“We learned over years of house painting practices that paint peels for a variety of reasons. Before we paint, we first figure out why an area is peeling. Once we identify the cause of peeling, we can eliminate it and thus ensure that our next coat of paint will last long into the future.”-Goldenland House Painters.
Blisters are dome like protrusions in the paint coat, like blisters in human skin. They are caused by water that is caught between the paint and the wood which in common in Auckland house conditions, due to the unique weather of both strong sun shine and heavy raining. When the water expands, the paint skin is forced off the wood. There are several ways in which water may be trapped. The paint may have dried too quickly. Painting in the sun or on a hot surface causes the elements in the paint to heat up, and its ingredients may separate and vaporize, creating small vapor pockets. These pockets reduce the paint’s ability to adhere to the surface. Moisture may penetrate the wood from the other side. Bathrooms, interior water pipes, and leaky gutters are possible sources.
Moisture passes through the wood and becomes trapped beneath the paint layer, causing blisters. An oil-based paint tends to blister if used on a moist surface. Oil and water do not mix, and this moisture remains trapped between the surface and the paint. When the moisture vaporizes, it pushes the paint off the surface. Before painting, we remove all sources of moisture, we replace old caulk and weather stripping, check if pipes and gutters are watertight, and we seal cracks in the painted surface.
When painting, the precautions are straight-forward. We do not paint in direct sunlight or on a hot surface, such as an area that has just bathed in hot sun. We then allow the surface to cool before painting it.
Of course, surfaces are completely dry before painting. The drying time may be as little as an hour if the surface is in the sunshine, or a day or more if the surface is shaded.
True to its name, this condition looks like the skin of an alligator. Paint contracts, flakes, and falls off in rectangular chips. Watch for the gradual growth of small vertical and horizontal cracks in the dried paint. These are often the harbinger of alligatoring. Alligatoring is most common on older homes because of the thicker oil paints that were once used.
There are three conditions that favor this problem in Auckland.
- It is apt to strike when glossy paint is applied over a glossy surface. That’s because the glossy surface is so smooth that the new coat of paint has trouble gripping it. This allows the new paint coat to shift back and forth, causing it to crack and fracture. Prevent the problem by lightly hand sanding glossy surfaces with 50-grit sandpaper.
- Alligatoring also may result if a second coat was applied before the first one dried completely. The second coat of paint cuts off the airflow to the first coat and keeps it from drying. This still-soft first coat then expands and contracts with temperature changes, cracking the upper layer. So, allow each coat of paint to dry completely before re-painting. That takes from 4 to 8 hours for latex paints and 24 to 48 hours for oil paints, depending on factors such as humidity, temperature, and exposure to sunlight. You can eyeball a painted surface for dryness by looking for varying shades of paint; dry paint will be a uniform shade. Press a finger-nail into wet-looking spots: if the paint is still sticky and pliable, allow more drying time.
- Paint may alligator if applied too thickly. To prevent this, be sure that each coat is brushed on evenly.
Cracks begin as barely noticeable splits in the coat of paint, then become longer and wider. The process may continue until the paint alligators or begins to curl off the surface. On wooden surfaces, cracks usually run with the wood grain.
The natural expansion and contraction of wood can lead to cracking. When its fibers absorb water, the wood expands like a sponge; when the water is given up, the wood contracts. Green, unseasoned wood is especially vulnerable. This movement pulls the paint apart and creates cracks. Movement is also a problem on surfaces that are flexed, such as garage doors.
We make sure wooden surfaces are kept fully painted, stained, or otherwise protected from water. We use kiln dried lumber when building and renovating, rather than green wood. There is little you can do to prevent cracking caused by motion stress, other than fully stripping the surface and repainting with a high-quality paint.
Cracks also occur because paint loses its elasticity with time. Even though I say paint “dries” within 48 hours at most, paint does not completely dry for months or even years after application, because it is formulated to retain a degree of elasticity that will resist many stresses. As this flexibility is lost, cracking may appear.
Thus, the only prevention is to prepare the surface well and to use a top quality paint. An inferior paint may encourage cracking.
Flaking and Peeling
Flaking and peeling are catchall descriptions for paint problems. They are caused by any of the reasons mentioned above: moisture, brittle paint, sunlight exposure, uneven thickness, and so forth. Pay attention to these factors and you will minimize chances of peeling and flaking.
Peeling on Brick
Paint may blister and flake on brick for a few reasons. Chemical reactions between the brick and the mortar produce mineral crystals that can push paint off the brick. To prevent this, we wash the minerals from unpainted brick with a solution of 15 percent muriatic acid and 85 percent warm water. This acid solution can burn your skin and damage your eyes, so wear rubber gloves and goggles when washing. For painted brick, we wash with TSP and bleach. Then we allow the brick to dry, scrape off loose and peeling paint, then repaint: first spot paint the scraped areas, then paint the entire wall.
Trapped moisture may push against the paint and loosen its grip on the brick. Simply be certain that the surface is dry and cool when painting. Moisture may be seeping through a chink in the masonry from the other side, so check for its source on the inside of the house. Also examine gutters and downspouts for leaks.
If the brick or mortar is deteriorating, the paint will surely fall apart as well. You can tell if you have a problem if the backsides of the paint chips are choked with mortar and brick. The wall may have to be repointed with mortar or rebuilt.
Sags and Drips
A sag is a wavy, horizontal line of excess paint. Drips are simply drops of paint headed downward. Both are the result of sloppy workmanship and putting on too much paint. We check our painting work 15 minutes or so after you apply the paint and use a brush to smooth out any flaws before they dry. Sags and drips are the trademarks of a lazy painter, NOT us from Goldenland House Painters.
Nail Head Stains: Rusting nail heads can be sanded to bare metal, then dabbed within 1 hour, preferably with a rust inhibition paint. When this paint has dried, apply the finish coat.
Lap marks are spots that are slightly different shades than the rest of the painted or stained surface. They spoil the color and sheen consistency of an otherwise good job. They are a particular problem with oil stain, although you can also get lap marks of sorts uneven gloss when using high-gloss paints.
Lap marks most often occur when stain is only partially applied over a surface. For example, picture yourself staining a long board. You’re halfway done staining it, but it’s lunchtime and so you stop staining to eat. An hour later you resume staining. A lap mark will appear at the last spot you stained before lunch. The remedy is to not take a pause from staining until you bring the stain to a visual break in the siding or shingles—a seam, a joint, a split, or the end of a wooden piece. When you resume working from that break, be careful not to get any stain on the finished side of the break, or the over-lapped area will look shiny and as if it were a different color. Another cause of lap marks is an uneven application; thicker stain will dry more slowly, creating a slightly different tone and sheen.
A third possibility is that a change in surface texture will show up as a lap mark, because rougher boards absorb more paint or stain. When one coat does not provide enough pigment to give a consistent color across an area, apply a second coat. Should this fail to work, we sand down the rough wood and start over.
Chalk is a dry and usually whitish powder that appears on flat paint over time. In simple terms, as paint deteriorates, it wears off the surface in the form of chalk. Chalking actually has a benefit: during rainstorms, it helps to carry away dirt from the paint surface, leaving the house looking fresh and clean. Chalk is a problem only when it is excessive: it dulls the paint’s color and can discolor lower boards and brick. You cannot stop chalking once it begins, but we can safely paint over chalking surfaces.
Mildew is a fungus that grows in, under, and on top of paint and stain. It feeds on organic substances in paint and stain, and given the right environmental conditions of moisture and shade, it will continue growing until entire walls and ceilings are blackened. Mildew ruins color tones and can cause unpleasant odors.
From a distance, mildew resembles dirt. Look closely, however, and you can see small lines branching out from tiny circles. A good test for mildew is to put a few drops of household bleach on the dis-colored area and wait a few minutes. Do not scrub. If the discoloration disappears or fades, then the splotches are mildew; if the splotches are not bleached out, the discoloration is most likely dirt.
We wash the mildewed area with bleach. I use a fifty-fifty mixture of water and bleach, and add 2 cups of TSP per gallon of solution, which is stronger than the recommendation on the TSP label. This is a potent brew, so use rubber gloves and goggles. Using a dustpan brush, wipe the area with the solution, drenching all affected areas. You need not scrub: the solution will do the work. The bleach kills the mildew and TSP acts as a soap to cleanse the surface. Rinse the area with a garden hose until the runoff is clear, and allow it to dry before painting.
We do not apply paint or stain over mildew The fungus feeds on ingredients in these finishes, so you can imagine how quickly it can spread if it finds itself sandwiched within layers of food. Once mildew gets under the finish’s surface, TSP washes will kill only the surface growth, allowing the under-lying mildew again to eat its way to the surface. The only way to stop mildew inside the paint is to sand the surface to bare wood and repaint.
Most exterior paints and stains are mildew resistant. Interior paints formulated for bathrooms and kitchens also contain mildew inhibitors. Paint stores carry vials of mildew preventatives that we can stir into oil or latex paint intended for use in moist, shaded areas.
Over time, paint loses its gloss, brilliance, freshness and appeal. The cause is natural aging, which cannot be prevented. We try bringing the appearance back with a TSP wash. But the only way to recapture the old shine is to repaint.