Paint, Stain, Alkyd, and Acrylic? Help!

If you have ventured into a hardware or paint store lately, you may have noticed that there are a million different paints and stains available. As with any project, homeowners are often inundated with material choices and conflicting advice. Sometimes, advertising can be misleading, and there are definite no-nos to be wary of when choosing materials for any given project. Which product is best for a particular job can be difficult to sort out. Let me give you a few pointers which should help you choose the right product for your job.

Lets talk only about exterior painting. On the Outer Banks, there are a large number of homes in varying degrees of upkeep, the worst of which have been neglected, improperly coated, or treated with the wrong materials, causing premature failure. Don’t let this be you! A good coating job here should last at least five years. If you are not getting that, you may not be using the correct material for your substrate.

Even the best coating will not perform properly if applied incorrectly. 95% of all coatings failures result from improper application of the coating! You must ensure that your substrate is clean, dry, and sound (not rotted). With these issues are covered, lets choose the right coating for your job, starting at the beginning, with primers.

The substrate that most commonly has coating failure is wood, both siding and trim. This is mainly due to the number of types of wood and varying degrees of soundness of the wood.

First, I would suggest that you check the wood for any signs of rot that might be present. Poke around with a pencil in some of the areas that stay moist longest. If your pencil goes through then the wood, or even partially through, it needs to be replaced.

Next, determine which type of wood you are dealing with. For the purpose of our discussion, you will only need to know if the wood is pressure treated or Cedar. Cedar is the most commonly used type of wood for siding and trim here on the Outer Banks. This is because Cedar has the highest concentration of natural oils, or tannin in the wood. This tannin resists rot more so than woods with little or no tannins at all, but when coated, this attribute can pose problems of its own.

If you are coating Cedar you will need an oil based primer that dries slowly and has tannin block ability. If untreated, the tannin in the wood will seep out over time, causing discoloration and staining of your newly coated surface.

I specify oil primers because the molecules of oil (or alkyd) primers are much smaller than those of comparable latex (water based) primers, which allow the material to penetrate deeper into the wood providing you with superior adhesion. Before applying this primer, however, you will need to evaluate the product to determine its viscosity. Many of the best products in this category are very thick and will need to be thinned down so that penetration can occur.

When a very thick primer is applied over wood, very little penetration occurs, leaving most of the product on the surface with very poor adhesion as the substrate expands and contracts.

If this is the case with your chosen product, use some clean paint thinner (mineral spirits) to get your primer to the point where it will penetrate deeply, do not worry about complete coverage yet. Thin is good in this instance, contrary to popular belief.

Also, as tempting as they can be, do not use fast drying primers for this application because they dry much too brittle and will crack and fail within one year as the hot/cold cycle works its magic. Many people find the quick drying materials attractive because they can be finish coated the same day, but for our environment, the substrate expands and contracts too much for a brittle primer.

The second most common type of wood you may be dealing with is Pressure Treated lumber. This can be identified by a green hue, and a stamp on the wood itself. Most commonly used for railings, decking, and support posts, PT lumber is sometimes used for window and door trim too. If your PT lumber is brand new, I strongly recommend leaving it untreated for at least six months so that it cures properly.

When PT lumber is manufactured, it is permeated with arsenic and stacked for drying. As soon as it stops dripping, it is on the shelves of your lumber yard for sale. While this lumber may appear dry and read under 15% moisture on a moisture meter, it is certainly not cured and will continue to leach the arsenic from within for up to 18 months as it cures.

When painted prior to this curing, frequently the paint will peel as the chemicals try to work their way out of the wood. This has been the topic of many a debate on the Outer Banks and painters have bared the brunt of the responsibility for this peeling, but now you too can consider yourselves educated.

The one exception to this rule is PT that is marked KDAT, or Kiln Dried AFTER Treatment. Very few contractors use this lumber as it is more expensive, but if you are one of the lucky ones, you may successfully paint this immediately.

For PT lumber, the best primers are latex, and very often do dry quickly. Make sure that the primer is for exterior use. PT lumber does not have nearly as much tannin to be concerned about, as pine is used most often, but you do need a primer that has stain killing abilities for the knots, and offers good adhesion. Look for those two attributes on the labeling.

Sometimes you will need to use two coats on the knots to prevent tannin bleed. PT lumber differs from Cedar in that PT lumber is much smoother and sometimes has a mill glaze that these latex primers address much better than the alkyd alternatives.

Penetration is diminished by the mill glaze and the chemical content of the wood, so go with the latex alternative. Mill Glaze is a condition that is brought on by the milling process whereby the wood can have a shiny appearance which prevents any coating from penetrating the surface.

If you notice this condition, a light sanding will pay off for you in the long run. Just sand enough to rough up the surface a bit, nothing too strenuous.

Some of the other substrates used commonly for the exterior of homes are HardiPlank cementatious siding, vinyl, and aluminum.

In most instances, these substrates do not require a primer and can be coated with a good quality 100% acrylic paint. Of course, you will need to ensure that all surfaces are clean, dry, and free of organisms first.

While that probably covers all of the pertinent exterior substrates, you may be dealing with an existing home that is peeling. I often find that homeowners with this problem are ill advised on the proper methods to repair this condition. Unfortunately, most painting contractors will not completely address this issue with the owner, if at all, and the result is a never ending cycle of touch-up and repainting due to continual peeling.

Peeling paint can be repaired so that this does not recur, although in most cases it is not cheap. If you have a peeling problem, the peeling areas should be stripped to remove all of the old coating, even if it does not appear to be peeling now. This is especially true in the case of shake shingles. Often a contractor will specify a scope of work which includes pressure washing first then painting. Pressure washing alone will not remove enough of the defective coating to ensure that the remaining areas will not peel in the future. Any coating left will usually continue to peel for years to come ruining any new paint work.

I have personally spent many hours on this problem trying to educate my fellow painters and my customers on this issue and I can say with great authority that there is only one way to permanently fix this problem.

On to finishes… Finish coat products also come in many forms. By understanding the factors involved in the deterioration of each finish, you can easily make the appropriate selection.

Generally speaking, as long as you have properly prepared and primed the substrate, the biggest factor that will cause a finish coating to fail prematurely is UV light.

The sun will dry out a coating and over time will cause a condition called chalking. You may notice this on your home if you rub your hand on the surface and the coloring appears on your hand. At this point, the coating will actually retain moisture instead of repelling it and will deteriorate more rapidly as time goes on.

When choosing a finish coat for any surface, use quality material, which will pay for itself in the long run. I recommend using a product that has a sheen, which will reflect UV light better that flat paint or stain and will last longer.

These sheens come in varying degrees of reflectivity and price, of course. Latex stains are best on wood siding and should provide you with the longest lasting jobs.

Most exterior latex stains available today come in a flat finish. There are latex exterior stain products that have a sheen, but you will have to do your homework and ask for them.

For pressure treated lumber, as well as the other substrates that I mentioned, paint will serve you best. Use latex paints that are labeled 100% acrylic, as they are the best product available today and easily found at any paint store. Latex paints and stains also resist UV light deterioration much better than oil based comparables.

The biggest difference between paint and stain is the consistency and the solid content of the material. Paints are usually much thicker than stains and have a higher solid content. The higher the solid content, the longer the material will last.

Finally, consider using the new generation ceramic coatings. These products usually offer superior warranties which cover defects in labor and materials, but usually can only be applied by certified contractors. These products offer the best in protection for all substrates but will cost more initially.

Material choices can be confusing, but stick to these guidelines and you will make better informed decisions. I always recommend that if you are not sure what to do, call a pro. Good luck!