What points should be specially watched when selecting suitable fluorescent and phosphorescent pigments ?
Both these types ol luminescence, i.e. fluorescence ( emission of light caused by irradation with incident light ) and phosphorescence ( fluoescence which persists after the source of incident light has been removed ) are, in fact, caused only by dyestuffs.
Pigments are dispersed in a resin matrix
. This is ground to a particle size of 2 - 4 ym as required for dispersion. Because of the resinous character of such products, luminescent pigments have relatively poor hiding power. Their effect is based on the fact that they emit light during or shortly after excitation. Such pigments are usually quite expensive because of the complexity of their manufacture. Also they are not as stable as ordinary pigments and needs occasional replacement, a fact which should be borne in mind right at the start.
