Architects memo no. 14: November 1981
why semi-gloss enamels?
Full gloss enamels are glossy because they are rich in resin and low in pigment. The resin flows, like all liquids, into a smooth film, the surface of which is undisturbed by the low level of pigment floating below the surface.
This resin rich surface not only results in high gloss but also a smooth impermeable surface which is very easy to clean. This leads to the use of full gloss enamels in service areas such as kitchens, laundries and bathrooms. Technically these products perform excellently with their only drawback being that full gloss surfaces can be somewhat hard to live with. Any minor imperfections are highlighted under a gloss finish and consequently high standards of stopping and surface preparation are demanded.
The normal method of producing semi-gloss enamels is to take a paint similar to the full gloss and introduce quite a high level of extender pigments. As the resin flows in this type of system the extender pigments protrude through the surface causing loss of gloss. This method has two drawbacks: the first that protrusions are dependent on film thickness, which leads to sheeriness; the second, that the permeability is increased with a consequent reduction in the ease of cleaning.
The latest technology in semi-gloss enamels allows the reduction of the high extender levels by the introduction of polymeric flatting agents, which can produce a uniform silky flatting virtually independent of film thickness. The major advantage of this technology is that it permits a semi-gloss to be achieved without compromising permeability or cleanability. They can be safely used in all service areas and their reduced gloss is not only easier to live with, they reduce the obviousness of surface imperfections.
Although such enamels have the necessary toughness, impermeability and flexibility to provide protection out-of-doors, it must be remembered that in order to work the matting agents must be very close to the surface. It follows that the resin-rich surface present in gloss enamels is much thinner in the semi-gloss versions. The consequence of this is that less radiation can be tolerated before ‘chalking‘ commences and for this reason semi-gloss enamels are normally restricted to interior use.
Resene Lusta-Glo enamel is an example of this technology. Its beautiful soft, wax-life sheen is aesthetically very pleasing and its mar resistance excellent. These properties have led to a sharp increase in the use of this product in all service areas. We consider the importance of this product to be sufficient to be incorporated into the Resene tinting system so that it is available in all BS2660 and 5252 colours. This of course means that it enjoys the widest colour range in the country. It is available at all Resene ColorShops and other leading paint suppliers.
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