Paint is any liquid, liquefiable or mastic composition which is spread over a surface and dries to leave a thin decorative or protective coating. It covers the block work and concrete rendering (plaster) with attractive and beautiful colours, giving the building a high aesthetic value that makes it decorative clean and habitable.
Common Problems Of Paints In Nigeria
There are so many things that causes these problems, some of which I will discuss in this piece.
Alligatoring: this refers to a coating pattern that looks like the hide of an alligator. It is caused by uneven expansion and contraction of the undercoat. Alligatoring can have several causes: applying enamel over an oil primer; painting over bituminous paint, asphalt, pitch, or shellac; and painting over grease or wax.
Peeling: This is as a result of inadequate bounding of the topcoat with the undercoat or the underlying surface. It is nearly always caused by inadequate surface preparation. A topcoat peels when applied to a wet, dirty, oily or waxy, or glossy surface and must be sanded before repainting. Also, the use of incompatible paints can cause the loss of adhesion. The stresses in the hardening film can then cause the two coatings to separate and the topcoat to flake and peel.
Blistering: This is caused by the development of gas or liquid pressure under the paint. The root cause of most blistering, other than that caused by excessive heat is inadequate ventilation plus some structural defect allowing moisture to accumulate under the paint. A prime source of this problem, therefore, is the use of essentially porous major construction materials that allow moisture to pass through. Insufficient drying time between coats is another prime reason for blistering. All blisters should be scraped off, the paint edges feathered with sandpaper, and the bare places primed before the blistered area is repainted.
Prolonged tackiness: A coat of paint dries when it ceases to be “tacky’ to the touch. Prolonged tackiness indicates excessively slow drying. This may be caused by insufficient drier in the paint, a low quality vehicle in the paint, applying the paint too thickly, painting over an undercoat that is not thoroughly dry, painting over a waxy, oily, or greasy surface, or painting in damp weather.
Inadequate Gloss: Sometimes, a glossy paint fails to attain the normal amount of gloss. This may be caused by inadequate surface preparation, application over an undercoat that is not thoroughly dry, or application in cold damp weather.
Improper Application: This is usually controlled by the builder. It takes a lot of practice, but you should be able to eliminate the two most common types of application defects: crawling and wrinkling.
Crawling: Crawling is the failure of a new coat of paint to wet and form a continuous film over the preceding coat, this often happens when latex paint is applied over high gloss enamel or when paints are applied on concrete or masonry treated with a silicone water repellent.
Wrinkling: Wrinkling results when coatings are applied too thickly, especially in cold weather, the surface of the coat dries to a skin over a layer of un-dried paint underneath. Wrinkling can be avoided in brush painting, or roller painting by brushing or rolling each coat of paint as thinly as possible. In spray painting, you can avoid wrinkling by keeping the gun in constant motion over the surface whenever the trigger is down.
Chalking: Chalking is the result of paint weathering at the surface of the coating; the vehicle is broken down by sunlight and other destructive forces, leaving behind loose, powdery pigment that can easily be rubbed off with the finger. Chalking takes place rapidly with soft paints, such as those based on linseed oil. Chalking is most rapid in areas exposed to sunshine. In the Northern hemisphere, for example, chalking is most rapid on the south side off a building. On the other hand, little chalking takes place in areas protected from sunshine and rain, such as under eaves or overhangs. Controlled chalking can be an asset, especially in white paints where it acts as a self- cleaning process and helps to keep the surface clean and white. The gradual wearing away reduces the thickness of the coating, thus allowing continuous repainting without making the coating too thick for satisfactory service.
Checking and cracking: Checking and cracking are breaks in a coating formed as the paint becomes hard and brittle. Temperature changes cause the substrate and overlying paint to expand and contract. As the paint becomes hard, it gradually loses its ability to expand without breaking. This consists of tiny breaks in only the upper coat or coats of t h e p a i n t f i l m w i t h o u t penetrating the substrate.
The pattern is usually similar to that of a crow’s foot. Cracking is larger with longer breaks extending through to the substrate. Both result from stresses exceeding the strength of the coating. But whereas checking arises from stress within the paint film, cracking is caused by stresses between the film and the substrate. Cracking generally takes place to a greater extent on wood, due to its grain, than on other substrates. The stress in the coating is greatest across the grain, causing cracks to form parallel to the grain of the wood. Checking and cracking are aggravated by excessively thick coatings that have reduced elasticity. Temperature variations, humidity, and rainfall are also concerns for checking or cracking.