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Understanding Paint – Painting Tips

Just today, I received an email from an individual who had an exterior paint job fail after just six months! That is miserable performance. The email contained lots of voodoo excuses and solutions from the painter and a carpenter buddy. Neither, in my opinion, had nailed the cause of the problems. Based upon the description in the email, it appears that excessive indoor humidity is to blame. I never cease to be amazed at the amount of bad information that is out there.

My newspaper this morning had a feature article in it about cleaning and sealing decks. All of the information given in the article was suspect. Seriously! The reporter had called some local deck cleaners and took their word as gospel. All I am trying to say is watch where you get your information.

Paint is a Film Former

Paint, by its inherent nature, is designed to peel. It is a film forming coating. Paint will stick very, very well to substrates that do not move too much. Examples of this are just about any metal. Think. When was the last time you saw paint peel from a refrigerator or stove? Do you think it is because they use special high tech paints? Not really. Metal of just about any type is an excellent substrate. It doesn't move too much. Aluminum siding is a good example. Paint can last for years on aluminum. Aluminum expands and contracts, but the paint holds on!

Wood is the WORST!

Wood is just about the absolute worst thing to paint. It expands and contracts wildly in response to changes in moisture content. This movement can easily defeat the strongest paint film.

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Some wood products such as hardboard or Masonite® must be painted multiple times on all edges and sides to protect both the material and the finish paint film. Hardboard can swell enormously if it gets wet. The paint is the only line of defense. If cut edges and seams are not painted during installation, you can have severe rot develop within a matter of just a few years. When was the last time you saw a carpenter have a can of paint open near a miter box or circular saw? To the best of my knowledge, I was one of just a handful of carpenters in Cincinnati that carried paint/primers alongside my saws!

Shrink Wrap Your Wood

Wood will behave and paint will stick quite well if you can paint the entire piece of wood before it is installed. The old-timers called this backpriming. It can be done assembly line fashion in the field. You can also buy many wood sidings and trim that come factory primed. This is a must if you want a long lasting paint finish on your new home or room addition.

Sealing the wood completely means painting cut edges as well. This will be a hard thing to get your carpenters to do. However, it is absolutely necessary. The cut ends are often where end grain is exposed. End grain is where water has the easiest time entering wood. Water that is sucked up by end grain will liberate itself five or six inches away from the end of the board. This is why you often see the butt edges of wood siding peel or the bottom portion of trim boards flake.

Flexible Paints

Knowing that wood moves, it would help to have primers and paints that have built-in flexibility. Acrylic resins (resin = paint glue) are the ones with the greatest amount of flexibility. The paint can resist years of movement. It appears that these paints will not get brittle like the older oil based paints.

Exterior house paints can contain other resins or glues. They do not perform as well as acrylic resins. Keep in mind that once the paint dries you are left with only two of the three primary ingredients in paint: the resin and any color pigments. It pays to purchase the absolute best resin or glue that you can afford! Acrylic is the best - plain and simple.

Related Articles:  Exterior Home Painting & Weather, Exterior Painting

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