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Latex Paints Sometimes Stay Tacky
Dear NH,
During the rainy season our exterior doors stick and at times are nearly impossible to open. I am preparing to repaint them. After stripping and sanding, what is the best course of action to avoid sticking in the future? Do I prime/seal the doors first? Do I prime/seal all the edges? I've been told by some to prime/seal and paint the entire door, but by others to not paint the edges. I'm confused! Can you offer the solution. I will be using Benjamin Moore paints. Thanks
J
Dear J,
First, don't use latex paint. Latex paints are a marvelous invention for many reasons but, in some applications and under some conditions, gloss and semi-gloss latex paints can develop a "tackiness" that seems to last forever. I painted a garage door with an exterior latex paint over 5 years ago and, in the warm weather, I still hear the sound of the tacky paint breaking contact as the door goes up!
The problem you're having is known as "blocking", and can be caused by many factors such as applying an overly thick layer of paint, not allowing adequate drying between coats, reactions between the primer and the finish coat or the temperature at which the paint was applied... too hot or cold.
The best way to avoid blocking is to use an oil-based exterior alkyd paint instead. Alkyd paints, which are the very top quality oil paints, dry hard and smooth and do not produce the tackiness you have been experiencing.
Concerning your painting intentions, there are mixed views among painters on preparation for a latex-to-oil changeover. In my experience, oil paint can be applied over latex without priming as long as the environmental conditions are not too demanding. Of course, a light sanding OR the use of a "deglosser" such as Wilbond is essential for a firm paint bond.
In the case of an exterior door, though, I vote for (at the least) sanding followed by priming the doors prior to applying the oil. The primer must be an exterior grade and can be either oil or water-based. Again, there are some strong opinions on using either type of primer... just be sure it is an exterior grade. Under NO circumstances use Kilz, BIN, or any of the other interior primers.
Doors that are protected by an exterior storm door can have unique problems. Manufacturers of metal exterior doors generally frown on the use of storm doors, since the air space between the metal door and storm door can become hot enough under exposure to the sun to blister paint and distort the plastic mouldings that some companies use to mount the window glass! This can also occur with wood doors, causing the paint to prematurely fade or appear weathered. In fact, this overheated situation can even cause wood doors to expand and contract severely enough to cause cracks in the door panels! And guess what makes the situation even worse? You guessed it… dark pain colors!
A final comment concerning blocking… if you are not ready to repaint and would like to eliminate the tackiness, one method that I have used successfully is to apply auto or paste wax to the sticky area. The wax coating removed the tackiness, though it may have to be repeated occasionally if the tackiness reoccurs.
Dear NH,
A few months ago, I painted some built-in shelves with a few coats of semi-gloss latex paint. Even after all this drying time, the books and bric-a-brac still lightly stick to the shelves. In a few spots, the paint came off onto some of my collectibles. I am afraid something is going to be ruined by this paint problem. Please help!
MP from Boulder, CO
Dear MP,
I have talked about this problem before and I am sure that, until the latex paint manufacturer's figure out a way to solve it, I will be doing so again!
Latex paint, due to its chemical nature, can retain a certain amount of "stickiness" for a long period of time after it dries. This residual tack is known in the latex biz as blocking. Though all latex paints, interior and exterior, have anti-blocking agents added to them, the final results are mixed. How much blocking you will experience with a given paint job is related to various factors… the number of coats you apply, the thickness of the paint coats, the temperature and humidity in the room, how well you mixed the paint, and the manufacturer.
Blocking is not a consideration with walls and, in most circumstances, doors and trim. One problem is that exterior doors painted with latex paints are notorious for sticking to their weatherstripping. I always advise against using latex paints for surfaces that will be in regular contact with anything. In sympathy with your plight, I too have seen books lightly sticking to latex-coated shelves after years of drying!
Though there are "prophylactic" solutions, such as waxing the shelves or dusting with talcum powder, the best and most permanent solution is to repaint the shelves. The paint of choice for shelves and cabinets is a high quality alkyd paint. Alkyd is the best of the oil-based paints, drying to a hard, non-tacky surface every time!
My advice is to lightly sand the shelves with a fine (220 grit) sandpaper, then give them a complete coat of a fast drying primer… you can use a latex PRIMER such as Zinnser 123 if you want. The primer is important… alkyd oil directly over latex FINISH PAINT is not advisable. Then apply one or two coats of a matching alkyd paint in either gloss or semi-gloss. If you are a careful painter, you can probably just paint the top surfaces of the shelves… it will save you some work! Once dry, your sticking problems will be gone forever.
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