Paint in Full Colour

Paint

Not all paint is created equal. Top quality paints provide tremendous benefits. They adhere to surfaces much better and hide uneven colouration in the substrate better. They also resist chalking and colour fading, dirt and fungus better than economy paints. And despite costing more per litre, they are actually more economical since they last longer and cost less per year. Whatever surface you want to paint, there are two basic types of paint to be aware of – water-based paints and solvent-based paints.

Water-based paints

As implied, these are made using water, are often wall paints, (commonly referred to as "emulsion paints"). They are generally quick-drying, have a low odour and tend to be more environmentally compatible. When painting outside, "breathable" emulsion paints (allow moisture vapour to pass); and gives fewer blistering and peeling problems.

Solvent-based paints

Commonly used to refer to both oil and alkyd based paints, these provide a very hard smooth finish, but tend to embrittle and crack over time. Not as environmentally friendly as water-based paints, are slower to dry and give off more odour. They are more often to be found in gloss paints due to their good adhesion properties, however they are not suitable for use on galvanised metals or fresh masonry.

Solvent-Based VS Water-based

Quality exterior water-based paints provide better retention of gloss and colour than solvent-based paints, especially in sunny conditions. They also resist chalking and long-term cracking and peeling better than solvent-based products. Solvent-based paints offer superior one-coat hiding and better adhesion to difficult chalky surfaces.

Paints are made up of 4 ingredient categories:

  • Pigments - provide colour and coverage.
  • Binders - holds the pigment together and provide a tough finish which adheres well to the surface.
  • Liquids - provide desired consistency.
  • Additives - are ingredients which provide specific paint properties, for example preservatives keep the paint fresh.

As a rule of thumb, the higher the amount of pigment and binder, the better quality the paint.

Pigments:
PROVIDE COLOUR, HIDING AND BULK

Pigment is what gives colour to paint and in its raw form it is a fine powder. Pigments are finely ground particles or powders which are dispersed in paints.

There are two primary categories of pigments:

1. Prime pigments:
These are the pigments that provide whiteness and colour; they are also the main source of hiding capability. Titanium dioxide (TiO2), is the predominant white pigment.

Colour pigments provide colour by selective absorption of light. There are two main types: Organic & Inorganic

Colour pigments are compounded into liquid dispersions called colorants, which are added at the point of sale to tint bases, and to white paints designed for tinting. In the factory, colour pigments are used as dry powders and in liquid colorant form to make pre-packaged colour paints.

2. Extender pigments (or "extenders")
These provide bulk at relatively low cost. They add much less hiding than TiO2, and impact on many properties, including sheen, scrub resistance, exterior colour retention, and others. Some commonly used extenders are:
Clay, Silica and silicates, Diatomaceous silica, Calcium carbonate, Talc, Zinc oxide.

Binders:
"Binds" The Pigment, Provides Adhesion, Integrity And Toughness To The Dry Paint Film

Binder is what holds the pigment and adheres it to a surface. Some binders are used without pigments to make clear finishes and varnishes.

Oil-based and Latex Paint Binders

1. Oil-Based
The binder in an oil-based coating is made from a vegetable oil that "dries," or oxidizes, and crosslinks when it is exposed to the air, and thus develops the desired properties of the paint product. Today, few paints are made with oil alone; rather, they are based on modified oils called alkyds. Alkyds dry harder and faster than oils. The term "oil-based" is commonly used to refer to both oil and alkyd coatings.

Film Formation of oil and alkyd-based paints is a two-step process:

When the paint is applied to a surface

  • the liquid evaporates and leaves the binder and pigment on the surface; and
  • the binder then "dries" or oxidizes as it reacts with the oxygen in the air.

 the oil or alkyd paint. However, the oxidation process can ultimately  cause this type of paint to harden to the point where it is vulnerable to cracking and chipping. The oxidation also causes yellowing, which typically is bleached out by sunlight, but may be quite noticeable in an area protected from sunlight, e.g. an inside room or closet, or a wall behind a picture frame.

2. Latex-Based Binders
Most water-based paints are "latex" paints*. The binder in a latex paint is a solid, plastic-like material dispersed as microscopic particles in water. This dispersion is a milky-white liquid, which is called latex in the paint industry, in that it is reminiscent of natural latex from the rubber tree. Latex is also called emulsion, and in some countries, such as England, latex paints are referred to as emulsion paints. The paint manufacturer makes a dispersion of the pigments which will go into a batch of paint, and adds the latex binder. Thus, the paint consists of dispersed pigment and binder, along with some additives and liquid, mainly water (see sections below).

Film formation of latex paint occurs when the paint is applied and the water evaporates. During this process, the particles of pigment and binder come closer together. As the last vestiges of liquid evaporate, capillary action draws the binder particles together with great force, causing them to fuse and bind the pigment into a continuous film. This process, called coalescence, is depicted in the following graphic:

Latex Paint Film Formation

The latex paint film retains microscopic openings that allow it to "breathe", that is, allow moisture vapour to pass through. The latex paint film is thus more tolerant of moisture coming from inside the building than oil or alkyd paints, which form a "tighter" film, and are prone to blister if moisture is behind the paint, e.g., if the oil or alkyd paint is applied over damp wood or stucco.

On the other hand, latex paints may blister from rain, dew or other sources of water on the outside of the coating, if the paint:

  • has limited adhesion capability
  • was applied over a chalky or otherwise unclean surface, such that the paint's adhesion was compromised
  • has not had enough time to dry thoroughly

Under these conditions, blistering tendency will be greater if the paint has high levels of tinting colour.

As a result of these properties and benefits, 100% acrylic latex paint is often specified for use on exterior surfaces where top quality performance is required. (Acrylic binders are significantly more expensive than vinyl acrylics.)

A third category of latex binder is styrenated acrylic. Styrene is included in the binder for enhanced water resistance, gloss development and cost reduction; however, the amount of styrene that can be used is limited because too high a level can create a tendency to crack and to chalk excessively, leading to fading.

Liquids:
The Liquid Portion Of The Paint (also Referred To As The "carrier") Provides A Way To Get The Pigment And Binder From The Container Onto The Surface That Is To Be Painted
 

  • For most oil-based and alkyd paints, the liquid component is paint thinner, which is a combustible solvent made primarily of mineral spirits, a petroleum distillate of aliphatic hydrocarbons.
  • For shellac-based primers and varnishes, the liquid is denatured alcohol.
  • For clear and pigmented lacquers, the liquid is usually lacquer thinner or another solvent that is "stronger" and more flammable than paint thinner.
  • For latex paints, the liquid is primarily water (but see additives section below).

The pigments and the binder are what are left on the surface when the paint dries and the liquid portion evaporates. Together, they are called the solids portion of the paint:

Pigments + Binder = Solids
The coating (e.g., paint, stain, primer) consists of the solids and the liquid:

Solids + Liquid = Coating
When a paint is applied at a given thickness, and it then dries, the proportion of solids and liquid determines how thick the dried paint film will be:

Thus, a higher solids content can provide a thicker dry paint film , which results in better hiding and durability . For this reason, it is recommended that paints not be thinned unless necessary (such as for application by spraying), since thinning reduces the solids content of the paint per unit of volume. Latex paints generally range from 25% to about 40% volume solids, depending on type and quality. Alkyd and oil-based paints can exceed 50% volume solids.

Additives:
Additional Ingredients That Affect And Enhance Many Paint Properties

Below is a list of additives used in the manufacture of latex paints:

  • Thickeners and Rheology Modifiers
  • Surfactants
  • Biocides:  
  • Defoamers break bubbles as they are formed in the paint
  • Co-solvents are additional liquids other than water

What Makes a Quality Paint?

While most people agree that quality is better than quantity, "quality" is a confusing term. In the realm of paint, there are various grades of quality. Quality paint costs more, with the justification that it also lasts longer. But what proof is there that quality paint really is the better buy? Rohm & Haas' Paint Quality Institute answers this question all the time by looking at such things as binders, pigments and additives.

According to PQI, quality paints have better binders. The type of binder and amount used affect everything from stain and crack resistance to adhesion.

Several polymer types are used as binders for latex paints. Oil paints usually have a drying oil or a modified oil, called alkyds, as their binders. Of the two, quality latex paints with 100-percent acrylic binders are especially long-lasting. They're also more expensive.

"Part of the reason is that acrylic binders cost more," said Walt Gozdan, PQI technical director. "You're paying extra money but you're getting more durability and better adhesion."
Typically speaking, quality paints have more prime than extender pigments. Prime pigments are good hiding pigments, while extender pigments provide bulk at low cost. The most common prime pigment is titanium dioxide, a white pigment found in both oil and latex paints. It's not inexpensive but is imperative for good hiding.

Quality paints also have more additives. Additives are included in paint to provide desirable properties. They might make the paint easier to apply, for example, or give it protective qualities.

All of these benefits save time in the initial painting and in recoats. Since most of the cost of repainting a home is in labour, it makes sense to invest in a top-quality acrylic latex paint. It applies easier, lasts longer and, when spread out over the life of the paint job, costs less.

Colour

When you think Painting, the first thing that comes to mind is paint… and then colour. We are living in a century of colour, which is a showcase of our lifestyle, fashion choices, social class, economic status and leisure preferences. Other trend indicators are technology, entertainment, sustainability, socio-economic factors, globalisation and spirituality. Choosing the right colour is one of the most important parts of any paint job, and as we all know, deciding on exactly the right shade or tone can be difficult.

According to the International Colour Authority website, Colour stimulates, motivates and creates excitement. Colour is a mood and a trend setter. Fifteen years ago, 80% of paint sold was white; today it is 80% colour. We are moving from plain white to neutral colours. Colour is more and more of a lifestyle choice, so take your time and consider the latest colour trends.   

Tips:

Boundary and freestanding walls:

These areas more often than not suffer from failures caused by rising or lateral damp. We recommend that these areas are treated as maintenance items and maintained on a more regular basis. Using Masonry Paint or PVA will assist because of being more moisture tolerant than Pure Acrylics.

Colour selection:

Consult with Paint Manufacturer’s representative or specialist in choosing the correct colours. Using accent colours ads depth and contribute to overall appearance. Ask for sample panels before choosing. Samples panels must not be applied too small and should be applied to external walls exposed to natural light. Choose 3-4 colour variations for sample panels and put to vote for final selection.

Frederik Nel,
Curasure

www.curasure.co.za