Construction & Materials II - Paint Notes
Paint
What is Paint?
Paint is a pigmented liquid, liquefiable, or solid mastic composition that converts to a solid film after being applied to a substrate in a thin layer.
Paints are typically oil-based or water-based.
Types of Paint
Oil Based Paint
Oil paint is a slow-drying paint consisting of pigment particles suspended in a drying oil, commonly linseed oil.
The viscosity can be modified with a solvent like turpentine or white spirit; varnish can be added for increased glossiness.
Typically applied as a primer, undercoat, and finish coat.
Historically favored for durability and longevity, but water-based paints are now comparable.
Known for gloss, water resistance, and long-lasting qualities.
Applications, Benefits, and Tips:
Use on metals, walls, doors, windows, and stained surfaces for durability.
Highly recommended for trim work.
Use in non-humid areas due to longer drying times (over 24 hours).
Easy to clean and apply.
More likely to emit VOCs (volatile organic compounds), which are linked to health issues.
Enamel Paint
An oil paint that air-dries to a hard, usually glossy, finish.
Used for surfaces exposed to hard wear, temperature variations, or outdoor conditions.
Shares key qualities with oil paints, such as slow-drying abilities and hardness.
More expensive but offers high durability, strong adhesion, glossy finish, and water/stain resistance.
Applications, Benefits, and Tips:
Perfect for humid/wet spaces like bathrooms and kitchens, and on metals.
Best for walls needing protection.
Popular for woodwork, metalwork, and window work.
Offers good coverage, hardness, and color retention.
Long-lasting for certain wood and metal surfaces.
Bituminous Paint
Special paints used in construction for waterproofing, corrosion resistance, and damp proofing.
Made from bitumen or coal tar dissolved in mineral spirit or naphtha; applied in liquid or semi-liquid form.
Waterproof but generally not suited for sun-exposed areas due to deterioration.
Pigment can be added for color.
Bitumen is a dense, viscous, petroleum-based hydrocarbon found in oil sands, pitch lakes (natural bitumen), or as a residue of crude oil distillation (refined bitumen).
In the US, bitumen is often called asphalt.
Applications, Benefits, and Tips:
Provides a protective, waterproof, weatherproof, chemical, and corrosion-resistant layer.
Ideal for metalwork, pipework, woodwork, and underwater structures.
Ideal for exteriors such as ladders, shafts, and other ironwork.
Helps provide rust resistance for metal applications.
Aluminum Paint
Coating material made from a mixture of oil varnish and aluminum pigment in thin flakes.
The overlapping flakes reflect the sun's radiation and retain heat in hot-air or hot-water pipes/tanks.
Resin helps the paint flow and provides strength/durability; aluminum flakes give a shiny, metallic finish.
Typically has a silvery finish.
Applications, Benefits, and Tips:
Used for hot water tanks, hot pipes, masonry, oil storage tanks, etc.
Used for metals and woods.
Popular for being electricity and corrosion-resistant.
Waterproof.
Water Based Paint
Also called latex paints; consist of pigment and binder with water as a carrier.
Emulsion, satin, gloss, and matte paints are often water-based.
Great for interior walls, windows, doors, and painting skirting boards.
Applications, Benefits, and Tips:
Typically dries much quicker.
Easier to apply with a brush or roller.
Low odor and more environmentally friendly.
Emulsion Paint
Water-based paint containing small polymer particles with pigments inside, suspended in water.
After drying, the particles combine to produce a paint film.
Fast-drying.
Popular for paint contractors because it's alkali-resistant, rich in texture, and has strong color retention.
Two common types: matt and silk.
Matt: very low sheen, reflects little light, ideal for ceilings and imperfect walls.
Silk: higher sheen, more durable and washable than matt, but shows imperfections more easily.
Applications, Benefits, and Tips:
Mold and mildew resistance.
Low VOCs, making it a good non-toxic choice.
Easy to apply on exterior and interior walls.
Offers a range of wall finishes like satin, eggshell, glossy, matt, etc.
Emulsion-painted walls are easy to clean.
Anti-Corrosive Paint
Composition of corrosion-resistant pigments such as zinc chromate, lead chromate, zinc oxide, zinc dust, or red lead.
Linseed oil is used as a binder.
Used for preservation of structural steelwork against acid fumes and adverse weather conditions.
Protects metal components against degradation due to moisture, salt spray, oxidation, and exposure to weather conditions and industrial chemicals.
Synthetic Rubber Paint
Made from polyvinyl material, formulated from dissolving synthetic resins and adding pigments and solvents.
Any color can be attained due to added pigments.
Used on concrete surfaces, walls, and floors because it's weather-resistant.
Applications, Benefits, and Tips:
Dries very quickly and maintains consistency/uniformity on large expanses.
Cost-effective, chemical-resistant, and weather-resistant.
Widely used on concrete walls, large surfaces, floors, grounds, etc.
Long-lasting despite weather and wear/tear.
Cement Paint
Traditionally known as whitewash or cement paint.
A mixture of portland or white cement and lime with additions of mineral extenders, accelerator, and water-repellant substances.
One of the oldest types of paint.
Applications, Benefits, and Tips:
No cracking due to sunlight.
Can be applied on cement and rough interiors/exteriors without primers.
A cheaper medium of paint and application.
Paint Finishes
Gloss and Semi-Gloss
Gloss has a very high sheen; semi-gloss has a slightly lower but still high sheen.
Gives a luxurious-looking finish.
Typically used for wooden trim like skirting boards, door frames, doors, and windows, but can be used on walls as well.
The best gloss paints produce a hard-wearing finish that is easy to clean.
High sheen means it reflects a lot of light and will show up surface imperfections.
Satin
Mid-sheen gloss paint; finish between matt and gloss.
Less reflective surface means it shows fewer imperfections and creates a more subtle finish.
Typically durable and wipeable.
Eggshell
Low sheen, but higher than matt paint; finish similar to an eggshell.
Similar in appearance to satin but typically has a slightly shinier sheen.
Matte
Sometimes called flat; low gloss percentage, meaning it doesn't reflect much light.
Excellent for hiding surface imperfections.
Has a lot of pigment, making it quick and easy to apply to more extensive surfaces.
Paint Systems
Primer
A preparatory coating put on materials before painting (also called undercoat).
Ensures better adhesion of paint to the surface, increases paint durability, and provides additional protection for the material being painted.
Finishing Coat
The final layer applied in a coating protection system.
Enhances aesthetics and environmental protection.
Enhances the corrosion protection of a material by ensuring added resistance.
Paint Defects
Blistering and Peeling
Defects in which swelling of the paint film occurs.
Swelling is caused by the formation of an air bubble under the paint film due to the presence of moisture, oil, or grease.
If due to moisture, it's called peeling; if due to oil/grease, it's called blistering.
Occur due to imperfect seasoning of timber, usage of excess oil in final coat, imprisoned gases between paint coats, etc.
Can be eliminated by using porous paints like emulsion paints instead of non-porous paints such as oil paints, enamel paints, etc.
Fading
Discoloration of the paint surface.
Mainly due to atmospheric agencies such as sunlight, moisture, etc.
To prevent fading, use weathering-resistant pigments in the paint.
Grinning
Visibility of the background due to insufficient opacity of paint film, even after the final coat.
The paint film should be opaque enough to cover the background surface.
Chalking
Formation of powder on the painted surface.
Due to the use of insufficient oil in the primer.
Prevent by using sufficient oil in the primer and applying paint at the recommended spreading rate.
Running
When a thin layer of paint is coating on a glossy and smooth surface, the paint may run back and leave small areas of the surface uncovered.
Sagging
When a surface is painted with a thick layer of paint, the thick paint film may run downwards and form sagging of paint.
Similar to running, but the sag of paint is very thick.
Flaking
Detachment of paint film from the surface.
Occurs when the bond between surface and paint film is poor.
Prevent by cleaning the surface and rubbing it with abrasive paper before applying paint.
Blooming
Defect caused due to improper ventilation, weathering, defective paint, etc.
Dull patches are formed on the painted surface.
Saponification
Occurs when the painted surface is exposed to chemicals such as alkalis.
Soap patches are formed on the paint surface, and the paint film gets peeled off from the surface.
PAINT APPLICATION
See Videos