Opto-thermal surface characterization of float glass

The authors report the results of a preliminary study of opto-thermal impulse response of float-glass surfaces. Remarkable differences of response were observed from the float, nonfloat and fracture surfaces, which are ascribed to near-surface impurities. Of particular interest was the discovery that nonfloat surfaces emit characteristic thermal waves, propagating from the interior to the surface. No theoretical models are currently available for describing such optothermal signals and two new data analysis programs, based on empirical expressions, were developed for this study. These reduce the decay curves to two main fitted parameters, to aid characterization and identification of unknown samples. The results illustrate the promise of opto-thermal techniques for the rapid and nondestructive identification of glass fragments in forensic investigations.