What is Paint?
Paint is a coloured or clear, liquid or solid substance which, when applied to a surface and exposed to heat, certain chemicals or air, converts to a dry, coherent and adherent film offering protection, etc., to the underlying substrate. Paint consists essentially of 3 main ingredients:-
Paint Ingredients
- Resin: Also called binder, medium, film former or vehicle. This is the most important and main liquid part of the coating and consists of a sticky, viscous (thick), manmade or natural substance which is used to give the coating:-
- Adhesion to the substrate makes the paint stick
- Durability – resistance to abrasion, water, chemicals, UV rays, heat, etc. makes the paint last long
- Flexibility to move with the expanding underlying substrate
- Gloss to make the paint shiny and more washable
- Solvent: This is a clear, volatile substance that readily evaporates on exposure to the atmosphere and thus forms no part of the dried coating. It is used to give the paint:-
- Ease of Application by thinning the viscosity of the resin or paint
- Penetration on substrates of low porosity
- Assists during manufacturing by thinning down the thick resin and wetting dry powder
- Modify paint physical properties like drying, smell, gloss, etc.
The combination of resin and solvent forms a Clear Coating or Varnish.
- Pigment: This is the main solid part of the coating and consists of one or more fine, coloured powders. Two kinds of pigments are used in paints; Quality paints use more good quality hiding pigments such as titanium dioxide along with small amounts of other pigments to provide the colour. Lesser quality paints use more of different types of pigments (called extenders or fillers) such as talc, clay, silica, calcium carbonate etc. along with less quantity of coloured pigments. While these may provide good hiding capabilities, they lack durability and wear quickly. Pigments provide:
- The desired Colour
- Opacity or the ability to hide or cover the underlying substrate
- Increased Protection, i.e., high build, corrosion resistance, etc.
- Texture like Eggshell or Matt
To the 3 main ingredients in the paint may be added many other ingredients in very small quantities (called Additives) to enhance or suppress specific qualities desired of certain paints, e.g., anti-foaming, biocide, thickener, drier, etc.
Paint Classification
It is very difficult to classify or group the wide variety of paints available for decorative use.
- Classification by solvent used
- Water-Based: These coatings are thinned with water, dry rapidly, relatively cheaper, better smell, thicker, heavier compared to oil-based paints and are mainly used on concrete, plaster, asbestos, etc.
- Oil-Based: These coatings are thinned with various thinners (mostly White Spirit), dry more slowly, relatively more expensive, stronger smell, generally thin, lighter than water-based paints and are mainly used on wood, metal, plastics, etc.
- Solventless: These paints have no solvent, made and used without diluting. They dry after stoving or heating or subjecting to some form of radiation. E.g., powder paints which are used for fridges, electric cookers; glass used on metallic bathtubs and Thermoline Road Marking paint.
- Other Classifications
i. Colour e.g., white, light colours, dark/deep colours, clear
ii. Finish/Texture e.g., gloss, eggshell, matt, rough, smooth, textured
iii. Market segment e.g., Decorative, Industrial, Automotive, Marine
iv. Number of components e.g., single pack, 2K (2 pack)
v. End-use e.g., Roadmarking, Swimming pool, Floor, Roof
vi. The resin used e.g., Alkyd, Epoxy, Chlorinated Rubber, PVA
vii. Method of Application e.g., Brush, Roller, Spray, Dipping
viii. Method of drying e.g., air dry, stoving, catalysed, UV cured
ix. Use in the system e.g., primer, sealer, undercoat, topcoat
It is very difficult to say which of these classifications is best since each one is more useful in one situation or another.
Paint Quality
What makes good quality paint?
Painting is an investment in product, time and labour so it is important to choose high-quality paint with a long-lasting finish. If you take the time to select high-quality paint when you begin, you will reap the benefits for many years to come. All paint companies make different grades of paints to meet different application and performance requirements.
High-quality paints provide complete coverage with fewer coats on any surface. Having high durability, they can withstand more wear and tear, scrubbing and washing than lower-quality paints, saving you time in labour and money in the product. Other paint grades with names like Professional, Architectural or General Purpose grade will work but won’t do as good a job as true premium quality paint.
High-quality paints are made with more and better ingredients than lower-quality paints, making them easier to apply, look better and last longer. Quality paints contain both the best pigments and binders, but in addition, they contain more of these ‘solids’ than lower-quality paints, and it’s the solids that remain behind after the paint has dried. Economy paints provide hiding by using less pigment then extending it with fillers that may have good hiding capability initially but lose their hiding capabilities and colour over time – particularly when exposed to weather.
Almost all high-quality paints offer one or more unique features such as extended durability, low/zero VOCs, washability, ultra-smooth finish, one-coat hide, superior touchup, mar-resistance and low odour.