Painting is an important finishing work that is necessary to increase the aesthetic value of any structural construction. Besides, painting also provides an outer protective coat or layer to the structure from various atmospheric factors such as frost, sunlight, rainfall and so on as well as from various infiltrative actions such as corrosion, decaying, weathering etc. In the absence of regular maintenance and the use of poor quality of paint may lead to the rise of defects in painting.
Defects In Painting
Some of the defects in painting work can be summarized as follows:
Fading is a common type of defect in painting work which causes the discolouration of the applied paint.
The main causes of such defect are the various atmospheric factors such as rain, sunlight, moisture infiltration etc.
Precisely, fading may be defined as the loss of one or more colour pigments from the film of paint.
Over time, the film of paint starts to lose the colour pigments under harsh atmospheric conditions and continuous sun exposure.
Causes of Fading
The main causes of fading can be listed as below:
1. Sunlight, Infrared and Ultraviolet Radiation
2. Temperature Variations
3. Application of dark colour paints (darker colours tend to absorb more radiations from the sunlight)
4. Coastal and Harsh Environmental Conditions
5. Inadequate Film Thickness
6. Use of inferior quality paints
Repair & Prevention of Fading
Once fading of the paint coat begins, it cannot be repaired completely but for preventing further de-colouration, weathering resistant pigments may be used.
Some of the precautions that can be taken to prevent fading can be listed as follows:
1. Use of certified UV resistant paints from authorized manufacturers.
2. Selection of lighter coloured paints.
3. Regular maintenance and supervision.
ii. Peeling and Blistering
Blistering of paint is a defect that causes swelling of the paint film.
The actual reason behind the swelling of the film of paint is the formation of air bubble beneath the coating of paint due to the ingress of moisture, oil or grease matter.
If the swelling of the film of paint occurs due to grease or oil then it is known as blistering.
On the other hand, if the swelling of the paint film occurs due to water or moisture it is known as peeling.
Usually, the swelling is caused due to the use of excessive oil during the application of the final coat, inappropriate seasoning of timber, trapping of gases beneath the coat of paint etc.
Causes of Feeling & Blistering
Some of the causes of peeling and blistering of paint can be listed as follows:
1. Excessive moisture
2. High humidity
3. Excessive layers of paint
4. Lack of surface preparation before application
5. Use of poor quality paint
6. High temperature
7. Long exposure to sunlight
8. Use of inappropriate application technique.
Repair & Prevention of Peeling & Blistering
Such defects can be prevented by using porous paints such as emulsion paints instead of non-porous paints. The coat of paint subjected to excessive peeling and blistering can be repaired as follows:
1. First of all, the working space must be cleared. All the furniture and utilities must be covered.
2. Then, the area of paint coat where peeling has occurred must be scraped off using a wire brush or paint scraper.
3. The surface is then prepared for the application of a new coat which includes plastering of cracks if any, cleaning of the surface etc.
4. An appropriate primer is then applied on the prepared surface.
5. The final coat of paint is then applied.
Running of paint is a type of defect in painting work that occurs when the surface of the paint is too smooth. In this type of defect, due to excessive smoothness, the paint runs back leaving behind some uncovered surfaces.
Causes of Running
Some of the causes of the running of paint can be listed as follows:
1. Low viscosity
2. Excessively glossy surface
3. Application of too wet paint
4. Irregular spraying action
Repair and Prevention of Running
Such type of defect can be prevented by the use of appropriate spraying technique, use of smaller nozzle etc. The repair work includes the following steps :
The paint is first allowed to dry completely.
After it has dried completely, the run is removed with a wet sandpaper, carbon block or sand block.
Then, the surface must be finely polished and compounded.
The surface is finally treated with high-gloss polish.
In the absence of adequate thickness of the final coat of paint, the background becomes visible. Such defect is known as grinning of paint.
Precisely, grinning occurs when the paint coat is not opaque enough to cover the background i.e. due to insufficient opacity of the final coat of paint. Thus, the underlying surface becomes visible.
Causes of Grinning
Some of the causes of grinning of paint can be listed as follows:
1. Inadequate thickness of the final coat
2. Insufficient volume of paint
3. Low opacity paint
4. Use of strong colour in underlying coats
Repair and Prevention of Grinning
This defect can be prevented by ensuring the use of adequate thickness and volume of the final coat. The repair work includes the following:
1. The grinned surface is first thoroughly cleaned.
2. Then, another paint that is compatible with the grinned surface is
selected and duly applied to the defective surface.
Sagging is associated with the application of a thick layer of paint on an inclined or a vertical surface. It is the type of defect in which the layer of paint applied falls downwards i.e. sags down from the surface.
Causes of Sagging
Some of the causes of sagging of paint can be listed as follows:
1. The excessive thickness of the coat
2. Poor workmanship
3. Lack of surface preparation
4. Inappropriate spraying technique
5. Low viscosity
Repair and Prevention of Sagging
Such a defect can be corrected by the following steps:
1. When the paint is still wet, it is rolled out or brushed out immediately to cover the surface evenly. If the paint has already dried, it must be removed using sandpaper and a new coat must be applied.
2. The painting must not be carried out during cold weather or humid conditions.
Chalking is the type of defect that results in the formation of powder-like substances on the surface of the paint.
The main reason behind the chalking of paint is the use of insufficient oil in the primer.
Causes of Chalking
Some of the causes of chalking can be listed as below:
1. Use of inferior quality paint
2. Long exposure to sunlight and ultraviolet radiation
3. Use of correct film thickness
4. Alternate hot/cold temperature
Repair and Prevention of Chalking
Once chalking occurs it cannot be undone. To eliminate the defect, the surface must be pressure washed or scrubbed to remove the surface contaminants. Some of the preventive measures that must be adopted to prevent chalking are as follows:
1.Use of water-based paints
2. Use of lighter shades of paint
3. Regular maintenance
The type of defect in which the paint film detaches from the surface is known as flaking of paint. In general, flaking may be understood as the phenomenon in which the paint coat does not stick properly on the surface.
The main reason behind the flaking of paint is the lack of adequate bonding between the surface and film of paint.
Causes of Flaking
Some of the causes of flaking can be listed as follows:
1. Poor paint adhesion
2. Inadequate pre-cleaning before application
3. Ingress of moisture
4. Use of inferior quality paint
Repair and Prevention of Flaking
To prevent the flaking of paint, the surface must be first cleaned properly and rubbed by an abrasive paper before the application of paint. The flaking of paint can be corrected by following the below-mentioned steps:
1. Firstly, the flaked surface must be examined and thoroughly
2. The surface is rubbed using sandpaper.
3. Then, the surface is treated with a prime coat.
4. Finally, the surface coat is applied.
Blooming is the type of defect that causes the formation of dull patches on the surface. Blooming of paint results in the appearance of the whitish patch on the outer surface of the paint.
Generally, water is collected after condensation and the water-soluble compounds migrate to the coated surface from the body of paint. When such molecules evaporate from the surface, it results in the formation of a dull patch.
The main cause behind the blooming of paint is the poor quality of paint and improper ventilation.
Causes of Blooming
The causes of the blooming of paint can be listed as follows:
1. Use of fat thinners
2. Excessive humidity level
3. High air pressure
4. Poor workmanship
5. Use of inferior quality paint
6. Poor air movements
Repair and Prevention of Blooming
The preventive measures for avoiding the blooming of paint can be listed as follows:
1. The temperature must be maintained at 68 degrees F to 78 degree
F as far as possible.
2. Use of good quality paint, retarder, thinner etc.
3. Reduction of air pressure.
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