behind after the solvents evaporate (paint dries). Solids are usually shown as a parentage of volume and are expressed on the TDS as Percentage of Non-Volatiles or Solids by Volume. Example: 53.4% by vol. (Remember, a low percentage of solids means a thinner dry paint film with poor hiding and durability.)
Dry-film thickness (DTS): Each paint is formulated to attain a certain thickness, measured in mils, when brushed or rolled out. One mil is one-thousandth of an inch, about one-quarter the thickness of human hair.
Coverage: This is usually expressed as square feet per gallon and is handy in calculating how much paint you need to buy. Example 350-400 sf/gal.
VOCs: The abbreviation stands for volatile organic compounds – solvents that are emitted from paint and adversely affect our lungs and air quality. Federal regulations limit the amount of VOCs in paint.
With the price of paint at such a relatively small percentage of total job cost, I see absolutely no reason why someone would want to use inferior quality materials on a paint job, but it is done all the time. Also, it seems that some paint manufacturer’s formula of business success lies in spending their energy on marketing and public relations in lieu of using better quality paint ingredients. As a businessman I can understand – marketing helps to sell paint. It is a free country and it is their business and they are free to do whatever they feel they must do. Yes, I have no problem with this, but only for as long as it doesn’t interfere with what I feel I must do: “Great looking, long-lasting paint job”. So, as an educated consumer, I will simply not buy their product.
Here are a few links, for more commonly locally used paint manufacturers, where you can find the manufacturer’s technical data (Given in an alphabetical order): Behr, Benjamin Moore, Kelly Moore, Sherwin Williams.
Note: When comparing products, be sure to compare “apples to apples”. I.e. base to base (deep paint base to deep paint base, white base to white paint base) and sheen to sheen (flat paint to flat paint, semi-gloss to semi-gloss, etc.)
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p.s. With the above said, it’s important to add that even the most expensive and best quality paint will be totally useless in producing a long-lasting paint film, if it is applied over an unstable or infirm surface. (See Importance of Paint Surface Preparation and Steps for Paint Surface Preparation.)