We are trying to determine the best criteria for selecting an exterior paint.

Question

We are trying to determine the best criteria for selecting an exterior paint.

Asked by Daniel

Thinking of using an acrylic latex paint. Exterior color is a dark color. Performance is an issue as well as cost but getting a grasp about the criteria is what we're after.

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Answers

Joel Hirshberg's picture

Good question Daniel.

Given all the different brands of paint, it's no wonder that choosing quality paint ischallenging, even for professionals.

  • Not only does each manufacturer create differentlines of paint within each brand,
  • but each application is so different it demandsspecialized knowledge that can only be discovered through good research and reputablepaint companies.

Where do you start?

Asking the right questions

Here are some basic rules of thumb for choosing the right paint. Below them is sometechnical paint jargon that will help you ask the right questions.

1) Price and quality. Manufacturers want to make it easy for you to compare so theybreak quality down into price groups, usually in the form of different lines. Higher pricedpaint usually means better quality because the ingredients cost more.

There are manytypes of paint (latex, acrylic, alkyd, oil-based etc), and each has its intended purposeto satisfy different types of customers, e.g. professional painters, commercial painters,specialty finish painters and DIY painters.

High quality paints are:

  • easier to apply
  • flow better during application
  • hide imperfections better
  • resist fading, pealing and flaking better
  • resist mildew and
  • provide a longer service life

The bottom line is that premium paints save you time and money . . . .however . . . .

2) Health and safety. Just because paint performs well and is expensive does not makeit safe. Most people believe low or no VOCs equals healthy paint.

  • However, no or low VOCdoes NOT equate with healthy.
  • The best performing paint may contain plenty of toxicingredients that are not regulated or are proprietary and not disclosed.

Recently, a leading paint manufacturer blew the whistle on one of its chief competitorsfor claiming to have zero VOC paint. While the paint was zero VOC, the pigments werenot, and the combination increased the VOC level far above what was claimed. Theywere busted by the Better Business Burea.

Do your homework before you visit the paint store. Go online and download the MaterialSafety Data Sheets (MSDS) for ingredients and hazardous chemicals. Check sections 2 ,3 and 11 as it will spell out most of the important information you need to know.

3) Durability. Higher quality paints have more solids content and less liquids (diluentsor solvents-see below), which results in a thicker longer lasting film.

  • Paint that is filledwith inexpensive fillers doesn't hold up to scrub tests, and the best paints (glossier thebetter) contain 100% resin.
  • Check section #2 of MSDS for composition of solids contentby volume and weight.

4) Protection. One of the main purposes of paint is to seal the sheetrock, wood, or
masonry beneath it.

A thicker coating with more solids content locks out moisture andkeeps everything dry underneath it.

  • Some high-end paints are so thick and tough theyrequire neither priming nor a second coat. This saves time and money.
  • Less expensivepaints are thinner, require more coats and wear off easier.
  • The pros usually test paintquality in between their thumb and forefinger to get a feel for how thick and smooth it is.

5) Beauty. Most paint companies offer great color options but what is critical is howlong they continue looking good.

If the pigment is not of high quality, that nice paint jobover time will lose its luster.

  • Inexpensive paints fade, wash off and are not consistent.
  • It'shard to tell this from reading the side of the can, and you can't judge it except over time.
  • That's why you have to check references and inspect homes painted years ago.

Highquality paint will still look good outdoors after 7 years and indoors after 10 years.

6) Coverage. Painting over old paint can be challenging, especially if it: has a dark color,started to peel or crack or contains ingredients incompatible with your type of paint.

Be sure to select paint with more prime pigments like titanium dioxide (white pigment)which hides better and lasts longer than cheaper fillers like talc, clay, calcium carbonateor silica.

  • Once again, higher concentrations of solids will help fill voids and cover farbetter than low grade paints.
  • This information can also be located in the MSDS.

7) Cleanability and repairability. There are trade offs in sheen levels:

  • a glossier sheentends to resist marking and is easier to clean, but tends to highlight defects making themmore difficult to repair.
  • Flat or satin finishes, on the other hand, touch up easier, but arenot as durable or easy to clean.

Here is where the binders (see below) play their part andwhere your choice comes in.

For ceilings, flat sheen is most common because there is little cleaning and any ceilinglights won't reflect easily off problem areas. For the walls in bedrooms, living rooms andhallways, most people split the difference and go with eggshell because there is sometouch up and some cleaning. For the walls in kitchens, bathrooms and around windowsand doors, use semi-gloss or gloss, because there is where you'll have the most cleaningproblems with dirty little fingers.

8) References. Learn from the experience of others who have painted on similarsurfaces. Ask them what performs well over time and what doesn't.

Subtle differences inapplication can make major differences in paint performance. Also, paint manufacturersare constantly changing their formulas, so networking with other painters about what'scurrent can be very useful.

9) Warranty. Reputable companies stand behind their products and provide goodsupport if issues arise.

Longer warranties don't always mean the paint is better. After all,most manufacturers only replace the paint if there is a problem, and not the labor whichis the expensive part. Buy high quality paint from stores that turn inventory regularly andkeep good records of your purchases.

Where and how to do research on paint?

First, consult with the manufacturer's website to see where you can find information aboutingredients, pigments, binders and the percentage of solids contained in the paint.

Muchof this information can be located in the Material Safety Data Sheet (MSDS).

  • Here you'llalso find information about key ingredients especially their relative quantities by volumeand weight.
  • Why is this important?

Because the solids content is a good measure of quality. The more of it, the better thepaint, but also the more expensive it becomes. The solids content is what is left behindwhen the paint dries. A thicker film usually means a longer-lasting, more durable finish.But what is the content or ingredients of paint?

What is paint made of?

(The following has been drawn from Wikipedia)

  1. Pigments, such as titanium dioxide, and fillers
  2. Binders such as polymer resins
  3. Liquids such as diluents or solvents
  4. Additives such as thickeners, defoamers, wax, surfactants, UV absorbers, biocides, etc.

Pigments and fillers
Pigments are granular solids dissolved into the paint to contribute color. Fillers aregranular solids used to impart toughness, texture or to reduce the cost of the paint. Somepaints also include dyes instead of, or in combination with, pigments.

Pigments are classified as natural or synthetic. Natural pigments include clays, calciumcarbonate, mica, silicas and talcs, while synthetic pigments include engineered molecules,calcined clays, blanc fixe, etc. Hiding pigments make paint opaque and protect thesubstrate from the harmful effects of ultraviolet light. These include titanium dioxide,phthalo blue, red iron oxide and many others. There is currently some controversysurrounding the safety of titanium dioxide, which has replaced most toxic lead pigmentssince the late 70's.

Fillers are a special type of pigment that serve to thicken the film, support its structureand increase the volume of the paint. Fillers are usually cheap because they include inertmaterials such as diatomaceous earth, talc, lime, barytes, clay, etc. Floor paints that willbe subjected to abrasion may contain fine quartz sand as filler. Not all paints includefillers; on the other hand, some paints contain large proportions of pigment/filler andbinder.

Binders or resins
The binder, sometimes called a vehicle, is what forms the film or coating. The binderimparts adhesion, and strongly influences the sheen, durability, stain resistance, crackresistance, flexibility and toughness. In most cases, the higher the quality of the paint, thehigher the paint's ratio of binder to pigment.

Some typical binders include natural or synthetic resins such as acrylics, alkyds, vinyl-acrylics, vinyl acetate, polyurethanes, polyesters, epoxy or oils. Binders are categorizedaccording to the mechanisms for drying or curing. Drying means the evaporation of theliquid solvent or thinner, but it also refers to an oxidative cross-linking of the binderswhich is identical to the process of curing. Most paints dry through this cross-linkingprocess rather than through evaporation.

Latex paint is a water-borne dispersion of tiny polymer particles (binder). The
term "latex" in the context of paint refers to an aqueous dispersion and not the ingredientrubber (as it has been historically identified). Latex paints cure by a complex processwhere the water, and then the coalescing solvent, evaporate and fuse together the latexparticles. The resulting structure of paint is irreversibly bound into a network that will notre-dissolve in the solvent/water that originally carried it.

Manufacturers use many types of binders, depending on where and how the paint is tobe applied. Different binders can be used to improve the paint's resistance to moisturepermeability, sunlight exposure, damage from abrasion, adhesion to the surface andflexibility.In most paints, the pigment and binder solids account for between 25 and 50 percent ofthe total volume of the paint. The majority of the remainder of the paint's volume is theliquid carrier.

Liquids: diluent or solvent
The liquid portion of paint acts as the carrier for the pigments and binders. It is volatileand does not become part of the paint film when dry. It also controls flow (viscosity) andapplication properties of the paint.

In the case of water-based paints, water is the main diluent. In the case of oil-based oralkyd paints, the diluent can be made of organic solvents such as petroleum distillate,esters, glycol ethers or combinations of organic solvents such as aliphatics, aromatics,alcohols, ketones and white spirits.

Diluents help to keep the pigments and binders in suspension, but their primary functionis to reduce the cost of the paint. Higher quality paints have lower levels of diluents.

Additives
Paint can have a wide variety of miscellaneous additives, which are usually added insmall amounts, yet they provide a significant effect on the product. Some examplesinclude additives to modify surface tension, improve flow properties, improve thefinished appearance, increase wet edge, improve pigment stability, impart antifreezeproperties, control foaming, control skinning, etc. Other types of additives includecatalysts, thickeners, stabilizers, emulsifiers, texturizers, adhesion promoters, UVstabilizers, flatteners (de-glossing agents), biocides to fight bacterial growth and the like.Additives normally do not significantly alter the percentages of individual components ina formulation.

How do you tell quality paint?

Quality paints contain both the best pigments and binders, but in addition, they containmore of these solids than lower quality paints.

Economy paints provide hiding by using less pigment and extending it with fillers likeclay or calcium carbonate that will have good hiding capability initially but lose theirhiding capabilities over time--particularly when exposed to weather.

Prep, prime, paint

Finding the right paint for your application requires research and skill but once you'vefound it, your real job has just begun.

No matter how good your paint might be or howmuch you paid for it, it cannot succeed without proper preparation, priming and goodpainting techniques. Everyone knows that a good paint job is 50% prep and 50% paint.

  • Asmooth, dry, clean, neutral pH surface along with a good primer will provide the basis forgood adhesion and yield long lasting results.
  • Don't ask your paint to do your primer's job.

We will cover paint preparation and primers in another article.

For More Information:

Green Home Guide's Know How articlePaint Like a Green Progives practical tips for painting your home.

ReadSelecting Green Paintfor an overview of paint options and environmental and health considerations.