Fluorescent paint displays complex and unpredictable fading. The parameters that govern fading of fluorescent paint are multiple, and the multifaceted nature of this process is a direct consequence of fluorescent colours reflecting light whilst simultaneously emitting it. When a fluorescent pigment fades, it loses intensity in its fluorescence and hue; and the rate at which both occur is different and often difficult to predict. Usually the difference in rate of loss of fluorescence and hue, results in the fluorescent paint first darkening (due to loss of fluorescence) and then lightening as the hue of the fluorescent colour fades. This duality of fluorescent paint fading, makes colour matching a problem.
Colour matching aged fluorescent paint in a manner that allows the original media and the colour match to fade synchronously, is thus a formidable task. It is however a task that is less daunting through comprehension of the paints’ fading behaviour. In 2005 the author completed a research project on The Fading Behaviour and Colour Matching of Fluorescent Acrylic Paints. The fading behaviour of six different fluorescent pigments in acrylic binder under accelerated conditions, were monitored with spectrophotometric analysis. Reflectance and fluorescent emission spectra of each pigment were recorded weekly, and a spectral database compiled, indicative of each pigment’s fading behaviour and associated colour changes. Pure pigment samples, representative of the fluorescent acrylic paint palette tested, also underwent accelerated aging. The aged pure pigment was then mixed with acrylic binder and analysed.
Through comparison of the aged pigment in acrylic binder’s reflectance and fluorescent emission spectra, to the aged fluorescent acrylic paint’s spectra, it was ascertained that they fade at the same rate. Thus, through spectrophotometric analysis of an aged fluorescent acrylic paint layer, one could colour match and in-paint with artificially aged fluorescent pigment that has deteriorated to the same stage, yielding synchronous fading. The intention of this paper is to inform the wider conservation community of the results the author found in investigating fluorescent acrylic paint fading behaviour, and the possible strategies derived in aid of preserving works of art containing fluorescent media.