Painting 101: Decorative Paint Training

Session 2: Paint Ingredients, Classification and Quality

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

  1. 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
  2. Solvent: This is a clear, volatile substance which 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 form a Clear Coating or Varnish.
  3. Pigment: This is the main solid part of the coating and consist of one or more fine, coloured powders. Two kinds of pigments are used in paints; Quality paints use more of 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.

  1. 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.
  2. 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 (2pack)
    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.

Some myths about paint quality

Oil based paints are better than water-based paints because they are more washable. NOT NECESSARILY.

Today is a time of change in the paint industry. With environmental issues coming to the fore, paint manufacturers are busy formulating new products that cut down on VOCs (volatile organic compounds) which may have adverse health effects. We now have water-based products that can match and even out-perform the ‘traditional’ durable oil-based coatings. Besides obvious advantages of water-based paints like low VOCs, easy cleanup with water, quick-drying, alkali resistance and stable non-yellowing colour over time, some products which were previously not very washable can now be formulated to be washable e.g., Vinyl Matt Emulsion and water-based products are finding more use on metals. Oil-based paints have advantages of an attractive highly washable gloss, good levelling (brush strokes fill themselves in to create a smooth finish) and a hard, durable finish. But these are far outweighed by the advantages of water-based paints and they have two major disadvantages of yellowing when used in dark areas like cupboards and they are prone to alkali attack when used directly on plaster and concrete.

Is thick paint necessarily better than a thin one?

NO. A fat guy is not necessarily healthier than a thin one! Paint maybe made thick by just adding thickener with no addition of resin or pigment. Furthermore, when you dilute thick paint you gain on covering a larger area but you lose on opacity (hence need more coats) and lose on durability because you now have less resin per litre to provide protection.

Is an expensive paint necessarily better than a cheaper one? YES.

If you are comparing paint from a single manufacturer, price and name are usually good indicators. Manufacturers need to charge more for their premium quality paint since it contains more of more costly ingredients. Price is a good indicator of quality since, a manufacturer isn’t going to charge more for a lesser quality paint (or label it as a premium paint when it’s not), since their name is on the product. Be careful when comparing products from different companies as some companies will charge more for the same quality as others simply because they are known to be market leaders!

Is there any benefit of using good quality paint? DEFINATELY.

Premium quality paint saves you time and money. If you only need to paint your house once every five years instead of every second year, you can see that paying even twice as much for quality paint, in the long run, will be less expensive in terms of labour costs, time, money and effort. Paint prices go up every year, labour charges also increase, using a good quality paint may also mean fewer coats and less labour costs if labour is charged per coat and also reduced hustles of having to move furniture or vacating your home for some days every two years instead of once every 5 years.