Each substrate has its own idiosyncrasies that may directly affect the performance of a paint applied to it. Fresh cementitious surfaces are highly alkaline and will attack paints that are alkali sensitive. Timbers are dimensionally unstable and require coatings with sufficient flexibility to move with the substrate. Other timbers, such as Matai, contain extractives that will prevent the drying of certain types of paints. Zinc is an alkaline metal that will cause loss of adhesion with saponifiable binders while mild steel is chemically unstable and readily oxidises. A description of the nature of the various substrata is described in the introductions of the relevant surface preparation sheets.
Our clear bright atmosphere allows a very high proportion of damaging U.V. light to reach the surface of our country. Prevailing westerlies may carry salt from the coast up to 100 kilometres inland. Thermal areas create an acidic environment as bad as the harshest European industrial areas. These and many other factors influence the performance of paint coatings. Not only are macro effects, such as those outlined important, but also micro climates exist, such as poorly ventilated bathrooms that promote mould growth; unwashed areas, such as those below steel framed canopies, which promote severe corrosion; and high temperature areas, such as may be found in certain industrial processes or in domestic conservatories, that may affect the thermoplasticity of certain coatings. A floor that is subject to only light foot traffic requires a very different treatment to a floor that takes steel wheeled trolleys; and walls in laundries, family rooms and master bedrooms each encounter significantly different levels of physical stress.
Paint systems are formulated to accommodate the idiosyncrasies of the substrate they are designed to go over, while withstanding the environment in which they must work. This may and does lead to a proliferation of paint types that may be somewhat daunting to come to terms with. However the paint industry in general and Resene in particular attempts to provide paints with the broadest possible use in order to simplify choice.
The following are some highly simplified strengths and weaknesses of certain paint categories.