A pilot study into the use of phosphorescent sand in glass transfer studies

Phosphorescent sand is proposed as a model system to study the behaviour of glass particles and support their activity level interpretation. Pilot experiments into the properties of the phosphorescent particles indicate that they are comparable to glass. Phosphorescent particles are charged effectively using ultraviolet illumination. A prototype acquisition system was developed in which images are acquired shortly after an ultraviolet light source is switched off. An algorithm is developed to automatically segment and count particles in the acquired images. The developed method was illustrated during two series of pilot experiments. In the first series of experiments, transfer properties of glass and phosphorescent particles are compared and appear to be roughly comparable in a number of basic activities. The second series of experiments shows the transfer of phosphorescent particles in a number of activities. An intense contact in experiment led to the transfer of 9-16 % of the present phosphorescent sand particles, while a less intense contact in experiment lead to the transfer of 0-4 % of the available particles. Indirect contact by subsequent sitting on a chair, led to a transfer of < 1 % and indicated the presence of relatively large numbers of particles remaining on the bottom of the chair. A persistence experiment showed a residual of 9-55 % of present particles after one hour of regular office activity. Our pilot experiments show that the methodology is quick and versatile. It facilitates the analysis of several replicates as well as the inclusion of several validation steps in the experiments. The developed acquisition system and image processing tools are easy to use. Images can be acquired in situ, i.e. without recovery of the particles.