Choosing a Dark Paint Exterior

As dark colours and deep hues are currently in vogue with today’s design community, choice of colour is a decision frequently made by owners to achieve the desired aesthetics.

 

Before you decide on a dark colour, you should consider the possible impact that colour choice can have on the long term performance of the paint.

In general terms, lighter colours will always outperform darker colours, within the same product, environment and exposure conditions. Generally speaking, darker coloured paints absorb more UV rays than lighter coloured paints thereby putting more stress on the paint system and the substrate.

Why deep colours can be problematic?

Colour Durability – One of the many factors that influence paint durability is the choice of colour. Different colours have differing light stability. Whites have the greatest stability to UV degradation where deep hue colours (especially reds and yellows) are traditionally the most UV sensitive and therefore fade more readily.

Surface Imperfections – The combination of low “Light Reflectance Value”(LRV) deep hue colours, used in conjunction with low sheen level paint, means less light is reflected (more is scattered) hence any surface abrasions and imperfections, especially on internal surfaces, become more visible because they look shiny.

Heat Absorption – Deep hue colours have a lower LRV and reflect less light but also absorb more heat than lighter colours. This can have a detrimental effect in several ways. Hotter surfaces will cause the substrate to expand and contract more than cooler surfaces, thereby placing significantly more stress on the paint coating itself and the underlying substrate. The designer may need to include more control joints.

Some building materials actually specify a minimum LRV for the colour used, under which substrate performance will be compromised and the manufacturers’ warranty becomes null and void.

Over time, as the paint film ages, it will become less flexible and less capable of withstanding the stress and constant movement in the substrate. The destructive result can be loss of adhesion through Crazing, Cracking, Flaking, Peeling or Blistering of the paint system. Deep hue colours traditionally breakdown more quickly and have a shorter life expectancy to first maintenance, than lighter colours within the same environment.

Applying darker colours over previously painted exterior surfaces can generate more heat in the substrate, which in turn causes any moisture present to force its way out. Often the moisture travels via capillaries in the old weathered paint film to the surface but cannot escape quickly enough through the new paint film. The result is blistering of the paint film back to bare substrate requiring complete removal of all paint coatings.

Issues that can occur

Marring or Burnishing –The deeper the colour, the less white pigment (TiO2) it contains. Coloured pigments are softer than TiO2 pigment hence deep hue colours are less resistant to abrasion, marking and burnishing (polishing-up).

Pigment Transfer – Deep hue colours are more prone than lighter colours to the colour actually rubbing off and subsequent surface marking.  The soft pigment in the colourant sits close to the surface hence it is prone to marking and rubbing off. The higher the colourant level, the greater the tendency to mark.

Sheen Level – A slight drop in the sheen level of the paint may occur due to the high concentration of glycols/surfactants present in the colourants present. In some circumstances, the sheen level can appear slightly higher.

Drying Time – The speed of dry can be noticeably slowed (especially in humid conditions) by high colourant levels because the non-drying glycols/surfactants that are present act as slow evaporating solvents that keep the applied paint film wetter for a longer time period. This delayed drying time can sometimes be twice as long as expected.

Hiding Power – The Opacity of deep hue colours (especially Reds, Orange and Yellows) can be relatively poor as large quantities of the colourant are added to either Clear Base (no opacity) or Extra Bright Base (very low opacity) in order to produce a paint that has an adequate depth of colour. As little or no white pigment (TiO2) is present, the hiding power of the colour is totally reliant upon the relatively poor opacity pigments within the colourants alone.

Matching another Manufacturer’s Colour – In-store attempts to eye-match another company deep hue colours can be quite difficult and may result in excessive amounts of colourant being added.

Problems are frequently encountered when unsuspecting store-staff attempt to provide a match to a colour using another company’s tint-bases and colourants. Within a paint store, there is also no real control over the quantity of colourant being added or whether the tinting guidelines are being followed by the store staff hence there is no guarantee that the result achieved will be an accurate match to the chosen companies colour or deliver a satisfactory performance when applied.

Each paint company designs its tint-bases and colour systems to accurately produce its own colour range offer. Not all paint companies use the same colourants and rarely are the tint-bases the exact same strength, however when a paint company matches another companies colour it does so with all the scientific backup available to achieve the best possible match whilst staying within the formulating limits and guidelines, thereby minimizing the risk of poor performance.

Achieving successful results when deep hue colours are selected:

  • We minimise surprises by conducting tests before the work commences
  • We advise to ensure  completely uniform background colour is applied under deep hue topcoat colours
  • We consult with Dulux on what product will provide optimal hiding underneath the specified topcoat colour and optimal adhesion to previously painted surfaces
  • We have learnt which undercoat colours enhance the hiding power of which topcoat colours. For example, straight untinted white would be the correct undercoat colour for a bright lemon yellow topcoat colour. Red finish coats are best undercoated with a more robust hiding light grey tinted undercoat.
  • When repainting non-uniform surfaces, we ensure the correct “Tinted Undercoat” is used to totally obliterate any background colours and appearance.
  • We make sure that the selected “Tinted Undercoat” does not interfere with or adversely affect the vibrancy and/or undertone of the deep hue topcoat colour.
  • To minimize or avoid Burnishing and Marring on deep hue colour painted surfaces, we use a premium quality Wash&Wear with a Barrier Technology for built in scrub and stain resistance that allows more frequent and rigorous cleaning methods to be employed without adversely affecting the surface appearance.
  • In high traffic areas, deep hue colours are best protected by applying a high performance weather resistant clear-coat finish over the topcoat colour.
  • We follow the paint manufacturer instructions on dry time between coats.

 

This information has been sourced from Dulux Australia. 

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Modern Decor Sydney specialises in residential, office, and retail painting on Sydney’s Northern Beaches, North Shore and Eastern Suburbs.

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